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Re: Why it Pays to run Occult4
George,
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Do you feel that running Occult a day or so before a potential clear night gives more events (for that night) than my current method of running it roughly every 2 weeks covering the next month?
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I now have Aart's latest flasher design working.? It really would have taken about 1 to 2 hours except for two problems I had--one with how to load the replacement SD library correctly and the other that the GPS shield had a set-up physical switch in the wrong position.? Both of these can be avoided with some additional words in Aart's assembly procedure (or just having someone a little smarter than me doing the assembly).? Note that Aart is having me be the guinea pig for his new assembly instructions.
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Now that I've done one, additional units that I could put together would take me less than an hour each.? I think my total cost has been well less than $100 (somewhere around $90)--but I did spring for the "real" Arduino Mega instead of a cheap clone--that would reduce the cost by about $25.? If the builder has an old micro SD card, they could save the $10 I spent on that.? The antenna lead also is likely overkill, potentially saving another $3.? So the cost could end up being in the $50 to $60 range.? I did buy multipacks of pots and LEDs--so the remainder of those would be available for additional units as well.
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I still need to design and print a box to hold it, but once I do one, I can either share the file or just print some additional ones for anyone who needs one.
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While I have it running, I still need to learn a bit more about how to use it before I start testing it.? After that, I am happy to loan it out to others in our area who want to try one.
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I did get 3 clear nights this week, but no good asteroid events in my 2 week Occult run nor OW.? So I collected pre-nova spectral data on recurring nova T-CrB.? Here's some very early data if anyone is interested--note that the little peak at H-alpha is mostly caused by a feature in my reference star response curve, I need fix that...
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Steve
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Re: Why it Pays to run Occult4
4 nights later... May 25th UT
Well, a nice clear night, but - again - a near Full Moon in the sky - and no event over a 4.5% chance listed on OW Desktop. Good night to stay in. But wait... I should consult my nightly Occult4 run.... Hmmm, here's an event involving a 10.7 mag Target Star, tho it states I have a 0% chance if I observe from Home. But... if I make a short drive I'll have a 100% chance(!!!) Result -- I did have to do a 15 minute drive and hang out in a cemetery just after midnight to get it... and... the event was only 17 degrees away from the 97% lit Moon (and 17 degrees up from the horizon - just below Antares). But the 12-inch scope easily slewed right to the FOV, and the Target Star was readily apparent - and yielded a good SNR of 3.66 at 30fps with my Astrid.? ...And I had no complaints from the residents. So....., yet another example of nothing decent on OW, but consulting my nightly Occult4 search gave me a rather sure and easy event. George |
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Why it Pays to run Occult4
Once again, another very nice event - and it's nowhere to be found on either OW Desktop or OW Cloud. Here's another example of why it pays to run your own searches using Occult4.
Many events now (springtime) are quite low on the horizon (roughly... the star-rich region of Gemini is low in the west, Sagittarius is low to the south-east or south...). Many events are simply "tough", and the short nights don't help. Low and behold, I do an Occult4 search for May 21st UT and find an event involving a 10.1 mag star, and 43 degrees up (in the SE)!!! Occult 4 gives me an 88% chance. Bingo...... A very nice event. So bright in fact that I set aside my Astrid and took out the QHY174M-GPS which allowed me to capture the event at 50fps and a SNR of 8.6 (still bright at 50fps)!! Nowhere to be found on OW. Yes, I like OW.... but if you Just rely on it, you are probably missing some nice ones. George |
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Re: More on Flash Timing - Some testing...
Steve & Some...
That's great news! An assembly of an "Aart's Flasher" has parts that total less than $100! I see you aren't listing a digital display, but that may not be a necessity. Also, you have a 3D printer which most folks don't - but - I'd think a readily available "project box" (maybe $10) purchased from an electronics supply outlet would suffice as an enclosure. You also inspired me to scour my computers for some earlier testing I did using my "Aart's Flasher". I found 6 tests I ran last August (tho I know I did at least 3 times more than that). For these tests I used my QHY which embedded timestamps in each video frame (running at either 30 or 50fps), and I also put flashes from my "Aart's Flasher" on the same video. As with the OFT tests I presented above, 1 .CSV file was created and that same .CSV was first analyzed in PyOTE using timestamps, and then again using flash markers. In short, the comparisons seem to hint that a higher precision can be achieved with an Aart's GPS-based Flasher than with OFT (I'm not surprised there). These half-dozen tests seem to indicate the difference between timestamps and flash markers is a maximum of 0.0005 seconds(!). Interesting when you consider that 1/50th of a second is 0.02 seconds......... Not sure if PyOTE can calculate sub-frame timing to 1/10,000th of a second, but.... those are the numbers it listed. In some instances the measurement differences come out to 0.0000 sec(!). [I'm just reporting the actual values that PyOTE spit out folks]. A scan of test results is attached. Tho remember, flash markers only work well when the camera system doesn't drop or duplicate any frames (or at most no more than a couple). For all tests here, PyOTE reported a 0.00% timestamp error. Anyway, Steve, keep us posted on your assembly......... George |
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Re: More on Flash Timing - Some testing...
I have most of the parts for Aart's most recent flash timer design, and the rest should be here later this week.? So far, the total cost for the parts:
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Arduino clone ($19 to $22--but I sprung for the "real" Italian made one for $46 rather than the clone)
GPS shield ($30)
micro SD card (<$10)
Antenna wire lead ($3)
LED (<$1)
Potentiometer (<$1)
3D printed case (~$4 worth of PLA material, but this assumes you have access to the printer)
Mounting screws (<$5)
1220 battery ($1)
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Adding it up, looks like the parts are about $75.
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Steve
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More on Flash Timing - Some testing...
Some:
Yes, some.... This presentation may not interest most, tho maybe some... We recently had a seemingly constructive 2-hour Zoom session where we discussed getting 'new' folks involved in observing occultations. Yes, it would (certainly) be great to get a few more chords in the Northeast(!). But I think we agreed we tend to run into a stumbling block when it comes to finding an easy way for them to get started in actually timing events. Frankly it's often a notable financial outlay in the order of several hundred dollars for someone who thinks they **might** be interested, to get started. Yes, some have ample "disposable income", but many don't. For those who's pockets aren't stuffed with cash, I think this becomes a reason for them to perhaps think otherwise about getting involved. So.... I've mentioned flash timers. ...And please, I want to make it very, very clear, I do not believe they are by any means an ideal way to time occultations. However under certain circumstances they can serve a useful purpose. I see flash timers having value in two main instances: * For beginners to get STARTED - and.... * As a backup timing device [...And possibly in other "special instances"] There have existed two "flavors" of flash timers: * Flashers which reference GPS time signals - like those designed by Aart Olson, and based on an Arduino architecture - and... * Flashers which use the camera flash on a smart phone, and use NTP (Network Time Protocol) as their time base? I 'own', and have run tests on both of the above types. Currently there seem to be no readily available, "purchase-able", units along the lines of "Aarts GPS Flasher". And to make one requires some skill in electronics assembly, with parts probably costing several hundred dollars. In contrast, there has existed a flasher of the second type (NTP-based), which was once available as a free downloadable app for smart phones. I am referring to the app called "Occult Flash Tag" (herein, "OFT") - once available on Google Play and installable on Android smart phones. (As of this writing, Google Play does not offer this app, but it may again in the future).? One nice thing about OFT is/was that if a "beginner" already owns a video-capable astro-camera, and happens to have an Android smart phone in their back pocket, they could conceivably have everything they need to start timing occultations(!). But more toward the point of this post... Many "occultationists" have voiced notable reservation in basing timings on NTP. I completely agree that GPS-based timing methods should in theory have the edge over NTP. But in actual tests, just how well does and NTP (ie., OFT) perform?? I've had version 1.1 of OFT on my Android smart phone for several years now. Several years ago I ran tests at the telescope where I simulated short occultations. On each video, I had both timestamps from an IOTA-VTI, and flash markers. Recently I re-ran tests on several different nights where I again simulated an occultation, and this time each video frame was timestamped by my Astrid camera, and I also placed OFT flasher markers on the same video. All together, over the years years, I've analyzed about 45 video tests (in all tests the recorded video indicated NO timestamp errors). In short, in every test (most all done at 30fps), when D & R times derived from the timestamps were compared to D & R times derived from OFT, the agreement was within a small fraction of the exposure time of each frame. No tests had errors greater than 0.033 seconds (1 frame of standard NTSC video). So below is just an FYI post of recent comparative results... And you can draw any conclusion you wish. The attached images represent 13 out of 13 recent tests I've done (it's easier that I just scan the written pages of test results). Note: OFT has several different accuracy level settings, and for these tests it was set on the "very high accuracy" setting. Really all that needs to be looked at are the comparative times in the yellow boxes.? In short, the average deviation in time between timestamping and OFT's derived time is 0.0108 seconds. The maximum deviation is 0.0140, and the minimum deviation is 0.0070 seconds. It should be noted that each frame of video at 30 frames per second is equal to 0.0333667 seconds and PyOTE is often able to calculate a time to sub-frame accuracy.? So in short, it would seem that timings derived using OFT average to around 1/3 frame in time accuracy (when reference to video shot at 30fps). You might also notice the consistency in that OFT times are always slightly later then timestamps. I will mention that if an app such as OFT is ever used, I feel that it must be individually tested on the actual device installed before any semblance of accuracy *might* be inferred (actually, any flasher-type device should be tested against GPS timestamped video). I will also note that for any type of flash timing device, accuracy can be compromised is the recorded video has dropped or duplicate frames (so a means needs to be devised to test for this condition). Again, I am not advocating anything by presenting this, other than to simply present thoughts and test results. I'm hoping to soon do more testing on the "Aart's Arduino GPS-based flasher" I have, and perhaps present test results. George |
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Re: Flash Timer
Steve:
Interesting. Good project. I'm interested in your results. FYI, thought I'd post a couple images of the flash timer that was built for me (I mentioned by who in our Zoom chat, but I'd rather not say here - lest he get many requests...). It's based on one of Aart's flasher designs and the enclosure was 3D printed (with a magnetic detachable front). Features are: * An 8-character digital display on one side * 12VDC input jack * USB input for programming via a USB connection * Right above the USB connector is a Micro-SD card holder * A screw-in standard connector for a GPS antenna (like used on the QHY) * Black button on top is an audio buzzer * LED for the flashes on a 1-meter long wire * Unseen on the back side is a green LED indicating "GPS lock achieved". The flash times can be programmed via the USB connector, or via a text file on the Micro-SD card (which can be taken out of the unit and put in a card reader attached to a computer). The actual flashes are also logged to another text file on the Micro-SD card. Multiple events can be pre-programmed with this version. I've run several tests by putting flashes on actual timestamped videos (either by my QHY174M-GPS or Astrid), and with no dropped frames shown from time-stamping, the simulated D/R times agree to easily within 1 frame of NTSC video (0.033) seconds. If I recall most times agreed to at least 10ms. George |
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Flash Timer
After our discussion last night, I've decided to build one of Aart's flash timers.? Reasons for doing this:
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Looking through my astronomy junk drawer, I found an attempt at a flash timer I made many years back.? It consists of an Arduino Uno, Adafruit Ultimate GPS shield (with an IC, resistors, and jumpers I added), and a 2x16 LCD display shield.? I may also try to resurrect that if useable.??
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Aart has quite a number of designs in his folder in the IOTA groups.io files section.? I've emailed him to ask which he'd recommend for a beginner (for both ease of assembly and use).
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Steve
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Meeting Invite
Everyone,
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Here is the Zoom invite for tomorrow's tag-up.? Subject is recruiting and retaining new observers.
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Steve C
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Steve Conard is inviting you to a scheduled Zoom meeting.
Topic: OccultNEUS Tag-up Time: May 9, 2024 07:30 PM Eastern Time (US and Canada) Join Zoom Meeting https://zoom.us/j/93761078462?pwd=TmlYM2JGb2RUUXVOd1RiNTRaR1VXQT09 Meeting ID: 937 6107 8462 Passcode: 121931 --- One tap mobile +16465588656,,93761078462#,,,,*121931# US (New York) +16469313860,,93761078462#,,,,*121931# US --- Dial by your location ? +1 646 558 8656 US (New York) ? +1 646 931 3860 US ? +1 301 715 8592 US (Washington DC) ? +1 305 224 1968 US ? +1 309 205 3325 US ? +1 312 626 6799 US (Chicago) ? +1 386 347 5053 US ? +1 507 473 4847 US ? +1 564 217 2000 US ? +1 669 444 9171 US ? +1 669 900 9128 US (San Jose) ? +1 689 278 1000 US ? +1 719 359 4580 US ? +1 253 205 0468 US ? +1 253 215 8782 US (Tacoma) ? +1 346 248 7799 US (Houston) ? +1 360 209 5623 US Meeting ID: 937 6107 8462 Passcode: 121931 Find your local number: https://zoom.us/u/adyugZQR0n ?
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Re: Next Virtual Meeting and Makhaon Event?
I just emailed with Rick. He said....
My mistake, sorry, Thursday works for me.
Rick?
On Mon, May 6, 2024 at 10:31 AM George Viscome emailed Rick:
Rick: You said on Groups.io "Tuesday works for me". The proposed evening was Thursday. Did you mean Thursday? Tuesday evening looks potentially clear for me. George |
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Re: Next Virtual Meeting and Makhaon Event?
OK, per George's suggestion, how does Thursday evening look for everyone?? If most can make that, we'll watch the weather and if it improves we can reschedule.
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Steve
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Re: Next Virtual Meeting and Makhaon Event?
This is a good list, George.? It should keep us busy for a while.? I'd add two to it:
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--Increasing multi-chord events
--Using university and public observatories
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Steve C
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Re: Next Virtual Meeting and Makhaon Event?
Of course, I just realized I can't do the Friday Makhaon event since we have tickets for a play that night.? But it is an astronomy related play (Silent Sky), so that's not quite as bad a reason for not observing.
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Did we want to meet this evening as we all should be under clouds?? Or is that too short notice?? Monday night looks like clear skies for some of us.? I'm not available Tue and Wed this week.
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Steve
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Re: Next Virtual Meeting and Makhaon Event?
All:
I'll throw out other topics for chats.... * Astrid * Doing mobile observations and selecting sites * Carte du Ciel (I'd like to introduce you to this star/asteroid plotting program) * How to select prospective occultation events (maybe cover a bit of Occult4). * A discussion of equipment we currently use - our observatories, etc... * etc., etc.... But for the next one it might be good to talk about experiences in trying to get others involved in "oc-observing". Whenever....... ('Guess Steve will set the day/time). G |
Steve C
George Viscome
rickbria22