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Re: [29P-ml] Is anyone currently imaging 29P

 

I caught it going into outburst last night. This is the data from my 16 inch RC. I also have data from my RASAs to look at yet. This?is what I got stacking?10x30sec exposures, so at about 5 min increments. It pooped quickly!

OBSERVER: ? ?D. T. Durig
OBS CODE: ? ?V21
TELESCOPE: ? 0.4m f/8.0 Ritchey-Cretien
EXPOSURE JD: Mid-exposure, not corrected for light time
---------------------------------------------------------------
? ? ? JD ? ? ? ? mag ? ? Flt ? SNR ? ?ZeroPt ? ? ?Cat ? Design.
---------------------------------------------------------------
2460677.86963 ? 16.831 G ?C ? 44.61 ? 23.433 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.88030 ? 16.814 G ?C ? 38.34 ? 23.440 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.88386 ? 16.739 G ?C ? 54.13 ? 23.402 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.88741 ? 16.828 G ?C ? 50.67 ? 23.448 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.89097 ? 16.893 G ?C ? 50.49 ? 23.441 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.89453 ? 16.821 G ?C ? 44.84 ? 23.380 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.89808 ? 16.706 G ?C ? 45.46 ? 23.319 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.90164 ? 16.749 G ?C ? 50.32 ? 23.420 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.90520 ? 16.777 G ?C ? 48.20 ? 23.419 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.90876 ? 16.861 G ?C ? 39.38 ? 23.401 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.91232 ? 16.802 G ?C ? 46.35 ? 23.433 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.91587 ? 16.793 G ?C ? 48.14 ? 23.421 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.91943 ? 16.854 G ?C ? 50.48 ? 23.405 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.92298 ? 16.839 G ?C ? 41.78 ? 23.417 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.92654 ? 16.823 G ?C ? 45.74 ? 23.428 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.93010 ? 16.744 G ?C ? 47.40 ? 23.434 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.93365 ? 16.692 G ?C ? 52.52 ? 23.417 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.93721 ? 16.603 G ?C ? 57.56 ? 23.399 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.94076 ? 16.393 G ?C ? 64.04 ? 23.454 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.94432 ? 16.229 G ?C ? 70.49 ? 23.453 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.94788 ? 15.986 G ?C ? 81.95 ? 23.460 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.95143 ? 15.796 G ?C ? 83.74 ? 23.440 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.95546 ? 15.916 G ?C ? 85.02 ? 23.468 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.96182 ? 15.550 G ?C ? 97.70 ? 23.460 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.96892 ? 15.343 G ?C ?113.08 ? 23.442 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.97248 ? 15.241 G ?C ?121.72 ? 23.439 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.97603 ? 15.181 G ?C ?124.76 ? 23.457 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.97959 ? 15.084 G ?C ?117.40 ? 23.415 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.98315 ? 15.031 G ?C ?131.70 ? 23.440 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.98671 ? 14.944 G ?C ?133.65 ? 23.398 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.99026 ? 14.916 G ?C ?135.42 ? 23.418 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.99408 ? 14.869 G ?C ?140.90 ? 23.423 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460677.99775 ? 14.822 G ?C ?145.17 ? 23.417 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.00131 ? 14.771 G ?C ?157.13 ? 23.427 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.00487 ? 14.763 G ?C ?156.20 ? 23.431 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.00842 ? 14.752 G ?C ?156.10 ? 23.438 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.01198 ? 14.690 G ?C ?159.19 ? 23.397 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.01553 ? 14.714 G ?C ?156.24 ? 23.424 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.01909 ? 14.699 G ?C ?159.09 ? 23.401 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.02265 ? 14.714 G ?C ?159.32 ? 23.443 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.02620 ? 14.679 G ?C ?159.90 ? 23.420 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.02976 ? 14.679 G ?C ?150.27 ? 23.371 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.03331 ? 14.581 G ?C ?162.01 ? 23.302 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.03687 ? 14.647 G ?C ?163.45 ? 23.391 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.04043 ? 14.643 G ?C ?160.71 ? 23.393 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.04398 ? 14.636 G ?C ?163.00 ? 23.346 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.04754 ? 14.587 G ?C ?165.35 ? 23.299 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
2460678.05109 ? 14.567 G ?C ?164.64 ? 23.317 ? ?Gaia2 ? 29P/Schwassmann-Wachmann
----- end -----

On Thu, Jan 2, 2025 at 11:26?PM Observatory Gr?mme via <observatorygromme=[email protected]> wrote:

Dear All,

As reported?by Wayne Hawley , 29P is in outburst.
My observation from past night shows a very high Afrho value



From: [email protected] <[email protected]> on behalf of Eliot Herman via <ELIOTHERMAN=[email protected]>
Sent: Friday, January 3, 2025 2:09 AM
To: [email protected] <[email protected]>
Subject: Re: [29P-ml] Is anyone currently imaging 29P
?

I also have it scripted of a few hours from now¡­ we will see, hopefully an outburst

?

Eliot

?

From: [email protected] <[email protected]> on behalf of Wayne Hawley via <hawley.wayne=[email protected]>
Date: Thursday, January 2, 2025 at 5:17 PM
To: [email protected] <[email protected]>
Subject: Re: [29P-ml] Is anyone currently imaging 29P

I will continue imaging and I have just heard that Nick James will also be imaging for the next few hours

Regards,

?

Wayne

?

?

On Fri, 3 Jan 2025 at 00:13, Observatory Gr?mme via <observatorygromme=[email protected]> wrote:

And just as we speak, the clouds are coming in again.....?

So , make a long run observation. You are maybe on to something.. ??

?


From: [email protected] <[email protected]> on behalf of Wayne Hawley via <hawley.wayne=[email protected]>
Sent: Friday, January 3, 2025 1:11 AM
To: [email protected] <[email protected]>
Subject: Re: [29P-ml] Is anyone currently imaging 29P

?

Many thanks for confirming the?magnitude..?

?

Regards,

?

Wayne

?

?

On Fri, 3 Jan 2025 at 00:08, Observatory Gr?mme via <observatorygromme=[email protected]> wrote:

Dear Wayne,

?

Yes, i'm also observing it! And indeed a bight nucleus.

?

OBSERVER: ? ?P.-J. Dekelver

CONTACT: ? ? P.-J. Dekelver [observatorygromme@...]

TELESCOPE: ? 0.30-m f/4 Newtonian reflector

EXPOSURE JD: Mid-exposure, not corrected for light time

---------------------------------------------------------------

? ? ? JD ? ? ? ? mag ? ? Flt ? SNR ? ?ZeroPt ? ? ?Cat ? Design.

---------------------------------------------------------------

2460678.490613 ?14.488 SR SR ?89.51 ? 26.509 ? ?ATLAS2 ?0

2460678.492722 ?14.480 SR SR ?108.70 ?26.713 ? ?ATLAS2 ?0

2460678.494831 ?14.471 SR SR ?136.81 ?26.829 ? ?ATLAS2 ?0

2460678.496940 ?14.471 SR SR ?129.30 ?26.824 ? ?ATLAS2 ?0

2460678.499048 ?14.470 SR SR ?103.60 ?26.583 ? ?ATLAS2 ?0

2460678.501156 ?14.444 SR SR ?142.00 ?26.794 ? ?ATLAS2 ?0

----- end -----

?

It seems to be in outburst right now!!!!?

?


From: [email protected] <[email protected]> on behalf of Wayne Hawley via <hawley.wayne=[email protected]>
Sent: Friday, January 3, 2025 1:01 AM
To: [email protected] <[email protected]>
Subject: [29P-ml] Is anyone currently imaging 29P

?

I have taken my first few images a few minutes ago and am getting circa mag 14.3. Can anyone else confirm my readings please.?

?

Regards

?

Wayne Hawley Z09

?

?

0790 1212761


Re: [29P-ml] Is anyone currently imaging 29P

 

¿ªÔÆÌåÓý

Dear All,

As reported?by Wayne Hawley , 29P is in outburst.
My observation from past night shows a very high Afrho value



From: [email protected] <[email protected]> on behalf of Eliot Herman via groups.io <ELIOTHERMAN@...>
Sent: Friday, January 3, 2025 2:09 AM
To: [email protected] <[email protected]>
Subject: Re: [29P-ml] Is anyone currently imaging 29P
?

I also have it scripted of a few hours from now¡­ we will see, hopefully an outburst

?

Eliot

?

From: [email protected] <[email protected]> on behalf of Wayne Hawley via groups.io <hawley.wayne@...>
Date: Thursday, January 2, 2025 at 5:17 PM
To: [email protected] <[email protected]>
Subject: Re: [29P-ml] Is anyone currently imaging 29P

I will continue imaging and I have just heard that Nick James will also be imaging for the next few hours

Regards,

?

Wayne

?

?

On Fri, 3 Jan 2025 at 00:13, Observatory Gr?mme via <observatorygromme=[email protected]> wrote:

And just as we speak, the clouds are coming in again.....?

So , make a long run observation. You are maybe on to something.. ??

?


From: [email protected] <[email protected]> on behalf of Wayne Hawley via <hawley.wayne=[email protected]>
Sent: Friday, January 3, 2025 1:11 AM
To: [email protected] <[email protected]>
Subject: Re: [29P-ml] Is anyone currently imaging 29P

?

Many thanks for confirming the?magnitude..?

?

Regards,

?

Wayne

?

?

On Fri, 3 Jan 2025 at 00:08, Observatory Gr?mme via <observatorygromme=[email protected]> wrote:

Dear Wayne,

?

Yes, i'm also observing it! And indeed a bight nucleus.

?

OBSERVER: ? ?P.-J. Dekelver

CONTACT: ? ? P.-J. Dekelver [observatorygromme@...]

TELESCOPE: ? 0.30-m f/4 Newtonian reflector

EXPOSURE JD: Mid-exposure, not corrected for light time

---------------------------------------------------------------

? ? ? JD ? ? ? ? mag ? ? Flt ? SNR ? ?ZeroPt ? ? ?Cat ? Design.

---------------------------------------------------------------

2460678.490613 ?14.488 SR SR ?89.51 ? 26.509 ? ?ATLAS2 ?0

2460678.492722 ?14.480 SR SR ?108.70 ?26.713 ? ?ATLAS2 ?0

2460678.494831 ?14.471 SR SR ?136.81 ?26.829 ? ?ATLAS2 ?0

2460678.496940 ?14.471 SR SR ?129.30 ?26.824 ? ?ATLAS2 ?0

2460678.499048 ?14.470 SR SR ?103.60 ?26.583 ? ?ATLAS2 ?0

2460678.501156 ?14.444 SR SR ?142.00 ?26.794 ? ?ATLAS2 ?0

----- end -----

?

It seems to be in outburst right now!!!!?

?


From: [email protected] <[email protected]> on behalf of Wayne Hawley via <hawley.wayne=[email protected]>
Sent: Friday, January 3, 2025 1:01 AM
To: [email protected] <[email protected]>
Subject: [29P-ml] Is anyone currently imaging 29P

?

I have taken my first few images a few minutes ago and am getting circa mag 14.3. Can anyone else confirm my readings please.?

?

Regards

?

Wayne Hawley Z09

?

?

0790 1212761


Re: C/2024 G3 in outburst? - Jan 2.76, 2025 UT

 

Hi Terry and all,
My observation made earlier the same day using a remote T75 telescope in Chile didn't show anything suspicious. Just a regular brightening. Magnitude 4.7.

Comet C/2024 G3 (ATLAS)
2025 Jan. 02.36 UT ?m1=4.7: Dia.=&2.0' Tail=&19.3' in PA 242 deg... [T75] 0.25-m f/3.8 Newtonian reflector + CMOS...
T. Prystavski (iTelescope observatory, X07 (remotely from Rio Hurtado Valley, Chile))
[morning twilight: Sun alt. -12 deg]

? ?2024G3 ?2025 01 02.36 ?C ?4.7:U4 25.0L 4a ?5 & 2.0 ? ? &19.3m242 ICQ XX PRY01I ? ? C 1.98m ? ? ? ?A4B 5 U9 ? ? ? ? ? ?1.8s 1.8

best regards and clear skies,
Taras

§é§ä, 2 §ã?§é. 2025?§â. §à 22:31 terryjlovejoy via <terryjlovejoy=[email protected]> §á§Ú§ê§Ö:

I just got back from observing C/2024 G3 from a nearby bayside location in Brisbane.? This comet has been very elusive visually in 50mm binoculars due to its low elevation in twilight, but this morning I was very surprised to clearly see it binoculars complete with short tail.? Comparison with nearby 45 Oph suggested the comet's magnitude was in the 3's and subsequent photometry from the G channel using similar elevation stars confirmed a brightness of mag 3.7.? TIme of observation was 2025 Jan 2.76 UT.



--
best regards and clear skies,
Taras


C/2024 G3 in outburst? - Jan 2.76, 2025 UT

 

I just got back from observing C/2024 G3 from a nearby bayside location in Brisbane.? This comet has been very elusive visually in 50mm binoculars due to its low elevation in twilight, but this morning I was very surprised to clearly see it binoculars complete with short tail.? Comparison with nearby 45 Oph suggested the comet's magnitude was in the 3's and subsequent photometry from the G channel using similar elevation stars confirmed a brightness of mag 3.7.? TIme of observation was 2025 Jan 2.76 UT.


Re: "retirement" from visual observing

 

Alan,

"A significant factor in my decision to ¡°semi-retire¡± lies in the fact that I¡¯ve been hanging around longer and longer, and age, unfortunately, is starting to take its toll ...
...that I will likely continue to experience age-related health issues as more and more time goes by."

As a 72 years old visual observer, with several health problems in the past five years ( external ear melanoma due to 55 years of mountain activities, a kidney removed, ... ), I can understand your words well : I also will likely continue to experience age-related health issues as more and more time goes by ...

However, for the moment my eyes are still working well, and my physical condition allows me to continue visually observing comets and climbing mountains... I am thankful for that.

I have followed your astronomical career over the decades, and I can say that you are one of the great visual observers of this half century that we have passed ... Yes, it has really been a very good run ...

With all my best wishes for good health for the future,

J. J. Gonzalez Suarez
---------------------------------------------------------------------------------



On Thu, Jan 2, 2025 at 6:13?AM Alan Hale via <ahale=[email protected]> wrote:

[re-send . . . I proofread this several times before sending . . . and still . . . ]

?

Dear all,

?

Many of you may remember that, a little over three years ago, I announced that I was ¡°semi-retiring¡± from visual comet observing, At that time I wasn¡¯t entirely sure what I meant by ¡°semi-retiring,¡± but what it pretty much ended up meaning was that I cut back quite a bit on that activity, focusing primarily on bright and/or otherwise interesting comets, and decreasing my systematic observing program from three/four observations per comet per month down to more like one/two. Also, prior to that point I would try to chase down just about every faint and nondescript comet that I felt I had any chance of detecting visually, but afterwards I pretty much stopped doing that except in very rare cases.

?

A significant factor in my decision to ¡°semi-retire¡± lies in the fact that I¡¯ve been hanging around longer and longer, and age, unfortunately, is starting to take its toll. As a result of an earlier hospitalization I had already been on oxygen therapy for over three years then, plus issues with my knees and lower back were making observing ¨C which among other things entails rolling the big telescope out of its building onto a concrete observing slab ¨C more and more ¡°challenging.¡± I have nevertheless kept things up at a reduced level since that time, but as I related in an earlier post I experienced a bacterial infection and an all-but-collapsed lung back in September which resulted in my being hospitalized for three weeks (plus an additional week and a half in a physical rehab facility). I¡¯ve pretty much recovered from all that now ¨C and indeed have been active since my return home ¨C but the mere fact that I experienced all that in the first place tells me somewhat emphatically that I will likely continue to experience age-related health issues as more and more time goes by.

?

Even several years ago I was already looking at 2024 as a possible ¡°retirement¡± date, in large part due to the expected returns of 12P/Pons-Brooks and 13P/Olbers that year. Then, in 2023 Comet C/2023 A3 was discovered, offering a potential very bright comet in late 2024, and I decided I would put off any ¡°retirement¡± plans until that object had come and gone. Which it now has . . . although as I related in that earlier post, my hospitalization caused me to miss the entire morning apparition of that comet in late September/early October, and even my earliest observations after it appeared in the evening sky in mid-October were from the parking lot of the rehab facility. (That hospitalization also forced me to miss any attempt for Comet ATLAS C/2024 S1 while it was en route to perihelion. It would have been a difficult observation from my latitude and there is no guarantee any attempts would have been successful . . . but I never was even able to try.)

?

Anyway, after 55 years of essentially non-stop systematic visual comet observing that began in early 1970 when an 11-year-old kid first spotted Comet Tago-Sato-Kosaka, I have now ¡°retired¡± from that activity. I do so with my lifetime comet tally standing at 760, which includes 533 separate comets (the remainder being additional returns of periodic comets contained within that list of 533). Overall I have made 8147 visual observations of all these various comets.

?

As for what ¡°retirement¡± means . . . I¡¯m looking at this more as a ¡°transition¡± that will keep me occupied and (hopefully) productive during the coming years. I¡¯ve been imaging comets (and other objects) via the Las Cumbres Observatory for over seven years now, and I expect to keep that up (and possibly expand it). I¡¯ve focused primarily on follow-up observations of objects on the PCCP (and NEOCP) pages, and for example I was able to provide three sets of astrometric observations for Martin Macek¡¯s recent comet discovery (C/2024 Y1) that were used in its discovery announcement. I¡¯ve also successfully recovered a small number of expected periodic comets ¨C most notably 13P/Olbers ¨C and will probably keep trying my hand at that from time to time. I have been collaborating with LCO¡¯s Global Sky Partners educators¡¯ forum; these are some outstanding educators from around the world who are doing some truly amazing things. It is an honor to be associated with a group like this, and I expect to continuing working with them and assisting them in their activities whenever they need or desire it.

?

I don¡¯t necessarily intend to walk away from visual observing entirely, but anything I do from here on out will just be on an occasional rather than systematic basis, and will likely only involve bright and/or otherwise interesting comets. Indeed, if C/2024 G3 should happen to become a very bright object in about two weeks¡¯ time, I expect to be giving it a try. Over the longer haul . . . well, I promised my new wife Vickie (married for a little over four months now!) that, should she ever want to relocate closer to ¡°civilization,¡± I will not complain and will happily go along with her. For the time being she is quite content to stay in our rural location, but as we both continue to age I can foresee a time when it might become necessary for us to relocate accordingly.

?

As I have been doing for several years, I will continue to write about and post descriptions of any comets that I do manage to observe visually, and add to that lifetime tally; anyone who is interested can follow these at . As I have also done in the past, I¡¯ll continue to add events and updates from my personal life in these updates, when appropriate. Also for anyone who might be interested, I will be performing a statistical analysis of all those observations I have made of all those comets over the years, and when that is completed I will post it and activate the appropriate link on that page.

?

If you all will indulge me, before I end this post allow me to share my ¡°final¡± (at least, for now) visual comet observing session. It was the night of December 24-25; yes, that was Christmas Eve, but I didn¡¯t really contrive it that way; the skies were clear and the weather conditions were good, and I wanted to take appropriate advantage.

?

There were two comets, both of which I considered quite appropriate for a ¡°final¡± night. The first was Tsuchinshan-ATLAS C/2023 A3, which had faded quite a bit from its peak display over two months earlier and which was starting to get quite low in the western sky (indeed, it disappeared behind trees while the sky was still in astronomical twilight). When it was at its best it was the best comet I have seen during the 21st Century and, indeed, the best comet for me since the one that bears my name from over a quarter-century ago.

?

The second, and final, comet was 29P/Schwassmann-Wachmann 1, which is now diffusing out from the pair of large outbursts it underwent in November. (I took the image I posted in an earlier thread in order to document this ¡°final¡± observation.) This is by far my most-observed comet, with a total of 382 visual observations spread out over four ¡°returns.¡± My very first observation of this comet came in May 1981, while I was on a camping trip to Yosemite National Park in California; I had recently begun monitoring this comet for outbursts ¨C up to that point unsuccessfully ¨C but even though this particular outburst had taken place almost two weeks earlier, since this was back in the days when IAU Circulars were sent by snail-mail, and I had been away from home for several days, I was completely unaware that it was in an outburst phase, but nevertheless clearly detected it near 12th magnitude. I excitedly called up Dan Green the following morning, who told me that it had indeed been in outburst for quite a while; he nevertheless did end up publishing my observation ().

?

In my own mind, at least, this observation gave me full legitimacy as a comet observer; it is one thing, after all, to see a cometary phenomenon like this when one already knows about it, but another thing entirely to see it when one is completely unaware of it beforehand. (This also came during a dark and difficult time in my personal life, and it substantially helped my emotional well-being.) For many years after that I continued to monitor 29P for outbursts and detected quite a few of them; for some of these I was the first observer to report such an event. Nowadays, thanks primarily to Richard Miles and his collaborators the comet is kept under almost constant surveillance, and we now know of new outbursts as soon as they happen.

?

Anyway . . . even though I¡¯m now ¡°retired¡± from visual observing, I still plan to remain active in some capacity for at least the near- to intermediate-term future, and you¡¯ll still be hearing from me from time to time. My body is letting me know in no uncertain terms, however, that the time has come to conclude this activity and move on to whatever else may await me in this life.

?

It has really been a good run, but it¡¯s time . . .

?

?

Sincerely,

Alan

?

?


"retirement" from visual observing

 

¿ªÔÆÌåÓý

[re-send . . . I proofread this several times before sending . . . and still . . . ]

?

Dear all,

?

Many of you may remember that, a little over three years ago, I announced that I was ¡°semi-retiring¡± from visual comet observing, At that time I wasn¡¯t entirely sure what I meant by ¡°semi-retiring,¡± but what it pretty much ended up meaning was that I cut back quite a bit on that activity, focusing primarily on bright and/or otherwise interesting comets, and decreasing my systematic observing program from three/four observations per comet per month down to more like one/two. Also, prior to that point I would try to chase down just about every faint and nondescript comet that I felt I had any chance of detecting visually, but afterwards I pretty much stopped doing that except in very rare cases.

?

A significant factor in my decision to ¡°semi-retire¡± lies in the fact that I¡¯ve been hanging around longer and longer, and age, unfortunately, is starting to take its toll. As a result of an earlier hospitalization I had already been on oxygen therapy for over three years then, plus issues with my knees and lower back were making observing ¨C which among other things entails rolling the big telescope out of its building onto a concrete observing slab ¨C more and more ¡°challenging.¡± I have nevertheless kept things up at a reduced level since that time, but as I related in an earlier post I experienced a bacterial infection and an all-but-collapsed lung back in September which resulted in my being hospitalized for three weeks (plus an additional week and a half in a physical rehab facility). I¡¯ve pretty much recovered from all that now ¨C and indeed have been active since my return home ¨C but the mere fact that I experienced all that in the first place tells me somewhat emphatically that I will likely continue to experience age-related health issues as more and more time goes by.

?

Even several years ago I was already looking at 2024 as a possible ¡°retirement¡± date, in large part due to the expected returns of 12P/Pons-Brooks and 13P/Olbers that year. Then, in 2023 Comet C/2023 A3 was discovered, offering a potential very bright comet in late 2024, and I decided I would put off any ¡°retirement¡± plans until that object had come and gone. Which it now has . . . although as I related in that earlier post, my hospitalization caused me to miss the entire morning apparition of that comet in late September/early October, and even my earliest observations after it appeared in the evening sky in mid-October were from the parking lot of the rehab facility. (That hospitalization also forced me to miss any attempt for Comet ATLAS C/2024 S1 while it was en route to perihelion. It would have been a difficult observation from my latitude and there is no guarantee any attempts would have been successful . . . but I never was even able to try.)

?

Anyway, after 55 years of essentially non-stop systematic visual comet observing that began in early 1970 when an 11-year-old kid first spotted Comet Tago-Sato-Kosaka, I have now ¡°retired¡± from that activity. I do so with my lifetime comet tally standing at 760, which includes 533 separate comets (the remainder being additional returns of periodic comets contained within that list of 533). Overall I have made 8147 visual observations of all these various comets.

?

As for what ¡°retirement¡± means . . . I¡¯m looking at this more as a ¡°transition¡± that will keep me occupied and (hopefully) productive during the coming years. I¡¯ve been imaging comets (and other objects) via the Las Cumbres Observatory for over seven years now, and I expect to keep that up (and possibly expand it). I¡¯ve focused primarily on follow-up observations of objects on the PCCP (and NEOCP) pages, and for example I was able to provide three sets of astrometric observations for Martin Macek¡¯s recent comet discovery (C/2024 Y1) that were used in its discovery announcement. I¡¯ve also successfully recovered a small number of expected periodic comets ¨C most notably 13P/Olbers ¨C and will probably keep trying my hand at that from time to time. I have been collaborating with LCO¡¯s Global Sky Partners educators¡¯ forum; these are some outstanding educators from around the world who are doing some truly amazing things. It is an honor to be associated with a group like this, and I expect to continuing working with them and assisting them in their activities whenever they need or desire it.

?

I don¡¯t necessarily intend to walk away from visual observing entirely, but anything I do from here on out will just be on an occasional rather than systematic basis, and will likely only involve bright and/or otherwise interesting comets. Indeed, if C/2024 G3 should happen to become a very bright object in about two weeks¡¯ time, I expect to be giving it a try. Over the longer haul . . . well, I promised my new wife Vickie (married for a little over four months now!) that, should she ever want to relocate closer to ¡°civilization,¡± I will not complain and will happily go along with her. For the time being she is quite content to stay in our rural location, but as we both continue to age I can foresee a time when it might become necessary for us to relocate accordingly.

?

As I have been doing for several years, I will continue to write about and post descriptions of any comets that I do manage to observe visually, and add to that lifetime tally; anyone who is interested can follow these at . As I have also done in the past, I¡¯ll continue to add events and updates from my personal life in these updates, when appropriate. Also for anyone who might be interested, I will be performing a statistical analysis of all those observations I have made of all those comets over the years, and when that is completed I will post it and activate the appropriate link on that page.

?

If you all will indulge me, before I end this post allow me to share my ¡°final¡± (at least, for now) visual comet observing session. It was the night of December 24-25; yes, that was Christmas Eve, but I didn¡¯t really contrive it that way; the skies were clear and the weather conditions were good, and I wanted to take appropriate advantage.

?

There were two comets, both of which I considered quite appropriate for a ¡°final¡± night. The first was Tsuchinshan-ATLAS C/2023 A3, which had faded quite a bit from its peak display over two months earlier and which was starting to get quite low in the western sky (indeed, it disappeared behind trees while the sky was still in astronomical twilight). When it was at its best it was the best comet I have seen during the 21st Century and, indeed, the best comet for me since the one that bears my name from over a quarter-century ago.

?

The second, and final, comet was 29P/Schwassmann-Wachmann 1, which is now diffusing out from the pair of large outbursts it underwent in November. (I took the image I posted in an earlier thread in order to document this ¡°final¡± observation.) This is by far my most-observed comet, with a total of 382 visual observations spread out over four ¡°returns.¡± My very first observation of this comet came in May 1981, while I was on a camping trip to Yosemite National Park in California; I had recently begun monitoring this comet for outbursts ¨C up to that point unsuccessfully ¨C but even though this particular outburst had taken place almost two weeks earlier, since this was back in the days when IAU Circulars were sent by snail-mail, and I had been away from home for several days, I was completely unaware that it was in an outburst phase, but nevertheless clearly detected it near 12th magnitude. I excitedly called up Dan Green the following morning, who told me that it had indeed been in outburst for quite a while; he nevertheless did end up publishing my observation ().

?

In my own mind, at least, this observation gave me full legitimacy as a comet observer; it is one thing, after all, to see a cometary phenomenon like this when one already knows about it, but another thing entirely to see it when one is completely unaware of it beforehand. (This also came during a dark and difficult time in my personal life, and it substantially helped my emotional well-being.) For many years after that I continued to monitor 29P for outbursts and detected quite a few of them; for some of these I was the first observer to report such an event. Nowadays, thanks primarily to Richard Miles and his collaborators the comet is kept under almost constant surveillance, and we now know of new outbursts as soon as they happen.

?

Anyway . . . even though I¡¯m now ¡°retired¡± from visual observing, I still plan to remain active in some capacity for at least the near- to intermediate-term future, and you¡¯ll still be hearing from me from time to time. My body is letting me know in no uncertain terms, however, that the time has come to conclude this activity and move on to whatever else may await me in this life.

?

It has really been a good run, but it¡¯s time . . .

?

?

Sincerely,

Alan

?

?


"retirement" from visual observing

 

¿ªÔÆÌåÓý

Dear all,

?

Many of you may remember that, a little over three years ago, I announced that I was ¡°semi-retiring¡± from visual comet observing, At that time I wasn¡¯t entirely sure what I meant by ¡°semi-retiring,¡± but what it pretty much ended up meaning was that I cut back quite a bit on that activity, focusing primarily on bright and/or otherwise interesting comets, and decreasing my systematic observing program from three/four observations per comet per month down to more like one/two. Also, prior to that point I would try to chase down just about every faint and nondescript comet that I felt I had any chance of detecting visually, but afterwards I pretty much stopped doing that except in very rare cases.

?

A significant factor in my decision to ¡°semi-retire¡± lies in the fact that I¡¯ve been hanging around longer and longer, and age, unfortunately, is starting to take its toll. As a result of an earlier hospitalization I had already been on oygen therapy for over three years then, plus issues with my knees and lower back were making observing ¨C which among other things entails rolling the big telescope out of its building onto a concrete observing slab ¨C more and more ¡°challenging.¡± I have nevertheless kept things up at a reduced level since that time, but as I related in an earlier post I experienced a bacterial infection and an all-but-collapsed lung back in September which resulted in my being hospitalized for three weeks (plus an additional week and a half in a physical rehab facility). I¡¯ve pretty much recovered from all that now ¨C and indeed have been active since my return home ¨C but the mere fact that I experienced all that in the first place tells me somewhat emphatically that I will likely continue to experience age-related health issues as more and more time goes by.

?

Even several years ago I was already looking at 2024 as a possible ¡°retirement¡± date, in large part due to the expected returns of 12P/Pons-Brooks and 13P/Olbers that year. Then, in 2023 Comet C/2023 A3 was discovered, offering a potential very bright comet in late 2024, and I decided I would put off any ¡°retirement¡± plans until that object had come and gone. Which it now has . . . although as I related in that earlier post, my hospitalization caused me to miss the entire morning apparition of that comet in late September/early October, and even my earliest observations after it appeared in the evening sky in mid-October were from the parking lot of the rehab facility. (That hospitalization also forced me to miss any attempt for Comet ATLAS C/2024 S1 while it was en route to perihelion. It would have been a difficult observation from my latitude and there is no guarantee any attempts would have been successful . . . but I never was even able to try.)

?

Anyway, after 55 years of essentially non-stop systematic visual comet observing that began in early 1970 when an 11-year-old kid first spotted Comet Tago-Sato-Kosaka, I have now ¡°retired¡± from that activity. I do so with my lifetime comet tally standing at 760, which includes 533 separate comets (the remainder being additional returns of periodic comets contained within that list of 533). Overall I have made 8147 visual observations of all these various comets.

?

As for what ¡°retirement¡± means . . . I¡¯m looking at this more as a ¡°transition¡± that will keep me occupied and (hopefully) productive during the coming years. I¡¯ve been imaging comets (and other objects) via the Las Cumbres Observatory for over seven years now, and I expect to keep that up (and possibly expand it). I¡¯ve focused primarily on follow-up observations of objects on the PCCP (and NEOCP) pages, and for example I was able to provide three sets of astrometric observations for Martin Macek¡¯s recent comet discovery (C/2024 Y1) that were used in its discovery announcement. I¡¯ve also successfully recovered a small number of expected periodic comets ¨C most notably 13P/Olbers ¨C and will probably keep trying my hand at that from time to time. I have been collaborating with LCO¡¯s Global Sky Partners educators¡¯ forum; these are some outstanding educators from around the world who are doing some truly amazing things. It is an honor to be associated with a group like this, and I expect to continuing working with them and assisting them in their activities whenever they need or desire it.

?

I don¡¯t necessarily intend to walk away from visual observing entirely, but anything I do from here on out will just be on an occasional rather than systematic basis, and will likely only involve bright and/or otherwise interesting comets. Indeed, if C/2024 G3 should happen to become a very bright object in about two weeks¡¯ time, I expect to be giving it a try. Over the longer haul . . . well, I promised my new wife Vickie (married for a little over four months now!) that, should she ever want to relocate closer to ¡°civilization,¡± I will not complain and will happily go along with her. For the time being she is quite content to stay in our rural location, but as we both continue to age I can foresee a time when it might become necessary for us to relocate accordingly.

?

As I have been doing for several years, I will continue to write about and post descriptions of any comets that I do manage to observe visually, and add to that lifetime tally; anyone who is interested can follow these at . As I have also done in the past, I¡¯ll continue to add events and updates from my personal life in these updates, when appropriate. Also for anyone who might be interested, I will be performing a statistical analysis of all those observations I have made of all those comets over the years, and when that is completed I will post it and activate the appropriate link on that page.

?

If you all will indulge me, before I end this post allow me to share my ¡°final¡± (at least, for now) visual comet observing session. It was the night of December 24-25; yes, that was Christmas Eve, but I didn¡¯t really contrive it that way; the skies were clear and the weather conditions were good, and I wanted to take appropriate advantage.

?

There were two comets, both of which I considered quite appropriate for a ¡°final¡± night. The first was Tsuchinshan-ATLAS C/2023 A3, which had faded quite a bit from its peak display over two months earlier and which was starting to get quite low in the western sky (indeed, it disappeared behind trees while the sky was still in astronomical twilight). When it was at its best it was the best comet I have seen during the 21st Century and, indeed, the best comet for me since the one that bears my name from over a quarter-century ago.

?

The second, and final, comet was 29P/Schwassmann-Wachmann 1, which is now diffusing out from the pair of large outbursts it underwent in November. (I took the image I posted in an earlier thread in order to document this ¡°final¡± observation.) This is by far my most-observed comet, with a total of 382 visual observations spread out over four ¡°returns.¡± My very first observation of this comet came in May 1981, while I was on a camping trip to Yosemite National Park in California; I had recently begun monitoring this comet for outbursts ¨C up to that point unsuccessfully ¨C but even though this particular outburst had taken place almost two weeks earlier, since this was back in the days when IAU Circulars were sent by snail-mail, and I had been away from home for several days, I was completely unaware that it was in an outburst phase, but nevertheless clearly detected it near 12th magnitude. I excitedly called up Dan Green the following morning, who told me that it had indeed been in outburst for quite a while; he nevertheless did end up publishing my observation ().

?

In my own mind, at least, this observation gave me full legitimacy as a comet observer; it is one thing, after all, to see a cometary phenomenon like this when one already knows about it, but another thing entirely to see it when one is completely unaware of it beforehand. (This also came during a dark and difficult time in my personal life, and it substantially helped my emotional well-being.) For many years after that I continued to monitor 29P for outbursts and detected quite a few of them; for some of these I was the first observer to report such an event. Nowadays, thanks primarily to Richard Miles and his collaborators the comet is kept under almost constant surveillance, and we now know of new outbursts as soon as they happen.

?

Anyway . . . even though I¡¯m now ¡°retired¡± from visual observing, I still plan to remain active in some capacity for at least the near- to intermediate-term future, and you¡¯ll still be hearing from me from time to time. My body is letting me know in no uncertain terms, however, that the time has come to conclude this activity and move on to whatever else may await me in this life.

?

It has really been a good run, but it¡¯s time . . .

?

?

Sincerely,

Alan

?

?


Re: SOHO/STEREO comet naming

 

On 1/1/25 08:46, Maik Meyer wrote:
It is my understanding that a very large number is ready to be announced. I do not know where the bottleneck is, maybe Bill Gray or Karl Battams are able to enlighten us.
(Raises hand) I gotta admit, I'm currently the bottleneck.

There has been quite a bit of back-and-forth between me, Karl, MPC, Dan Green, and a few others on this. We've actually made a decent bit of progress on it, but much remains to be done (on my end). I think MPC and CBAT are all ready to go.

A _big_ help was Karl's recognition that the spacecraft pointing data for SOHO images is actually quite good, such that you can use the data in the FITS headers to convert pixel positions in the image to RA/decs. We'd previously assumed that to get good astrometry, we'd have to do the "traditional" thing of identifying a few stars in the image and plate-solving. That was always problematic, given that the SOHO images were not really intended for such things. You could (for example) have a few stars in one corner of the image, such that the astrometric calibration was really pretty decent there, but the comet was unfortunately in the opposite corner of the image. That would result in an obviously bad data point if you were lucky, and one close enough to be convincing (but still wrong) if you were unlucky.

Anyway. We eventually tried just using the FITS header data, getting positions for a few "known" objects, and found out that it worked quite well. It's less work on Karl's end, and we don't see bad astrometry as much anymore. Accuracy is mostly a function of ability to centroid the object, rather than due to a poor plate solution.

Also helpful was the setting of more plausible uncertainties for the astrometry. After a bit of discussion, Karl came up with a table of approximate astrometric uncertainties as a function of magnitude for the various SOHO and STEREO instruments. The basic idea is that you can measure pretty accurately within a certain magnitude range; brighter objects saturate and dimmer ones are hard to centroid. It's not as good as having measured astrometric uncertainties for each observation, but this rule-of-thumb method of saying "it's a mag 8.5 object in C2; it'll have roughly a 24-arcsecond uncertainty" was a major improvement. This is encapsulated in Find_Orb's sigma.txt file, for those interested in the details :



Find_Orb can now read the 80-column astrometry Karl generates and will output an ADES file with these rule-of-thumb sigmas. I can (usually) compute an orbit and submit the ADES and orbit to MPC. We ran a few cases past MPC and they passed muster. MPC initially had difficulties dealing with constrained orbits (they're using OrbFit), but have worked around those.

The remaining problem is that of processing a few thousand objects. At present, that's just sufficiently slow and error-prone that I'm likely to process a bunch of them and overlook a blunder in about one in twenty. I need to make the process smoother and more bullet-proof if it's going to be done on that sort of scale. I've recently finished up on a few work projects, which (I hope) will free up some time for me to (finally, after an embarrassingly long time) do this.

It will help that I've figured out what I expect to be a good way to solve orbits for short-arc Kreutz comets. These currently require a lot of fiddling about to get a solution in Find_Orb. However, I've come up with a way to determine an initial orbit for them that ought to be nearly bullet-proof. Some details below for the (probably not many) people interested in such details; I wrote this explanation up a while ago, and might as well recycle it here.

Since most of the sungrazers to be handled are, in fact, short-arc Kreutz comets, this should bring the processing time (human and computer) down to a much more manageable level.

In the end you need to measure these objects and do the orbit determination, and we speak of hundreds if not of thousands of objects. You need someone to do that and pay for this work. Also, after Brian Marsden's death these objects were no longer given as much focus as before.
That last is definitely true. MPC is tasked to do a lot of things; sungrazers are down near the bottom. I think Brian handled them because he was curious about them, but I don't think his knowledge got passed on to anybody else at MPC.

-- Bill

-------------- comment on solving Kreutz orbits -------------
... (Those not interested in details of orbit determination for sungrazers can stop now.) The idea came to me mere days ago, after looking at a plot of the actual paths of observed Kreutz comets :



I realized that the trajectory of a Kreutz is essentially constrained to be on a parabola of revolution, and all the orbits will pass through the same (almost fixed) perihelion point. Given a single observation, you have a ray that goes through that paraboloid in one or two points. You can then say that the object must have been at (almost exactly) that point, and can figure out what orbit would take it from there to the (almost) fixed perihelion point.

As noted, a ray can pierce a paraboloid in two points. But one of the orbits will have an inclination and ascending node that is Kreutz-like, and the other won¡¯t.

So in theory, that one observation is enough to let us compute a Kreutz orbit. (Looked at another way, we have the six constraints RA_observed, dec_observed, e=1, q=fixed value, B=282.81, L=35.22.) In reality, we can use it as a starting point for an improved fit using multiple observations.

The other groups (Meyer, Kracht, Kracht II, Marsden) can be handled in a mostly similar way, with the only difference being the orientation and focal length of the paraboloid. I¡¯ve hopes this will reduce the problem of ~2500 orbits from ¡°scary¡± to ¡°manageable¡±.

I think a more sophisticated analysis is possible that includes the variations caused by the sun¡¯s movement around the solar system barycenter, but am not convinced that it would help much. We¡¯re talking about objects with too few observations to really constrain an orbit, i.e., the data are pretty crummy anyway. It would be similar to including full perturbations with general relativity and 300 asteroid perturbers for an MBO where we have three days of observations.


Re: SOHO/STEREO comet naming

 

Ok, thank you for these explanations.

Adrien


Le mer. 1 janv. 2025, 19:06, karlbattams via <karlbattams=[email protected]> a ¨¦crit?:
Maik is entirely correct here. Producing orbits for SOHO (STEREO, PSP...) comets is easy. Producing orbits that are realistic is absolutely NOT easy. Anyone can test this by placing short-arc SOHO kreutz astrometry into find_orb without constraints, and letting it produce a solution. This result will be very non-Kreutz. This is the problem the MPC have/had, and this is a process Bill and I have been iterating on for some time. It's something we will be revisiting early this year. The bottom line is that I will make sure - without doubt - that all SOHO (STEREO, etc) comets get cataloged and designated, and the citizen scientist who found them credited appropriately.
?
Best wishes,
Karl


Re: SOHO/STEREO comet naming

 

Maik is entirely correct here. Producing orbits for SOHO (STEREO, PSP...) comets is easy. Producing orbits that are realistic is absolutely NOT easy. Anyone can test this by placing short-arc SOHO kreutz astrometry into find_orb without constraints, and letting it produce a solution. This result will be very non-Kreutz. This is the problem the MPC have/had, and this is a process Bill and I have been iterating on for some time. It's something we will be revisiting early this year. The bottom line is that I will make sure - without doubt - that all SOHO (STEREO, etc) comets get cataloged and designated, and the citizen scientist who found them credited appropriately.
?
Best wishes,
Karl


Re: SOHO/STEREO comet naming

 

Adrein,

For the measurements, sure somebody has to do it (it is certainly more complex than the more usual ground-based asteroid or even comet observations), but for orbit determination, if there are enough observations, why should it be difficult, while the MPC is able to deal with a far larger number of minor planets?
my experience is that with these extremely short arcs you'll often need manual interefence to make the solution converge. For instance you would fix e to 1 but also i to e.g. 142¡ã for the Kreutz group or 72¡ã for the Meyer group, etc. to nudge the solution in the correct direction. And even then you might need to do several attempts. It takes time and I do not know if this can be automated.

Maik
--
"One cannot discover comets lying in bed." * Lewis Swift
________________________________________________________________________

*** @skymorph.bsky.social


Re: SOHO/STEREO comet naming

 

For the measurements, sure somebody has to do it (it is certainly more complex than the more usual ground-based asteroid or even comet observations), but for orbit determination, if there are enough observations, why should it be difficult, while the MPC is able to deal with a far larger number of minor planets?

Adrien


Le mer. 1 janv. 2025, 14:46, Maik Meyer via <maik=[email protected]> a ¨¦crit?:
It is my understanding that a very large number is ready to be announced. I do not know where the bottleneck is, maybe Bill Gray or Karl Battams are able to enlighten us. In the end you need to measure these objects and do the orbit determination, and we speak of hundreds if not of thousands of objects. You need someone to do that and pay for this work. Also, after Brian Marsden's death these objects were no longer given as much focus as before.



Maik

Sent from my mobile

01.01.2025 14:39:15 Adrien Coffinet via <adrien.coffinet2=[email protected]>:

Hi,

Please people correct me if I'm wrong, but I think that the MPC initially decided to designate only the comets with a large enough number of observations for the orbit to be constrained well enough. SOHO comets usually have only a few observations in at most a few days and, if I'm not wrong, the resolution is not at the sub-arcsecond level that we are now used to with other observations (I think the resolution is a few tens of arcseconds per pixel, right?), so I think this is why they excluded them.

I think that, in practice, this criterion later turned mostly into the designation of only the comets with ground-based observations. Consequently, a few rare SOHO comets still get designated if they manage to be observed from the ground, but most SOHO comets are seen only by SOHO.

I think it's a bit unfortunate, especially for the SOHO comets known to have been observed at several perihelia (and therefore probably numberable), whose orbit is therefore probably fairly well constrained despite the intrinsic limitations of SOHO. The large number of SOHO comets is certainly also statistically useful even if the individual orbits are not extremely well constrained.

Adrien


Le mer. 1 janv. 2025, 13:12, Miki Kasz via <grymiki=[email protected]> a ¨¦crit?:
Why don't do SOHO comets receive MPC names after 2010? (C/YYYY {letter}{number})


Re: SOHO/STEREO comet naming

 

¿ªÔÆÌåÓý

It is my understanding that a very large number is ready to be announced. I do not know where the bottleneck is, maybe Bill Gray or Karl Battams are able to enlighten us. In the end you need to measure these objects and do the orbit determination, and we speak of hundreds if not of thousands of objects. You need someone to do that and pay for this work. Also, after Brian Marsden's death these objects were no longer given as much focus as before.



Maik

Sent from my mobile

01.01.2025 14:39:15 Adrien Coffinet via groups.io <adrien.coffinet2@...>:

Hi,

Please people correct me if I'm wrong, but I think that the MPC initially decided to designate only the comets with a large enough number of observations for the orbit to be constrained well enough. SOHO comets usually have only a few observations in at most a few days and, if I'm not wrong, the resolution is not at the sub-arcsecond level that we are now used to with other observations (I think the resolution is a few tens of arcseconds per pixel, right?), so I think this is why they excluded them.

I think that, in practice, this criterion later turned mostly into the designation of only the comets with ground-based observations. Consequently, a few rare SOHO comets still get designated if they manage to be observed from the ground, but most SOHO comets are seen only by SOHO.

I think it's a bit unfortunate, especially for the SOHO comets known to have been observed at several perihelia (and therefore probably numberable), whose orbit is therefore probably fairly well constrained despite the intrinsic limitations of SOHO. The large number of SOHO comets is certainly also statistically useful even if the individual orbits are not extremely well constrained.

Adrien


Le mer. 1 janv. 2025, 13:12, Miki Kasz via <grymiki=[email protected]> a ¨¦crit?:
Why don't do SOHO comets receive MPC names after 2010? (C/YYYY {letter}{number})


Re: SOHO/STEREO comet naming

 

Hi,

Please people correct me if I'm wrong, but I think that the MPC initially decided to designate only the comets with a large enough number of observations for the orbit to be constrained well enough. SOHO comets usually have only a few observations in at most a few days and, if I'm not wrong, the resolution is not at the sub-arcsecond level that we are now used to with other observations (I think the resolution is a few tens of arcseconds per pixel, right?), so I think this is why they excluded them.

I think that, in practice, this criterion later turned mostly into the designation of only the comets with ground-based observations. Consequently, a few rare SOHO comets still get designated if they manage to be observed from the ground, but most SOHO comets are seen only by SOHO.

I think it's a bit unfortunate, especially for the SOHO comets known to have been observed at several perihelia (and therefore probably numberable), whose orbit is therefore probably fairly well constrained despite the intrinsic limitations of SOHO. The large number of SOHO comets is certainly also statistically useful even if the individual orbits are not extremely well constrained.

Adrien


Le mer. 1 janv. 2025, 13:12, Miki Kasz via <grymiki=[email protected]> a ¨¦crit?:
Why don't do SOHO comets receive MPC names after 2010? (C/YYYY {letter}{number})


SOHO/STEREO comet naming

 

Why don't do SOHO comets receive MPC names after 2010? (C/YYYY {letter}{number})


Re: Unusual brightening of comet C/2023 Q1

 

Statistically speaking, a small percent of the low and high magnitude estimates should be thrown out and what one has left is usually the comets magnitude within the error of our visual or electronic equipment, the error of the sky conditions, the error of human manipulation of the data, the error of the coma diameter, the error of what each individual thinks is his perfectly good process of determining a comets magnitude, a multitude of other errors including a comet eruptions and what we see when those eruptions happen and for just how long. To put it nicely, with all these errors one is lucky if several different astronomers can agree on the magnitude of a comet +- one magnitude and lucky if they are actually within +- one magnitude of the actual comet magnitude. When I go to COBs database, the first thing that I look at is the observer's coma diameter for that comet, then I know how to compare my data with that observer's data. Rather than argue about coma size and magnitude, figure out a way to compute a comets actual magnitude from the data by grouping together magnitude data of similar coma sizes and applying some statistics to that data and then from the different groupings of different coma sizes determine a magnitude that might reflect a little reality. Another argument can be made about what is a reasonable coma size given the fact that there is a point at which background noise in a very large coma aperture makes magnitude measurements wrong since all the observer is doing is measuring a noise signal which is much stronger than the coma signal, regardless of what the observer may think. Rather than argue, maybe it is time to come to an agreement on a solution to make all these magnitude measurements really mean something, all one has to do is look at COBs to realize that what is happening now doesn't work or read this message thread.


Re: Unusual brightening of comet C/2023 Q1

 

Dear all,

@Peter, Alan, Michael: Thanks for your effort in detecting and confirming the
faint extended coma.

@Jakub: Thank you for appreciating my work.

I'd like to share my latest results:
2024-12-29.08 UT, m1=13.8, coma diam. 5.4', RASA 11", Weimar, 33x2min
2024-12-30.35 UT m1=13.8, coma diam. 5.7', T68 (RASA 11"), Utah, 8x3min

Please read "coma diam" as measurement aperture diameter. Uncertainty of m1
measurements is 0.1 mag (statistical error based on S/N, mainly due to
background noise).

Heavily processed (star subtracted) images are attached. Please note that
star subtraction is essential for all recent m1 estimates, e.g. on 2024-12-29.08
it appears that a star of 11th mag is less than 1' away from the comet center.

CS
Thomas

Am Mon, 30 Dec 2024 10:26:14 +0000
schrieb Observatory Gr?mme via groups.io <observatorygromme@...>:

Dear All,

My observation of C/2023 Q1 PANSTARRS:
https://www.astronomie.be/pieterjan.dekelver/Observations/2024/20241228_1749_CK23Q010_M09_FINAL.jpg

I could not see any dense coma, but the sky was foggy. A small hint of tail going to West.
[https://www.astronomie.be/pieterjan.dekelver/Observations/2024/20241228_1749_CK23Q010_M09_FINAL.jpg]


________________________________
From: [email protected] <[email protected]> on behalf of Jakub ?ern? via groups.io <kaos@...>
Sent: Monday, December 30, 2024 12:33 AM
To: [email protected] <[email protected]>
Subject: Re: [comets-ml] Unusual brightening of comet C/2023 Q1


Hello Juan and all,

I would quote your statement:

"My visual observation of C/2023 Q1 was not a highly difficult one. I made a clear detection of the very diffuse outer coma."

I would like to clarify that you believe you made a clear detection. We can either accept this at face value or not, since there are no other data that would confirm your observations¡ªexcept from Thomas, who measured nearly the same coma diameter but found the comet to be about 2.5 magnitudes fainter.

Here is a practical example: every year during the Perseids, my friend and I search for faint comets and then show them to others. There are many comets that I feel certain I can detect clearly, even though ten other people at the camp see nothing. However, my friend often confirms what I see. One might argue that experience matters¡ªthe more experienced an observer is, the more they can see. But if only two people out of many claim a detection, it might be an ¡°on-the-edge¡± observation. Another possibility is that I suggested the comet¡¯s presence to myself (knowing its position) and subconsciously convinced my friend, while there was in fact nothing visible.

How do we determine which explanation is correct?

I recall an incident in the 1990s when there was a supposed outburst reported for some comet¡ªpossibly by accident¡ªand, within a single day, three positive visual observations appeared. However, it turned out the outburst never happened. Those observers simply believed they saw a comet that wasn¡¯t there.

I remember another case in which I was personally involved: I mixed up a comet¡¯s position by a full day during a star party. Yet everyone there ¡°saw¡± the comet at the incorrect location, including three very experienced observers who each had 100+ visual observations under their belt.

Because of experiences like these, I am very cautious when someone refers to a ¡°clear detection,¡± since many factors¡ªsuch as background gradients in the field of view or varying sensitivity in different parts of the eye¡ªcan complicate visual observations. Unlike CCD images, visual observations cannot easily be re-measured by others to confirm what the observer saw.

Another difficulty is that a detection often depends on the observer¡¯s belief that something is there, and the complex eye-brain pathway can fool a person. Confirmation is challenging, even with techniques like tracking the comet¡¯s motion, because keeping a moving object centered in the field of view can sustain a gradient or pattern that the observer may interpret as a ¡°faint outer coma.¡± Its borders can be unclear and somewhat subjective.

A good approach is to avoid knowing the comet¡¯s precise position in advance and instead use a larger field, effectively attempting a ¡°blind¡± search. This can only be done if the comet has not been observed in the days before, so the observer¡¯s mind is not biased by expected positions or appearances. If a ¡°new comet¡± is drawn on a map and its coordinates align with the real comet¡¯s position, that detection can be considered quite robust.

I once had the chance to observe a comet visually from the Northern Hemisphere while simultaneously obtaining CCD images from a robotic telescope in the Southern Hemisphere. Comparing these ¡°blind¡± visual results with unknown stars and their magnitudes to the CCD measurements, I found very good agreement. Thus, I can state my visual observations were truly clear detections on that occasion¡ªbut that does not prove the correctness of any other observations.

Given the many uncertainties (eye-brain imperfections, suggestion effects, memory biases, etc.), we must approach visual measures with healthy skepticism.

What I can say is that Thomas Lehmann makes an exceptional effort to provide highly reliable total coma magnitudes from CCD data. I remember attending his lecture on his methods and noticing that his CCD observations tend to yield some of the brightest magnitudes and largest coma measurements compared to other observers. Therefore, I consider his measurements among the best in the world for confirming (or refuting) borderline visual detections.

Best regards,
Jakub ?ern?

On 29. 12. 24 21:39, jjgonzalez jjgonzalez via groups.io wrote:
Denis, Jakub, Bob, friends,

As told previously, I am tired after three consecutive nights ( Dec. 26, 27, 28 ) observing comets from the snowy Cantabrian Mountains.
So this will be a short reply ...

Denis : Quoting your words :
" ... you previously mentioned you had spoken you last words on this subject, so it is suprising to hear back from you ..."

My reply was motivated by my obvious disagreement with your previous comment [ "... in the overall description of the condition of this comet I would say that that feature ( the faint outer coma ) is a minor component of the comet ... ] and an implicit general undervaluation of the estimates of the visual observers with respect to CCD photometry.

Quoting my words : "CCD and visual data are complementary, not exclusive".

Jakub : Being really very tired, and needing a long recovery sleep, I don't want to have a long and detailed debate like in the old days, regarding the same issues comparing visual estimates and CCD measures.

But quoting your words : " Therefore, the reported visual observation may be in error¡ªeither in the estimated magnitude or the coma diameter. The observer should re-examine their observation to identify where the discrepancy arose ..."

I must say that both data ( m1, coma diameter ), and the change in position of the comet, have been verified on two consecutive nights ( Dec. 27 + 28 ),

Also from your words :
" No one is flawless¡ªmyself included."

I obviously agree ...

" ... It has been demonstrated many times that observers can report objects or details they did not actually see."

My visual observation of C/2023 Q1 was not a highly difficult one. I made a clear detection of the very diffuse outer coma.

Quoting Bob's words :
" It would be nice if we had some additional visual observers so there would be a pool of estimates to draw upon. "

These are the words I was hoping to hear, as my initial contribution to this thread was to provide the input of visual observers.

And now, really, just before going to sleep, I can seriously say that this will be my final post on this C/2023 Q1 thread.

Best regards,

J. J. Gonzalez Suarez

P.S.: I wish clear skies and good luck to those visual observers looking for the very diffuse C/2023 Q1.
-------------------------------------------------------------------------------------------------------------------------------------------------------

On Sun, Dec 29, 2024 at 9:26?PM Denis Buczynski via groups.io<> <buczynski8166@...<mailto:[email protected]>> wrote:
Bob,
It will be intersting to see your report when you are able to observe
then comet. JJ was observing from a high altitude mountain site and it
exceptional that he has been able to observe this faint (mag 15 from my
own digital observations)comet. I am not suprised there are no other
visual reports of this comet, it is faint for visual observers, but an
relatively easy target for imagers. The feat of visually observing a
faint outer coma would seem to be difficult in a comet this faint.
However according to JJ he did indeed acheive this.
Best wishes
Denis


------ Original Message ------
From: nightsky55@...<mailto:[email protected]>
To: [email protected]<mailto:[email protected]>
Sent: Sunday, December 29th 2024, 20:09
Subject: Re: [comets-ml] Unusual brightening of comet C/2023 Q1


Jakub and all,
This discussion has inspired me to observe C/2023 Q1 in my 38-cm
reflector at the next opportunity. I also have a very
dark sky especially in the north direction ¡ª when the aurora isn't
active! It would be nice if we had some additional visual observers so
there would be
a pool of estimates to draw upon. J.J. Gonzalez Suarez's observation
is the only visual sighting of the comet I'm aware of.

Bob

On Sun, Dec 29, 2024 at 1:17?PM Jakub ?ern? via groups.io<>
<kaos@...<mailto:[email protected]>> wrote:
Hello all,
If I have read the posts correctly, we have two observations:
CCD magnitude of 14.1 mag with a 5' aperture. Visual
magnitude of 11.6 mag with a 6' aperture. How can we explain
such a large difference? The CCD method measures flux in a chosen
aperture, and we know that a comet¡¯s surface brightness decreases
with distance from the central condensation. However, even if the
surface brightness is decreasing, the increase in the area of the
coma can still significantly change the total measured magnitude.
Regarding the well-known ¡°CCD vs. visual¡± issue, it often arose
in the past from insufficient exposure times, which led observers to
measure only the central condensation in a smaller aperture, whereas
visual observers saw more of the coma. Even among visual observers
alone, an ¡°aperture effect¡± has been described¡ªsmaller telescopes can
show a larger apparent coma and thus yield brighter magnitude estimates.
Hence, the 2¨C3 mag discrepancy was typically caused by different coma
sizes captured in visual vs. CCD observations. However, this problem has
largely faded in recent years as CCD observers have become more
experienced. With proper techniques, CCD observations now usually match
visual data closely, differing by only a few tenths of a magnitude due
to variations in spectral sensitivities (especially for unfiltered or
narrowband photometry vs. visual V or g' bands).
It is unlikely that a difference of 2.5 mag could arise from
nearly the same apertures (5' vs. 6'), because an increase of just 1' in
aperture should not produce such a large magnitude gap under normal
circumstances.
Although it is possible to measure an object as 2.5 mag brighter
by including a much larger coma with very low surface brightness (for
example, if the visual observation indicated a coma diameter of
15'¨C20'), this is not the situation described here. Therefore, the
reported visual observation may be in error¡ªeither in the estimated
magnitude or the coma diameter. The observer should re-examine their
observation to identify where the discrepancy arose.
No one is flawless¡ªmyself included. It has been demonstrated many
times that observers can report objects or details they did not actually
see. There have even been cases where a comet was reported at the wrong
position. We must learn from such instances in order to provide
scientifically valuable data.
Best regards, Jakub ?ern?




















Re: Unusual brightening of comet C/2023 Q1

 

¿ªÔÆÌåÓý

Dear All,

My observation of C/2023 Q1 PANSTARRS:

I could not see any dense coma, but the sky was foggy. A small hint of tail going to West.?



From: [email protected] <[email protected]> on behalf of Jakub ?ern? via groups.io <kaos@...>
Sent: Monday, December 30, 2024 12:33 AM
To: [email protected] <[email protected]>
Subject: Re: [comets-ml] Unusual brightening of comet C/2023 Q1
?

Hello Juan and all,

I would quote your statement:

"My visual observation of C/2023 Q1 was not a highly difficult one. I made a clear detection of the very diffuse outer coma."

I would like to clarify that you believe you made a clear detection. We can either accept this at face value or not, since there are no other data that would confirm your observations¡ªexcept from Thomas, who measured nearly the same coma diameter but found the comet to be about 2.5 magnitudes fainter.

Here is a practical example: every year during the Perseids, my friend and I search for faint comets and then show them to others. There are many comets that I feel certain I can detect clearly, even though ten other people at the camp see nothing. However, my friend often confirms what I see. One might argue that experience matters¡ªthe more experienced an observer is, the more they can see. But if only two people out of many claim a detection, it might be an ¡°on-the-edge¡± observation. Another possibility is that I suggested the comet¡¯s presence to myself (knowing its position) and subconsciously convinced my friend, while there was in fact nothing visible.

How do we determine which explanation is correct?

I recall an incident in the 1990s when there was a supposed outburst reported for some comet¡ªpossibly by accident¡ªand, within a single day, three positive visual observations appeared. However, it turned out the outburst never happened. Those observers simply believed they saw a comet that wasn¡¯t there.

I remember another case in which I was personally involved: I mixed up a comet¡¯s position by a full day during a star party. Yet everyone there ¡°saw¡± the comet at the incorrect location, including three very experienced observers who each had 100+ visual observations under their belt.

Because of experiences like these, I am very cautious when someone refers to a ¡°clear detection,¡± since many factors¡ªsuch as background gradients in the field of view or varying sensitivity in different parts of the eye¡ªcan complicate visual observations. Unlike CCD images, visual observations cannot easily be re-measured by others to confirm what the observer saw.

Another difficulty is that a detection often depends on the observer¡¯s belief that something is there, and the complex eye-brain pathway can fool a person. Confirmation is challenging, even with techniques like tracking the comet¡¯s motion, because keeping a moving object centered in the field of view can sustain a gradient or pattern that the observer may interpret as a ¡°faint outer coma.¡± Its borders can be unclear and somewhat subjective.

A good approach is to avoid knowing the comet¡¯s precise position in advance and instead use a larger field, effectively attempting a ¡°blind¡± search. This can only be done if the comet has not been observed in the days before, so the observer¡¯s mind is not biased by expected positions or appearances. If a ¡°new comet¡± is drawn on a map and its coordinates align with the real comet¡¯s position, that detection can be considered quite robust.

I once had the chance to observe a comet visually from the Northern Hemisphere while simultaneously obtaining CCD images from a robotic telescope in the Southern Hemisphere. Comparing these ¡°blind¡± visual results with unknown stars and their magnitudes to the CCD measurements, I found very good agreement. Thus, I can state my visual observations were truly clear detections on that occasion¡ªbut that does not prove the correctness of any other observations.

Given the many uncertainties (eye-brain imperfections, suggestion effects, memory biases, etc.), we must approach visual measures with healthy skepticism.

What I can say is that Thomas Lehmann makes an exceptional effort to provide highly reliable total coma magnitudes from CCD data. I remember attending his lecture on his methods and noticing that his CCD observations tend to yield some of the brightest magnitudes and largest coma measurements compared to other observers. Therefore, I consider his measurements among the best in the world for confirming (or refuting) borderline visual detections.

Best regards,
Jakub ?ern?

On 29. 12. 24 21:39, jjgonzalez jjgonzalez via groups.io wrote:
Denis, Jakub, Bob, friends,

As told previously, I am tired after three consecutive nights ( Dec. 26, 27, 28 ) observing comets from the snowy Cantabrian Mountains.
So this will be a short reply ...

Denis : Quoting your words :
" ... you previously mentioned you had spoken you last words on this subject, so it is suprising to hear back from you ..."

My reply was motivated by my obvious disagreement with your previous comment [ "... in the overall description of the condition of this comet I would say that that feature ( the faint outer coma ) ?is a minor component of the comet ... ] and an implicit general undervaluation of the estimates of the visual observers with respect to CCD photometry.

Quoting my words : "CCD and visual data are ?complementary, not exclusive".

Jakub : Being really very tired, and needing a long recovery sleep, I don't want to have a long and detailed debate like in the old days, regarding the same issues comparing visual estimates and CCD measures.

But quoting your words : " Therefore, the reported visual observation may be in error¡ªeither in the estimated magnitude or the coma diameter. The observer should re-examine their observation to identify where the discrepancy arose ..."

I must say that both data ( m1, coma diameter ), and the change in position of the comet, have been verified on two consecutive nights ( Dec. 27 + 28 ),

Also from your words :
" No one is flawless¡ªmyself included."

I obviously agree ...

" ... It has been demonstrated many times that observers can report objects or details they did not actually see."

My visual observation of C/2023 Q1 was not a highly difficult one. I made a clear detection of the very diffuse outer coma.

Quoting Bob's words :
" It would be nice if we had some additional visual observers so there would be a pool of estimates to draw upon. "

These are the words I was hoping to hear, as my initial contribution to this thread was to provide the input of visual observers.

And now, really, just before going to sleep, I can seriously say that this will be my final post on this C/2023 Q1 thread.

Best regards,

J. J. Gonzalez Suarez

P.S.: I wish clear skies and good luck to those visual observers looking for the very diffuse C/2023 Q1.
-------------------------------------------------------------------------------------------------------------------------------------------------------

On Sun, Dec 29, 2024 at 9:26?PM Denis Buczynski via <buczynski8166=[email protected]> wrote:
Bob,
It will be intersting to see your report when you are able to observe
then comet. JJ was observing from a high altitude mountain site and it
exceptional that he has been able to observe this faint (mag 15 from my
own digital observations)comet. I am not suprised there are no other
visual reports of this comet, it is faint for visual observers, but an
relatively easy target for imagers. The feat of visually observing a
faint outer coma would seem to be difficult in a comet this faint.
However according to JJ he did indeed acheive this.
Best wishes
Denis


? ? ? ? ------ Original Message ------
? ? ? ? From: nightsky55=[email protected]
? ? ? ? To: [email protected]
? ? ? ? Sent: Sunday, December 29th 2024, 20:09
? ? ? ? Subject: Re: [comets-ml] Unusual brightening of comet C/2023 Q1


? Jakub and all,
? This discussion has inspired me to observe C/2023 Q1 in my 38-cm
reflector at the next opportunity. I also have a very
? dark sky especially in the north direction ¡ª when the aurora isn't
active! It would be nice if we had some additional visual observers so
there would be
? a pool of estimates to draw upon. J.J. Gonzalez Suarez's observation
is the only visual sighting of the comet I'm aware of.

? Bob

? On Sun, Dec 29, 2024 at 1:17?PM Jakub ?ern? via
<kaos=[email protected]> wrote:
? ? ? ? ? ? ? ? ? ? ? Hello all,
? ? ? ?If I have read the posts correctly, we have two observations:
? ? ? ?CCD magnitude of 14.1 mag with a 5' aperture.? ? ? ?Visual
magnitude of 11.6 mag with a 6' aperture.? ? ? ? ? How can we explain
such a large difference? The CCD method? ? ? ?measures flux in a chosen
aperture, and we know that a comet¡¯s? ? ? ?surface brightness decreases
with distance from the central? ? ? ?condensation. However, even if the
surface brightness is? ? ? ?decreasing, the increase in the area of the
coma can still? ? ? ?significantly change the total measured magnitude.
? ? ? ?Regarding the well-known ¡°CCD vs. visual¡± issue, it often arose
in the past from insufficient exposure times, which led observers to
measure only the central condensation in a smaller aperture, whereas
visual observers saw more of the coma. Even among visual observers
alone, an ¡°aperture effect¡± has been described¡ªsmaller telescopes can
show a larger apparent coma and thus yield brighter magnitude estimates.
Hence, the 2¨C3 mag discrepancy was typically caused by different coma
sizes captured in visual vs. CCD observations. However, this problem has
largely faded in recent years as CCD observers have become more
experienced. With proper techniques, CCD observations now usually match
visual data closely, differing by only a few tenths of a magnitude due
to variations in spectral sensitivities (especially for unfiltered or
narrowband photometry vs. visual V or g' bands).
? ? ? ?It is unlikely that a difference of 2.5 mag could arise from
nearly the same apertures (5' vs. 6'), because an increase of just 1' in
aperture should not produce such a large magnitude gap under normal
circumstances.
? ? ? ?Although it is possible to measure an object as 2.5 mag brighter
by including a much larger coma with very low surface brightness (for
example, if the visual observation indicated a coma diameter of
15'¨C20'), this is not the situation described here. Therefore, the
reported visual observation may be in error¡ªeither in the estimated
magnitude or the coma diameter. The observer should re-examine their
observation to identify where the discrepancy arose.
? ? ? ?No one is flawless¡ªmyself included. It has been demonstrated many
times that observers can report objects or details they did not actually
see. There have even been cases where a comet was reported at the wrong
position. We must learn from such instances in order to provide
scientifically valuable data.
? ? ? ?Best regards,? ? ? ?Jakub ?ern?















NEW OBSERVATIONS - Observatory Gr?mme MPC: M09 - 2024-12-28

 

¿ªÔÆÌåÓý

Dear Co-Observers,

?

NEW OBSERVATIONS ¨C 2024-12-28


Unexpectedly i had a fairly clear / faint fog evening of 28 December before heavy fog ruined the night again.?



About the possible outburst or significance increase in brightness of comet C/2023 Q1 PANSTARRS: i cannot confirm this.?
My sky was too foggy to see any very diffuse coma. I measure a steady magnitude of 15.4 m1 using KOPR.

Images on the website!

?

*** Equipment ***

0.30-m f/4 Newtonian reflector + CCD FLI Microline KAF3200ME / 10Micron GM2000HPS

Detailed information about equipment and scientific information inside the image.


Best Regards,

Mr. Pieter-Jan Dekelver

Oudsbergen, Belgium

observatorygromme@...

Observatory Gr?mme - MPC: D09 ¨C M09


Re: C/2024 G3

 

thanks a lot for the detailed explanation Qicheng!?

Nicolas

Le?lun. 30 d¨¦c. 2024 ¨¤?00:33, Qicheng Zhang via <qzalaska=[email protected]> a ¨¦crit?:
My estimate of the dynamical age is based on the (inbound) semi-major axis, which is ~4000 au for this comet. Comets with such a semi-major axis of a few thousand au can often become gravitationally unbound from the solar system by planetary perturbations in just a single apparition, where each such passage can randomly deliver a momentum kick up or down depending on exactly when the comet passes through the planetary region. Comets straight from the Oort cloud are essentially right on the edge of being gravitationally bound/unbound originally, so comets like C/2024 G3 are ~1 typical momentum kick in, while an older comet like C/2023 P1 with a semi-major axis of only ~60 au must have passed through the planetary region many, many more times to have received enough of these kicks to shrink its orbit down so much more.

For a proper analysis, you'd need to run a bunch of orbital simulations with clones of this comet on the same orbit, but shifted in perihelion time to measure the probability distribution for the momentum kick expected per apparition. It's quite hard to change the near-perihelion portion of a long period comet's orbit since gravitational perturbations tend to only significantly impact the aphelion distance/orbital period, whereas there aren't any significant perturbation sources stronger than the galactic tide/passing stars, which only really become significant out into the Oort cloud. Therefore, it's reasonably accurate to treat the dynamical evolution process of most long period comets as just random walks starting from the Oort cloud, and you can work out the probability distribution/expected value for the number of apparitions/momentum kicks any comet has had based on the typical kick size and how far the comet is from being unbound. That said, the typical kick size for most cometary orbits through the inner solar system that don't pass particularly close to Jupiter (or any other big planet) tends to be fairly similar. From having just looked at a bunch of these comets, I've found those with semi-major axes of several thousand au, like C/2024 G3, tend to be ~1 kick inward from the Oort cloud, so are statistically likely to have only made one to a few prior passages through the planetary region.

Note also that both old and young comets can be either dust or gas rich, although observational surveys seem to indicate older comets (especially at low q) overall tend to be less dusty than younger comets. Dynamically old comets also do tend to brighten more steadily than new ones, but that's more of a consequence of comets behaving differently on their first time through the inner solar system than afterward, and also because the dynamically new population contains a lot of tiny/unstable comets far smaller than what can survive near the Sun, whereas most of these tiny/unstable comets are destroyed within one apparition, leaving only the large/stable comets and a relatively smaller number of borderline surviving/less stable comets that may or may not survive again in the returning comet population.

Qicheng

On Sunday, December 29, 2024 at 08:41:46 p.m. UTC, Nico Lefaudeux via <nicolas.lefaudeux=[email protected]> wrote:


Hi Qicheng, hi all,
i am curious about which information can tell that the comat has "a dynamical age on the order of only ~1 orbit" ? I thought the orbit analysis could only tell the previous aphelion distance, and little about the previous perihelia.
Seeing that the comet seems to be very "gas depleted" and almost purely dusty, with a smooth light curve (without steps associated with volatiles "switching on"), i was thinking this was pointing?toward the comet having already seen at least a handful of very close perihelia (or many perihelia at larger distance).
i would be glad to learn more about how one can tell if a long-period comet has been near the sun only one or a few times compared to many times.
Nicolas


Le?sam. 28 d¨¦c. 2024 ¨¤?20:06, Qicheng Zhang via <qzalaska=[email protected]> a ¨¦crit?:
The comet's absolute magnitude is ~7, so it's technically brighter than the Bortle limit for all q. Of course, it's also dynamically old, but with a dynamical age on the order of only ~1 orbit, and disintegration isn't too abnormal for such comets, even when brighter than the Bortle limit. C/2021 A1 was a recent example that comes to mind. But many also do survive, like C/2002 V1.

A narrow dust spine (at least before perihelion, as in the present case) means there's now considerable dust being released at very low velocity, which requires that dust be from a source far from the nucleus (as outflowing gas would push any dust near the nucleus itself at high velocity into the main coma). That suggests the comet started to disrupt, with fragments breaking off and drifting away from the nucleus before crumbling further into the low velocity, spine-forming dust. This sort of structure is likely also responsible for the triangular shape the gas coma of a disrupting comet often takes, but this comet may be too dusty for its gas coma to be seen.

At the moment, the comet still has a large, primary coma, which indicates there's at least one large, active nucleus present. If the large coma fades out in favor of the spine (which is a distinct possibility, but far from guaranteed at this point), that would signal the end of this nucleus.

Qicheng

On Saturday, December 28, 2024 at 12:29:58 p.m. UTC, Nick James <comets@...> wrote:


Hi all,

I have been observing C/2024 G3 for the last few weeks using T70 at X07
in Chile. This instrument is able to get down to the mountain ridge
horizon which is around 4 degrees at that azimuth and the sky
transparecy at X07 is very good. T70 is a very short FL instrument
(actually a Samyang 135mm FL lens) but it is good for magnitude
estimates of bright comets although the astrometry I get from the images
is a bit ropey.

This morning (Dec 28.35) I had a total magnitude of 6.0 unfiltered using
Comphot and Gaia DR3 G mags. Michael's estiamate at around the same time
using T75 was 5.8 (taken from COBS). These are fitting the lightcurve
well so there is no sign of any abnormal activity at the moment.

Using astrometry from the MPC up to December 23 and my more recent
astrometry with the 135mm lens there appears to be no obvious
improvement to the residuals by including non-gravitational forces. This
was using Findorb.

My image from this morning is here:



Other images and data are here:



Here's hoping that this comet survives to provide a nice display
post-perihelion. Sadly, us northern observers won't get much of a chance
to see it so we will be relying on reports from the southern hemisphere.

Nick James. BAA Comet Section.

On 28/12/2024 07:42, Michael Mattiazzo via wrote:
> Howdy Folks,
>
>?
>
> C/2024 G3 ATLAS has been kept under extensive observation by several observers, despite its poor location.
>
> Attached a light curve showing a steady brightening toward perihelion that could see it reach magnitude -3, if it survives.
>
> I¡¯ve also attached? images from Dec 25 and 26 showing a curious spine feature (often seen in outbursting comets) but this comet is not in outburst.
>
> Hopefully there is sufficient nuclear material to keep going. It is a very dusty comet as seen with the parabolic hood.
>
> This situation reminds me of C/2002 V1 NEAT in March 2023
>
>?
>
> Cheers,
>
> Michael
>
>
>
>
>
>
>