Re: ST4 Guide Port action
Dear all,
Thanks Gary to have explained the way the guiding correction works.
You say "The way ST4 applies guiding is to add a fixed amount (programmed in GUIDE 2 speed value....".?
OK
Then in his message /g/ServoCAT/message/7395 I see Gabriel has lowered the guidespeed in ServoCAT Sky to 6 arc seconds per second to achieve a good auto guidingBut I see at same time the classical guide2 values are around 160 arc sec/sec for obsessions scopes, whatever their diameter, which is very far away from the 6 arc sec/sec that found Gabriel.
There is a conflict here : if the guide2 value is 6 arc sec/sec for autoguiding, it will be way too slow for visual observing.
Gabriel, how do you manage this if you want to observe visually ?
Changing the rate settings in servocat sky each time you change from autoguiding to visual would be boring...
With your guide 2 being 6 arc seconds/sec, did you change your guide 1 speed -which is classicaly in the 250-280 arc sec/sec - to 160 arc sec/sec to use it for visual observation ? Then you also need to reajust the slew and jog rates also to have smooth ratio change...
In this case the guide 2 will be only allocated to autoguiding and guide 1, slew, jog for visual observing.... Right ???
Unless I miss something ???
Regards?
Rapha?l
Gabriel : I send you a private email to discuss your scope settings and avoid polluting this group. I hope you have received it.
?
|
Autoguiding is now working as it should
At last guiding works as intended and without changing the settings wildly or going against PHD2 recommendations.
?
From the last time out I have tightened the screws on my guidescope which caused it to shift slightly, so the main scope is pointing to the lower right corner of the guidescope fov, which is not much of a compromise since i just have to pick the closest guidestar in that corner instead of the center.
?
In ServoCAT Sky? i have set backlash comp to 0 on alt and az, lowered the guidespeed in ServoCAT Sky and the Meade Generic driver to 6 arc seconds per second (0.40 x Sidereal).
?
I also created a new profile in PHD2 where it detected the 0.40 x Sidereal guidespeed from the Meade driver.
?
It was windy outside, the type of wind that makes me very skeptical to even give imaging a try but i gave it a shot anyway!
?
PHD2 calibration was completed without any warnings, and after running the guide assistant it recommended min mo of 0.12 in RA/AZ and 0.19 in DEC/ALT. So i followed that.
?
I tried guiding first to the north at 38 degrees altitude, then to the east at 50 degrees altitude, in both cases, despite the windy conditions i got 1.0-1.3 RMS guiding in arc seconds. Similar error in both axis and round stars in the test exposures.
?
The guiding graph looked similar to my 200PDS on the Sky-Watcher EQ mount without any large deflections apart from a windgust here and there,?
?
Then the clouds rolled in! Can't wait for the next clear night hopefully without any wind!
?
Moral of the story: Read the PHD2 documentation:
?
From the trouble shooting document:
"YouTube videos, unless done by someone close to the PHD2 project, have wildly variable quality, often reflecting misunderstandings and sometimes producing a witches' brew of good and bad advice - so be careful what you watch.? One of the most common mistakes is to wildly change the PHD2 guiding parameters in a futile attempt to correct for mechanical problems that exist in your setup. ?This only makes things worse. The default guiding parameters calculated by PHD2 reflect the parameters you entered in the new-profile-wizard, so they are already adjusted for your setup. You should be able to get reasonable results out-of-the-box if the equipment behaves and if you don't, you are probably dealing with operational mistakes or mechanical problems"
?
Edit: I did however follow the below alt/az PHD2 guide (unchecked multi-star guiding and changed the ALT/DEC guiding algorithm to Hysteresis etc)
?
?
?
|
Re: ST4 Guide Port action
Hello Gary,
?
Thank you for the info, interesting and helpful! I have read some about guiding on Cloudy nights and it seems other systems do the same, they add to the current track rate, so when they mention "0.5 x sidereal" they have stated that the current rate increases or decreases by 7.52 arc seconds, as i am writing this i realize that EQ mounts always are very close to the sidereal rate which would mean that the guidespeed would have to be greater than 1x sidereal for the RA to change directions, that explains why you can't enter more than 1.01x sidereal in the PHD2 guide section, and why backlash only was a problem in DEC when i used my EQ mount.
?
By the way, i saw some posts about the Mesu 200 mount with ServoCat Argo with insane tracking accuracy, so it seems, like i think you have written somewhere already - the scope and installation is the limiting factor not the ServoCAT when it comes to Astrophotography.
?
/Gabriel
|
Gabriel,?
Just a note on how the ST4 guide port works as implemented in the ServoCAT.?
First off both the AZ and the ALT tracking rates are changing continuously on an ALT/AZ mount. They will go from zero as, for example, AZ crosses over directly south in which case the ALT will go from UP through 0 speed and then back to down... it will of course be decrementing (on the east side of the meridian) and slowly incrementing on the west side. I believe the equivalent location in the sky for the same action only in the AZ axis is at a position of 90 - LAT in both AZ and ALT. So if you are at 40¡ã LAT it would be at a position of AZ=50, ALT = 50. Just below that in ALT and the AZ will be slowing down, just above that it will be speeding up.?
Second of course if you reverse direction you will due to the nature of mechanics in gearing, introduce backlash and have to unwind the gears going in the opposite direction.?
The way ST4 applies guiding is to add a fixed amount (programmed in GUIDE 2 speed value and used only when the HC is in GUIDE and the command is coming from/through the ST4 port). It does not replace the actual track rate. It simply modifies it. So if at a particular location in the sky the AZ track rate is 12.52123 arcsecs/second and the ST4 AZ GUIDE 2 speed is 10 then an ST4 command to go west (in the direction of sidereal movement) the track speed will increase to 22.52123. If the east command came in it would go to 2.52123. So it speeds up - or it slows down. NOTE however that if the ST4 rate were, for example, 15, then in one direction it would go to 25.52123 and in the other direction it would go negative to -3.47877 AND in the process lash will be introduced.?
Hindsight says I should have designed it not to go below 0 speed... but it is what it is currently (and there are more than likely additional complications if it were done that way).?
So you can see that ideally the GUIDE speed (ST4) values should, as well, be fluid as the AZ changes drastically going through infinity as one approaches dead-center to the zenith and passes through it. In 0 time it has to go from pointing directly east to directly west. Because of this for any and all factors related to tracking with a dob - avoid the pole! It works extremely well visually even as high as say 86¡ã Alt... but you're getting in to some very high numbers and rapid changes so from an imaging standpoint I'd stay a good distance from the pole - probably a good 10 - 15 degrees away.?
If I were to do it again, now having actually used it and experimented with it... it would be different than what it is. But when i did it very few were using it (I had a handful of people that would talk about it over nearly 20 years or so). But now that CMOS cameras have made very short exposures possible (down to sub 1 second on very large apertures) it becomes something that ideally would be optimized.?
I don't say this as any pressure on Bill.... he is doing fantastic work both in keeping up production as well as working on new and exciting products... but maybe a "what could I have done... " statement on my own part and accordingly: an explanation of what I did probably way way back in about 2004 or so.?
Gary Myers
------ Original Message ------
Date 2/14/2025 9:47:26 AM
Subject Re: [ServoCAT] Promising Autoguiding results in PHD2
[Edited Message Follows]
I would also like to take the opportunity to correct myself. I have now read the PHD2 documentation (mostly the troubleshooting section) and according to what is written there, if you get large/abrupt guidestar deflections like i was getting, wildly changing the settings in PHD2 is not likley to solve the problem, at least not in the long run, it is almost always due to hardware issues which should always be adressed first.?
?
This is what the PHD2 documentation states about the symptoms i had:
?
Large/Abrupt Guide Star Deflections
Most users eventually encounter situations where the guide star appears to make a large, abrupt excursion away from the lock-point. ?The great majority of these problems?arise from neither the mount nor?PHD2's guide commands. ?Instead, they usually come from?unwanted mechanical movement in the gear that is riding on top of the mount, especially the guide camera/guide scope assembly. ?This is especially true if the large deflections occur in declination because the Dec motor is normally idle except for executing the very short, relatively infrequent guide commands it receives. ?The unwanted mechanical movement usually comes from several sources:
- Tiny movements of the various components in the guiding assembly as a result of the changing gravitational forces while the mount tracks the target object
- Dragging, binding, or snagging of cables, especially those that are connected to the guide camera
- Wind gusts or less commonly, effects from camera filter changes, auto-focusing, or mirror movement
- Use of mount features for backlash compensation - these should not be used with PHD2 guiding
Before rejecting these things as likely sources of? problems, think again about the tiny measurement scales and tolerances described in the previous section. ?With many guiding set-ups, a movement of only 5 microns can create an apparent tracking error (guide star deflection) of over 6 arc-sec, the equivalent of many star diameters. Every mechanical interface, every set-screw, every movable element has the potential to shift or move on its own by these tiny amounts. ?Even when cables have been routed in a purposeful way, they may bind or pull in certain sky positions or after a meridian flip. ?Cable ties or ribbed plastic cable guides hare small protrusions that can briefly catch on stationary parts of the mount. ?For large Dec deflections, it's easy to determine if these things are coming into play. ?Just use the PHDLogViewer tool to zoom in on the time of interest and see if the deflection was immediately preceded by a correspondingly large guide command in the direction of movement. ?In most cases, you will find this didn't happen. ?It can sometimes happen at the beginning of a guide session if you're using PHD2 Dec backlash compensation, but those events should disappear quickly. ?If the abrupt deflections occur in RA, the analysis is less straightforward because the RA motor runs continuously. ?But even then, unusually large, randomly space deflections are more likely to arise from the sorts of mechanical problems described here than from errors in the RA drive system.
?
?
So i took a closer look at how my guidescope is mounted and it could be a problem, i have tightened the screws and we will se if it makes a difference.
?
Guidespeed was probably also the problem in the beginning and just to see what will happen next time i will try 10 arc seconds /per second in ServoCat Sky, which is actually what the link with the Panther mount recommends and also the defualt value in the Meade Generic driver.
?
I also read in the documentation that you should not change the guidespeed in PHD2 "manually" you should reset and create a new profile where that is entered in the first steps, i noticed that if i enter 10 arc seconds per second in the Meade Driver and in the beginning in PHD2 when creating the profile, PHD2 does not change it to 1.01 arc seconds like i wrote earlier so now both the Meade driver, PHD2 and ServoCAT sky has 10 arc seconds /per second, i hope it clears up tonight so that i can give it a try! (i have also set backlash comp to 0 on both axis in ServoCat Sky this time)
?
In the first calibration, If the measured guidespeed in PHD2 turnes out to be say 5 arc seconds per second instead of 10, then i will re-do the profile and enter the new speed (0.33 x Sidereal in that case) so that the correct guide-pulse length is calculated for calibration and guiding.
?
Here is the PHD2 user guide: https://openphdguiding.org/PHD2_User_Guide.pdf
?
/Gabriel
?
?
|
Re: Promising Autoguiding results in PHD2
Thanks Gabriel,
clear !!!
|
Re: Promising Autoguiding results in PHD2
I have seen very few images taken with dobs that have been autoguided, i can only remember one and that was on an EQ platform from Tom O, so i have only read about 2 that have succeded in doing this in alt/az (Dan Price, and another Obsession owner).
?
So you don't need autoguiding, and you don't need to take even 10 second exposures, with a modern low read noise camera you can get away with 3 seconds even.
?
The fact that your guidescope has a long focal length is a lot better than the 50mm guidescope i am using which only has 180mm focal length, even if they are not perfectly aligned i would still give it a try and see the results, then you know for sure (if you want to try autoguiding).
?
The only reason i am trying to autoguide is because i am having great fun problemsolving and i am very fascinated bu the subject of tracking accuracy, it may even be difficult to tell the difference on my future images even if i get autoguiding to work well.
?
Even if the guidescope and mainscope are not pointing at the same spot in the sky, as you are indicating i suspect you can still keep the object reasonably centered probably for even more than 30 minutes, then you would just re-center and pick a new guidestar.
?
/Gabriel
?
?
|
Re: Promising Autoguiding results in PHD2
Thanks Gabriel for clarification.
You indicate your unguided precision is "0.08 arc seconds per axis per second".
In the last session I did to improve my ratio, I measured initially a 0.05 arc seconds per second in az and 0.32 arc seconds per second in alt.?
I have then calculated at home the correction factor and the new ratio in alt and az have been put in servocat but bad weather then.
I will check next time I have good weather at observatory what are my new az and alt precision. But I will certainly be globally not that far from you on precision.
I then have some questions :
?
* I see wonderfull pictures taken with alt/az scopes here. Are these pictures taken using the autoguiding method ? Or with unguided scopes ? In the latter case what is your precision of these unguided scope in arc sec/ sec ??
Because I wonder if, as a newbie in astrophoto, autoguiding is necessary or not...
If I read correctly your initial message Gabriel, I understand that you have improved precision of guiding by a factor 2 when using the autoguiding method (from 2-2.5 arc" to 1.3 arc " for your exposure time of <13"). It this improvment necessary for a newbie ?
?
* I have a 10" (f=1150 mm) scope in // of the 36" (f=3150 mm). This could be used for autoguiding, no ?
The only potential problem is that the parallellism of the 2 scope may vary a little bit when I change location in the sky because the 10" is fixed by its back on a plate (with adjustment screw at back of the plate to parallelize the 10"), and I believe a little bit of flexion occurs certainly. Not a big deal in visual, but in astrophoto I don't know...  Maybe on a given zone of the sky it will not change its flexion for a total 30 min posing? I don't know...
?
Thnaks for your feedback
Rapha?l
?
|
Re: Promising Autoguiding results in PHD2
I would also like to take the opportunity to correct myself. I have now read the PHD2 documentation (mostly the troubleshooting section) and according to what is written there, if you get large/abrupt guidestar deflections like i was getting, wildly changing the settings in PHD2 is not likley to solve the problem, at least not in the long run, it is almost always due to hardware issues which should always be adressed first.?
?
This is what the PHD2 documentation states about the symptoms i had:
?
Large/Abrupt Guide Star Deflections
Most users eventually encounter situations where the guide star appears to make a large, abrupt excursion away from the lock-point. ?The great majority of these problems?arise from neither the mount nor?PHD2's guide commands. ?Instead, they usually come from?unwanted mechanical movement in the gear that is riding on top of the mount, especially the guide camera/guide scope assembly. ?This is especially true if the large deflections occur in declination because the Dec motor is normally idle except for executing the very short, relatively infrequent guide commands it receives. ?The unwanted mechanical movement usually comes from several sources:
- Tiny movements of the various components in the guiding assembly as a result of the changing gravitational forces while the mount tracks the target object
- Dragging, binding, or snagging of cables, especially those that are connected to the guide camera
- Wind gusts or less commonly, effects from camera filter changes, auto-focusing, or mirror movement
- Use of mount features for backlash compensation - these should not be used with PHD2 guiding
Before rejecting these things as likely sources of? problems, think again about the tiny measurement scales and tolerances described in the previous section. ?With many guiding set-ups, a movement of only 5 microns can create an apparent tracking error (guide star deflection) of over 6 arc-sec, the equivalent of many star diameters. Every mechanical interface, every set-screw, every movable element has the potential to shift or move on its own by these tiny amounts. ?Even when cables have been routed in a purposeful way, they may bind or pull in certain sky positions or after a meridian flip. ?Cable ties or ribbed plastic cable guides hare small protrusions that can briefly catch on stationary parts of the mount. ?For large Dec deflections, it's easy to determine if these things are coming into play. ?Just use the PHDLogViewer tool to zoom in on the time of interest and see if the deflection was immediately preceded by a correspondingly large guide command in the direction of movement. ?In most cases, you will find this didn't happen. ?It can sometimes happen at the beginning of a guide session if you're using PHD2 Dec backlash compensation, but those events should disappear quickly. ?If the abrupt deflections occur in RA, the analysis is less straightforward because the RA motor runs continuously. ?But even then, unusually large, randomly space deflections are more likely to arise from the sorts of mechanical problems described here than from errors in the RA drive system.
?
?
So i took a closer look at how my guidescope is mounted and it could be a problem, i have tightened the screws and we will se if it makes a difference.
?
Guidespeed was probably also the problem in the beginning and just to see what will happen next time i will try 10 arc seconds /per second in ServoCat Sky, which is actually what the link with the Panther mount recommends and also the defualt value in the Meade Generic driver.
?
I also read in the documentation that you should not change the guidespeed in PHD2 "manually" you should reset and create a new profile where that is entered in the first steps, i noticed that if i enter 10 arc seconds per second in the Meade Driver and in the beginning in PHD2 when creating the profile, PHD2 does not change it to 1.01 arc seconds like i wrote earlier so now both the Meade driver, PHD2 and ServoCAT sky has 10 arc seconds /per second, i hope it clears up tonight so that i can give it a try! (i have also set backlash comp to 0 on both axis in ServoCat Sky this time)
?
In the first calibration, If the measured guidespeed in PHD2 turnes out to be say 5 arc seconds per second instead of 10, then i will re-do the profile and enter the new speed (0.33 x Sidereal in that case) so that the correct guide-pulse length is calculated for calibration and guiding.
?
Here is the PHD2 user guide: https://openphdguiding.org/PHD2_User_Guide.pdf
?
/Gabriel
?
?
|
Re: Promising Autoguiding results in PHD2
Hello Raphael
Glad it is of interest!
?
2.0-2.5 arc seconds unguided for my sub exposure time which? is 10-13s with only a slice of time from 1 night as reference so would need more nights to verify and i don't know the tracking accuracy for the images i have aquired so far. The Fullum alt/az scopes look really cool, exiting times ahead if you try imaging!
?
When it comes to the mesuread drift rate it was generally around 5 arc seconds per minute per axis so that would be 0.08 arc seconds per axis per second = total of 0.16 arc seconds drift error per second. If you take 0.16 arc seconds x 13 seconds = 2.08 arc seconds so the numbers agree fairley well.
?
Best regards
Gabriel
?
?
|
Re: Promising Autoguiding results in PHD2
Thanls Gabriel,
Really appreciate how you share your experience !
Try astrophotography using my 36" Fullum alt/az is a target for future and with your explainations it becomes clearer what to do.
And the ressource is really great !
I'm currently in the gear ratio tracking improvement phase, which you pointed out to be a must have before thinking of astrophoto.
When you say "the unguided performance seems to be about 2.0-2.5 arc seconds RMS" I believe this error of 2.0-2.5 arc seconds is for a amount of time, right ?
Per seconds ?
For example you measured that the unguided star was drifting in the field for 20' in 10 min and so 20*60=1200 arc second in 10min so? 1200/(10*60)=2 arc seconds / s, right ?
Just curious what accuracy you achieved to compare with my actual precision of tracking.
Regards
Rapha?l
|
Re: Promising Autoguiding results in PHD2
I appreciate your gratitude Mickey, luckily the hard work has also been very interesting and rewarding!
?
/Gabriel
|
Re: Promising Autoguiding results in PHD2
Thank you Gabriel for the hard work and time you put in in this project so far.? ?I am hopeful to use this in some way with my rig, using SharpCap. We will see.
Thank you Mickey
toggle quoted message
Show quoted text
On Feb 12, 2025, at 6:59?AM, Gabriel Wiklund via groups.io <gabriel.wiklundholeshot@...> wrote:
? Thanks to the moon i have been able to dedicate the last 3 clear nights on getting autoguding to work with my ServoCat driven 30" F3.4 Starstructure dob.
?
The first night i used a guidespeed of 25 arc sec/sec then 20 arc sec/sec in ServoCat Sky, no matter what i did with the settings in PHD2 the guide corrections would cause the scope to shake similar to wind gusts which showed up in the subs as double or triple stars.
?
On night 2 i used a guidespeed of 15 arc sec/ sec, this time the guiding looked pretty good but it kept loosing the guidestar after some time so i suspect that one of the motors was changing directions = backlash which caused the loss in tracking.
?
The above scenario is similar to what i have seen a few others run in to trying to autoguide with their dobs after searching the internet.
?
Then it struck me, that the guidespeed PHD2 was measuring was not the same as in the PHD2 calibration section.
?
The measured guidespeed was about 0.44 x Sidereal when using 15 arc sec/sec in ServoCat sky, but in the PHD2 section 1.01x Sidereal was set.
Which means that the calibration guide pulse length was calculated for twice the actual guidespeed = the calculated pulses for calibration and guiding would be way shorter than they should be.
?
So i changed the guidespeed in the PHD2 section to 0.44 x Sidereal, (does not change it in the mount, only for calculations). For the value to stay it is essential that you don't connect PHD2 with the mount, so one should connect to "ask for coordinates". If you connect to the mount, at least with the Meade Generic driver, it will automatically change to 1.01x in PHD2.
?
So i calibrated once again and this time the guiding looked like something i could work with by only changing the settings in PHD2.
?
On a sidenote to my great surprise PHD2 could always calibrate during all my attempts these 3 nights with almost no Orthogonality error or any warnings except the "DEC and RA rates varied by an unexpected amount" which went away after i entered the correct guidespeed in the calibration section. For calibration i trie both bright and dim stars and always at an altitude between 30 and 40 degrees which the Alt/az enthusiast Niels Haagh recommends in his alt/az PHD2 guide: /?
?
So with that out of the way the tweaking began, i ran the guide assistant which only recommended that i should lower the min move on both axis which did not make sense since that causes more aggressive guiding.
?
After a while the picture started to become clear, if you want to guide "a huge ship" you can't do that by bouncing it around like a small stick, the stick will instantly settle but the huge ship will start to oscillate and you will loose control. If the ship starts to drift, you want to cancel out the drift, then slowly bring it back on track.
?
Finally i found settings that where able to give me guiding around 1.3" arc seconds RMS. Tracking accuracy unguided was about 2.0-2.5 arc seconds. Alt and Az drift rates where at about 5 arc seconds per minute for each axis. In reality the improvement manifested as many 10s subs in the 2.6-3.0 FWHM range guided, if i remember correctly no unguided subs where below 3.0 FWHM.
?
Here are the settings i used:
Default MinMo on both axis is 0.20. I raised this to 0.40 so that the guider does not correct just because of slight deviations.
Default Hysteresis on both axis is 0.10. I set this to 0 since i don't want the guider to repeat previous corrections to avoid risk of oscillations.
Default RA and DEC Agression is 0.70 on both axis, i lowered this to 0.20-0.40 depending on conditions to avoid too agressive corrections.
Default Max Guidepulse duration on RA and DEC is 2500 ms, i set this as low as 50-400 ms depending on conditions in order for the guider to slowly bring back the scope to the guide star and not send a long pulse to quickly center the star.
?
Of course every rig is different, the difference may even be huge but summarized the key to autoguiding a large dob seems to be to first of all get the unguided tracking as good as possible with the 2-star and very accurate gear ratios and then use a slow guidespeed and short guidepulses since the opposite will cause too much movement which will not settle like on a small scope.
?
For guiding i used a 50mm guidescope, 120MM Mini guidecamera and ST4 cable. Using 180mm of focal length on the guidescope to guide the main scope at 2725mm is of course insanity but this is how i see it:
?
The guiding setup is good enough to verify if the guiding is about 0.8" arc seconds RMS, so it will be able to provide corrections that exceed my mounts unguided performance.
?
However, since the platescale of my setup is 0.297 arc seconds per pixel it is of course impossible for a 50 mm guidescope to make corrections within such a small tolerance, but this is a dob not a CDK 700 or ASA 800 and even if my scope would be able to stay witin 0.297 arc seconds it would not be seen since the seeing here is to bad, in the same way the seeing also hides tracking errors.
?
As for field rotation the guidescope and main scope are pointing at the same spot, or rather i know which spot on the Bullz eye in PHD2 my main scope is pointing. The chances of a guidestar being on that exact same spot are not big, but here is how i see it:
?
I like watching the subs roll in, so if the object starts to drift in the main scope i can re-center. If you want to sleep then NINAS re-center after drift will take care of that and PHD2 will automatically pick a guidestar and start guiding again after the re-center.?
?
I find it interesting that i have so far been able to image and get decent results despite the fact that the unguided performance seems to be about 2.0-2.5 arc seconds RMS.
?
I wonder though, how much in all this is the star moving because of seeing vs the scope itself moving, and when it comes to guiding it is of course strongly affected by seeing conditions.
?
It will be interesting to see how this evolves in the coming sessions!
?
Clear Skies
Gabriel
?
?
?
|
Promising Autoguiding results in PHD2
Thanks to the moon i have been able to dedicate the last 3 clear nights on getting autoguding to work with my ServoCat driven 30" F3.4 Starstructure dob.
?
The first night i used a guidespeed of 25 arc sec/sec then 20 arc sec/sec in ServoCat Sky, no matter what i did with the settings in PHD2 the guide corrections would cause the scope to shake similar to wind gusts which showed up in the subs as double or triple stars.
?
On night 2 i used a guidespeed of 15 arc sec/ sec, this time the guiding looked pretty good but it kept loosing the guidestar after some time so i suspect that one of the motors was changing directions = backlash which caused the loss in tracking.
?
The above scenario is similar to what i have seen a few others run in to trying to autoguide with their dobs after searching the internet.
?
Then it struck me, that the guidespeed PHD2 was measuring was not the same as in the PHD2 calibration section.
?
The measured guidespeed was about 0.44 x Sidereal when using 15 arc sec/sec in ServoCat sky, but in the PHD2 section 1.01x Sidereal was set.
Which means that the calibration guide pulse length was calculated for twice the actual guidespeed = the calculated pulses for calibration and guiding would be way shorter than they should be.
?
So i changed the guidespeed in the PHD2 section to 0.44 x Sidereal, (does not change it in the mount, only for calculations). For the value to stay it is essential that you don't connect PHD2 with the mount, so one should connect to "ask for coordinates". If you connect to the mount, at least with the Meade Generic driver, it will automatically change to 1.01x in PHD2.
?
So i calibrated once again and this time the guiding looked like something i could work with by only changing the settings in PHD2.
?
On a sidenote to my great surprise PHD2 could always calibrate during all my attempts these 3 nights with almost no Orthogonality error or any warnings except the "DEC and RA rates varied by an unexpected amount" which went away after i entered the correct guidespeed in the calibration section. For calibration i trie both bright and dim stars and always at an altitude between 30 and 40 degrees which the Alt/az enthusiast Niels Haagh recommends in his alt/az PHD2 guide: /?
?
So with that out of the way the tweaking began, i ran the guide assistant which only recommended that i should lower the min move on both axis which did not make sense since that causes more aggressive guiding.
?
After a while the picture started to become clear, if you want to guide "a huge ship" you can't do that by bouncing it around like a small stick, the stick will instantly settle but the huge ship will start to oscillate and you will loose control. If the ship starts to drift, you want to cancel out the drift, then slowly bring it back on track.
?
Finally i found settings that where able to give me guiding around 1.3" arc seconds RMS. Tracking accuracy unguided was about 2.0-2.5 arc seconds. Alt and Az drift rates where at about 5 arc seconds per minute for each axis. In reality the improvement manifested as many 10s subs in the 2.6-3.0 FWHM range guided, if i remember correctly no unguided subs where below 3.0 FWHM.
?
Here are the settings i used:
Default MinMo on both axis is 0.20. I raised this to 0.40 so that the guider does not correct just because of slight deviations.
Default Hysteresis on both axis is 0.10. I set this to 0 since i don't want the guider to repeat previous corrections to avoid risk of oscillations.
Default RA and DEC Agression is 0.70 on both axis, i lowered this to 0.20-0.40 depending on conditions to avoid too agressive corrections.
Default Max Guidepulse duration on RA and DEC is 2500 ms, i set this as low as 50-400 ms depending on conditions in order for the guider to slowly bring back the scope to the guide star and not send a long pulse to quickly center the star.
?
Of course every rig is different, the difference may even be huge but summarized the key to autoguiding a large dob seems to be to first of all get the unguided tracking as good as possible with the 2-star and very accurate gear ratios and then use a slow guidespeed and short guidepulses since the opposite will cause too much movement which will not settle like on a small scope.
?
For guiding i used a 50mm guidescope, 120MM Mini guidecamera and ST4 cable. Using 180mm of focal length on the guidescope to guide the main scope at 2725mm is of course insanity but this is how i see it:
?
The guiding setup is good enough to verify if the guiding is about 0.8" arc seconds RMS, so it will be able to provide corrections that exceed my mounts unguided performance.
?
However, since the platescale of my setup is 0.297 arc seconds per pixel it is of course impossible for a 50 mm guidescope to make corrections within such a small tolerance, but this is a dob not a CDK 700 or ASA 800 and even if my scope would be able to stay witin 0.297 arc seconds it would not be seen since the seeing here is to bad, in the same way the seeing also hides tracking errors.
?
As for field rotation the guidescope and main scope are pointing at the same spot, or rather i know which spot on the Bullz eye in PHD2 my main scope is pointing. The chances of a guidestar being on that exact same spot are not big, but here is how i see it:
?
I like watching the subs roll in, so if the object starts to drift in the main scope i can re-center. If you want to sleep then NINAS re-center after drift will take care of that and PHD2 will automatically pick a guidestar and start guiding again after the re-center.?
?
I find it interesting that i have so far been able to image and get decent results despite the fact that the unguided performance seems to be about 2.0-2.5 arc seconds RMS.
?
I wonder though, how much in all this is the star moving because of seeing vs the scope itself moving, and when it comes to guiding it is of course strongly affected by seeing conditions.
?
It will be interesting to see how this evolves in the coming sessions!
?
Clear Skies
Gabriel
?
?
?
|
Re: Starstructure/Servocat/Nexus Astro images since 5/12-24
I downloaded your image as a *.png and then did some Pixinsight + BlurXTerminator + NoiseXTerminator + StarXTerminator + GHS.? Then did some predistortion in GIMP, then went back to Pixinsight and added back the stars with Pixelmath.
?
I exaggerated the blacks by using the Linear shift in GHS (Generalized Hyperbolic Stretch).
?
While some may dislike the tedium of post processing, I find it "almost" as fun as capturing the image myself.
?
Richard
?
|
Re: Starstructure/Servocat/Nexus Astro images since 5/12-24
Beautiful image Gabriel. Unless you wish to go thru the mind numbing exercise of full deconvolution in any post processing program and then not have it work the way you hoped (& that will be the case) then have to go thru the full on steps for star corrections (this will take hours for both) I suggest you use Seti Astro's Cosmic Correct or RC Astro's Blue Xterminator. These programs where designed & written so we would not have to spend hours star correcting and deconvoluting then have it not turn out the way we want. These 2 programs do this in a matter of seconds or go ahead and spend many many days learning how to use a deconvolution and star correcting methods then after months of learning spending hours on each image running those programs. ? As for other steps in post processing I did learn the hands on step by step method and or studied what, how and why those steps worked. In my opinion reading and studying what, how and why decon and star correct work is a good idea, trying to learn, master and then implement those processes is a waste of very valuable time. Why do you think a master processor like Adam Block and Russ Croman along with others were so thrilled when RC came out with Blur Xeterminator?? Because they "who knew how to decon and star correct" didn't have to spend endless hours to use those very imperfect programs.
My soap box 2 cents worth.??
Mickey
Here is my latest image: 1073x 10s (2h 50m) on NGC 2336. Distance about 100 million light years. Data from 2 nights (Thurs-Fri & Sat-Sun).
?
High res:
?
I have thought a bit about the chromatic aberration, it actually does not bother me much, and a hardware solution
or correct processing would be more inspiring than using AI, nothing wrong with using AI but solving problems
without the help of AI is a fun challenge for me personally. I thought i was alone on thinking like this but noticed a
youtube channel started "The real intelligence challenge" I saw one image of M33 posted on Astrobin contending.
?
/Gabriel
|
Re: Starstructure/Servocat/Nexus Astro images since 5/12-24
Here is my latest image: 1073x 10s (2h 59m) on NGC 2336. Distance about 100 million light years. Data from 2 nights (Thurs-Fri & Sat-Sun).
?
High res:
?
I have thought a bit about the chromatic aberration, it actually does not bother me much, and a hardware solution
or correct processing would be more inspiring than using AI, nothing wrong with using AI but solving problems
without the help of AI is a fun challenge for me personally. I thought i was alone on thinking like this but noticed a
youtube channel started "The real intelligence challenge" I saw one image of M33 posted on Astrobin contending.
?
/Gabriel
|
To close out this thread¡ Sunday night we set up and then the dew and clouds came rolling in. We just kept everything covered, no observing, no testing. We probably won¡¯t be out until the end of this month. So, lets close out this thread, and see what happens next time. ? Thanks everyone for the help. Steve Goldberg ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Steve Goldberg via groups.io
Sent: Sunday, February 2, 2025 9:04 AM
To: [email protected]
Subject: Re: [ServoCAT] Runaway tracking? And good morning to you, too. FYI for future reference, we both have the 15" Obsession Classic. "Dueling Telescopes" As for s/w versions of our SC, I doubt they are the latest. I'll have to figure out / find somebody that can update the scopes. I have a new AN, but Amelia's AN is probably an older version. When I talked about Amelia's going to the horizon, the tube was actually horizontal to the ground.So the rocker box stopped it. She tried to get to it for a 3-button stop but couldn't in time. I think I remember seeing the AN guide number with <down arrow> number so it still wanted to go more. At that point she said turn off the AN and she'll observe without tracking. Now we know we can try going to another object and keep going. As for my HC, coming out of the HC is a coiled extension cable, with a RJ connector to the cable at the top of the stalk. I think the problem is one of the RJ pin wire at this connector point. Today I will try your suggestion trying to locate the issue. My gut felling it is NOT inside the HC or SC box. Whew.. Thanks again for the reply and things to try. On 02/02/2025 7:39 AM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote: Good morning Steve and Amelia, Ok ... so mostly good operation last night. A few comments re what you posted: -any 'drift' might be caused by not having done the backlash compensation. Is Amelia's scope and AN set up for the latest versions? If not you might want to upgrade to those as there were significant adds to each of them.? -When you say - and I know its a day later and it looks like you didn't know even then, when you say "go below the horizon"... what does that mean? The AN doesn't actually say that. Do you mean it had an offset for a GOTO that would have taken it below the horizon? With the latest version (and I believe earlier ones) the system would not allow a GOTO below the horizon - the AN would do a down beat - bee...booooooop telling the user that it was indeed an object below the horizon. There is no need to stop using the system at that point - just go to an object that is not below the horizon. Not sure why she gave up. IF you think that indeed as I suggested might be the case for the loooong GOTO's the night before - there might be a slipping DSC encoder, you could at that time (or any time) go to MODE ALT AZ and see if the ALT is indicating it is below the horizon. The AN and ServoCAT have LOTS of protections built in re the horizon. For example if you are tracking an object that sets - the ALT tracking will stop at the horizon (the AZ will continue on). And as mentioned it won't allow a GOTO to an object below the horizon. Further remember that the horizon is as the AN sees it to be from the initial alignment. IF there is a slipping encoder this would of course mess with that potentially. Also - there is a parameter, I believe under SETUP GOTO that allows you to set a local horizon limit. So for example if you have trees all around that limit visibility to no lower than 20¡ã you can program that in. That will then become the local horizon limit. I have mine set to I believe 12¡ã just because I don't want to look through 10+ atmospheres near the horizon nor jeopardize the main mirror moving (tipping).? -re your Gen3 HC. You might want to invest in a spare HC cable. Bill can sell that to you or you can find it online (unknown quality) by looking for a handset cable with a 4 pin RJ22 connector wired as a 'voice' cable.? If it is the connector inside the HC or inside the ServoCAT that would be more work - but that is extremely rare.? You can test the cable by plugging it in (during the day is fine) ... looking at the lights on it. After power up (all lights turn on briefly as a check) it should go to the red GUIDE fast light being on as well as the green GOTO. Wiggle the cable at one end a bunch of times and see if it restarts (lights off and then all lights back on briefly). Repeat at both ends. If one end seems to do this action, and you're sure of it, then reverse the cable and try again at THAT end of the CABLE. So - you have it plugged in and wiggle the HC end. Nothing happens. You wiggle the ServoCAT end and it seems to cause the HC lights to reset... hold THIS end of the cable - unplug it and move it to the HC - THIS end is the suspicious end... plug in the now free end to the CAT. Now repeat by wiggling at the HC. If it does it again then it is indeed the cable. If not - and it does it again by now, again, wiggling at the ServoCAT then its the ServoCAT connection. Contact bill if you suspect it is a fixed connection and not the cable. My strong suspicious is it is the cable.? ------ Original Message ------ Subject Re: [ServoCAT] Runaway tracking Sorry I didn't see this before the evening so couldn't do the test. We did, however, during the day unplug / replug all the data cables, from the 2 motors and the main box. We couldn't do the cable on the AZ motor with the plastic cover. Just could get my hands on it. 1. Last night everything went almost perfect. The tracking wasn't steady, had a slight drift that Amelia could live. NOTHING like we had seen the night before. 2. Later in the evening, while doing GOTO, the AN said go below the horizon. So the scope stopped when horizontal. I don't know what object Amelia put into the GOTO or thought she put in. So the rest of the night she ran without tracking ( like we did in the old days). Meanwhile, back at Steve's scope, the handpad stopped working. I'm pretty sure its a connection at one of the RJ connectors. I can wiggle a connection point and the HP comes on, sometimes no lights, sometimes a weird set of lights. Its getting cold for us, into the 40's. Remember, we're from the south, not North Dakota. So we called it a night.Amelia logged 2 objects, Steve 1. Steve (going back to stamp collecting) Goldberg On 02/01/2025 3:38 PM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote: Ok ... try the test I had indicated - remove the DSC cable AT the front of the ServoCAT ... see if it then is fully controllable by the handpad.? This is an important test - if the ServoCAT works a bunch of times w/o the DSC cable plugged in.? If it does - and you see this (wrong) action again (note you can do a daytime alignment, doesn't need to be very accurate, just to test this all out so you can possibly fix it BEFORE it gets dark) ... check the GUIDE values on the DSC. Do they seem right? Are they 'going down' as the GOTO slew progresses? Also - try disengaging and seeing if the object is indeed at where you told it to go (of course this would be at night after a real alignment).? You can also go to MODE ENCODER on the AN and see, as the ServoCAT moves, do the encoder values change.? This could be a slipping or non-functional DSC encoder ... if the motor speed seems correct (important distinction) but it seems to take longer to do a GOTO then it might be that the AN is not getting encoder readout partially or at all.? Point the scope straight up (assuming you have that as your ALT REF position) and north. Then turn on, do your FIX ALT REF. Now go to MODE ENCODER, enter. Now move the ALT ONLY down until it matches your LAT. Go to MODE ALIGN STAR, find Polaris, and hit enter. You now have 2/3rd of the alignment done...? open a planetarium program, one that will show stars at the current time and show their current ALT/AZ position. Find one in the sky at that time - go to MODE ENCODER, move the scope to the ALT/AZ position it shows for that star (oh - bright star, so that it is in the BRIGHT STAR catalog)... now go back to ALIGN STAR, enter, find that star - hit enter. You're now aligned. (of course for this you do need the DSC cable plugged in the whole time) ------ Original Message ------ Subject Re: [ServoCAT] Runaway tracking You are making us think back a couple of hours after we have slept. ;) This was the first GOTO of the night. The object was not in the field, too much power eyepiece. Changed to a lower power, then pushed a button to move the scope. She claimed it was moving too fast. So I moved the "speed button" down to the slower speed. She then pushed another button and the scope kept going at the same slower speed, Did the 3-button stop. Pressed a button for 2 seconds or more to reset, and when taking finger off the button the scope kept moving. We did several times. Gary, you asked about the speed of the movement. The speed was the same as the last slew speed? button push. Don't think it was accelerating, we didn't let run that long to see. That is where were stopped for the night. On 02/01/2025 1:19 PM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote: Questions for you... you said Amelia did a GOTO and had no issue... was that the first GOTO or was that later in the session (you mention you were tired indicating possibly it had been working for a while)?? When you say "the scope kept moving, faster than tracking" ... did it appear to accelerate to a stable speed - then continue at a (stable) speed OR did it continue to speed up going much faster than the SLEW rate (rate you'd see when doing a GOTO)?? Try unplugging the DSC cable from the front of the ServoCAT --- then see if the HC can control the scope for slewing. Push the button - does it accelerate up to speed, go at a constant speed as long as you are holding a button, then decelerate to a stop when you let go of the button?? Does it operate in JOG speed the same, only slower overall?? If the motor encoder were not being seen the motor would, due to lack of feedback from its encoder, speed up VERY fast with no perceptible acceleration and it would not stop with a 3 button stop (it MIGHT stop ?- but rarely and only randomly - and it would start up again pretty fast).?
? ?
? ?
|
Gary and Bill, I had a friend make a cable for me. It will be a while before I can test it. My scope is stuffed into our cargo trailer, next to Amelia¡¯s. So for now, lets consider this case closed. Thanks for your help. Steve Goldberg ?
toggle quoted message
Show quoted text
From: [email protected] <[email protected]> On Behalf Of Steve Goldberg via groups.io
Sent: Sunday, February 2, 2025 2:42 PM
To: [email protected]; K9RX - Gary via groups.io <amateurK9RX@...>
Subject: [ServoCAT] Goldberg Hand Pad? I think I figured out my hand paddle control issue.? When I plug the HC into the port on the SC? I can get the motors to spin. Image .2325. If I trace the cable from the SC going to the stalk and plug the HC there, no response from the motors. Image .1357. Last night while trying to figure out the problem,? why jiggle the cable high up the stalk would cause a fault.? Bill, if you think appropriate,? can you send me a new cable? What info do you need from me. Gary, thanks for your help. On 02/02/2025 7:39 AM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote: Good morning Steve and Amelia, Ok ... so mostly good operation last night. A few comments re what you posted: -any 'drift' might be caused by not having done the backlash compensation. Is Amelia's scope and AN set up for the latest versions? If not you might want to upgrade to those as there were significant adds to each of them.? -When you say - and I know its a day later and it looks like you didn't know even then, when you say "go below the horizon"... what does that mean? The AN doesn't actually say that. Do you mean it had an offset for a GOTO that would have taken it below the horizon? With the latest version (and I believe earlier ones) the system would not allow a GOTO below the horizon - the AN would do a down beat - bee...booooooop telling the user that it was indeed an object below the horizon. There is no need to stop using the system at that point - just go to an object that is not below the horizon. Not sure why she gave up. IF you think that indeed as I suggested might be the case for the loooong GOTO's the night before - there might be a slipping DSC encoder, you could at that time (or any time) go to MODE ALT AZ and see if the ALT is indicating it is below the horizon. The AN and ServoCAT have LOTS of protections built in re the horizon. For example if you are tracking an object that sets - the ALT tracking will stop at the horizon (the AZ will continue on). And as mentioned it won't allow a GOTO to an object below the horizon. Further remember that the horizon is as the AN sees it to be from the initial alignment. IF there is a slipping encoder this would of course mess with that potentially. Also - there is a parameter, I believe under SETUP GOTO that allows you to set a local horizon limit. So for example if you have trees all around that limit visibility to no lower than 20¡ã you can program that in. That will then become the local horizon limit. I have mine set to I believe 12¡ã just because I don't want to look through 10+ atmospheres near the horizon nor jeopardize the main mirror moving (tipping).? -re your Gen3 HC. You might want to invest in a spare HC cable. Bill can sell that to you or you can find it online (unknown quality) by looking for a handset cable with a 4 pin RJ22 connector wired as a 'voice' cable.? If it is the connector inside the HC or inside the ServoCAT that would be more work - but that is extremely rare.? You can test the cable by plugging it in (during the day is fine) ... looking at the lights on it. After power up (all lights turn on briefly as a check) it should go to the red GUIDE fast light being on as well as the green GOTO. Wiggle the cable at one end a bunch of times and see if it restarts (lights off and then all lights back on briefly). Repeat at both ends. If one end seems to do this action, and you're sure of it, then reverse the cable and try again at THAT end of the CABLE. So - you have it plugged in and wiggle the HC end. Nothing happens. You wiggle the ServoCAT end and it seems to cause the HC lights to reset... hold THIS end of the cable - unplug it and move it to the HC - THIS end is the suspicious end... plug in the now free end to the CAT. Now repeat by wiggling at the HC. If it does it again then it is indeed the cable. If not - and it does it again by now, again, wiggling at the ServoCAT then its the ServoCAT connection. Contact bill if you suspect it is a fixed connection and not the cable. My strong suspicious is it is the cable.? ------ Original Message ------ Subject Re: [ServoCAT] Runaway tracking Sorry I didn't see this before the evening so couldn't do the test. We did, however, during the day unplug / replug all the data cables, from the 2 motors and the main box. We couldn't do the cable on the AZ motor with the plastic cover. Just could get my hands on it. 1. Last night everything went almost perfect. The tracking wasn't steady, had a slight drift that Amelia could live. NOTHING like we had seen the night before. 2. Later in the evening, while doing GOTO, the AN said go below the horizon. So the scope stopped when horizontal. I don't know what object Amelia put into the GOTO or thought she put in. So the rest of the night she ran without tracking ( like we did in the old days). Meanwhile, back at Steve's scope, the handpad stopped working. I'm pretty sure its a connection at one of the RJ connectors. I can wiggle a connection point and the HP comes on, sometimes no lights, sometimes a weird set of lights. Its getting cold for us, into the 40's. Remember, we're from the south, not North Dakota. So we called it a night.Amelia logged 2 objects, Steve 1. Steve (going back to stamp collecting) Goldberg On 02/01/2025 3:38 PM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote: Ok ... try the test I had indicated - remove the DSC cable AT the front of the ServoCAT ... see if it then is fully controllable by the handpad.? This is an important test - if the ServoCAT works a bunch of times w/o the DSC cable plugged in.? If it does - and you see this (wrong) action again (note you can do a daytime alignment, doesn't need to be very accurate, just to test this all out so you can possibly fix it BEFORE it gets dark) ... check the GUIDE values on the DSC. Do they seem right? Are they 'going down' as the GOTO slew progresses? Also - try disengaging and seeing if the object is indeed at where you told it to go (of course this would be at night after a real alignment).? You can also go to MODE ENCODER on the AN and see, as the ServoCAT moves, do the encoder values change.? This could be a slipping or non-functional DSC encoder ... if the motor speed seems correct (important distinction) but it seems to take longer to do a GOTO then it might be that the AN is not getting encoder readout partially or at all.? Point the scope straight up (assuming you have that as your ALT REF position) and north. Then turn on, do your FIX ALT REF. Now go to MODE ENCODER, enter. Now move the ALT ONLY down until it matches your LAT. Go to MODE ALIGN STAR, find Polaris, and hit enter. You now have 2/3rd of the alignment done...? open a planetarium program, one that will show stars at the current time and show their current ALT/AZ position. Find one in the sky at that time - go to MODE ENCODER, move the scope to the ALT/AZ position it shows for that star (oh - bright star, so that it is in the BRIGHT STAR catalog)... now go back to ALIGN STAR, enter, find that star - hit enter. You're now aligned. (of course for this you do need the DSC cable plugged in the whole time) ------ Original Message ------ Subject Re: [ServoCAT] Runaway tracking You are making us think back a couple of hours after we have slept. ;) This was the first GOTO of the night. The object was not in the field, too much power eyepiece. Changed to a lower power, then pushed a button to move the scope. She claimed it was moving too fast. So I moved the "speed button" down to the slower speed. She then pushed another button and the scope kept going at the same slower speed, Did the 3-button stop. Pressed a button for 2 seconds or more to reset, and when taking finger off the button the scope kept moving. We did several times. Gary, you asked about the speed of the movement. The speed was the same as the last slew speed? button push. Don't think it was accelerating, we didn't let run that long to see. That is where were stopped for the night. On 02/01/2025 1:19 PM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote: Questions for you... you said Amelia did a GOTO and had no issue... was that the first GOTO or was that later in the session (you mention you were tired indicating possibly it had been working for a while)?? When you say "the scope kept moving, faster than tracking" ... did it appear to accelerate to a stable speed - then continue at a (stable) speed OR did it continue to speed up going much faster than the SLEW rate (rate you'd see when doing a GOTO)?? Try unplugging the DSC cable from the front of the ServoCAT --- then see if the HC can control the scope for slewing. Push the button - does it accelerate up to speed, go at a constant speed as long as you are holding a button, then decelerate to a stop when you let go of the button?? Does it operate in JOG speed the same, only slower overall?? If the motor encoder were not being seen the motor would, due to lack of feedback from its encoder, speed up VERY fast with no perceptible acceleration and it would not stop with a 3 button stop (it MIGHT stop ?- but rarely and only randomly - and it would start up again pretty fast).?
? ?
? ?
|
Steve - I'm sending you a private email.
BC
?
|
Gary and Bill,
I think I figured out my hand paddle control issue.?
?
When I plug the HC into the port on the SC? I can get the motors to spin. Image .2325.
?
If I trace the cable from the SC going to the stalk and plug the HC there, no response from the motors. Image .1357.
?
Last night while trying to figure out the problem,? why jiggle the cable high up the stalk would cause a fault.?
?
Bill, if you think appropriate,? can you send me a new cable? What info do you need from me.
?
Gary, thanks for your help.
Steve Goldberg?
toggle quoted message
Show quoted text
On 02/02/2025 7:39 AM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote:
?
?
Good morning Steve and Amelia,
?
Ok ... so mostly good operation last night. A few comments re what you posted:
?
-any 'drift' might be caused by not having done the backlash compensation. Is Amelia's scope and AN set up for the latest versions? If not you might want to upgrade to those as there were significant adds to each of them.?
?
-When you say - and I know its a day later and it looks like you didn't know even then, when you say "go below the horizon"... what does that mean? The AN doesn't actually say that. Do you mean it had an offset for a GOTO that would have taken it below the horizon? With the latest version (and I believe earlier ones) the system would not allow a GOTO below the horizon - the AN would do a down beat - bee...booooooop telling the user that it was indeed an object below the horizon. There is no need to stop using the system at that point - just go to an object that is not below the horizon. Not sure why she gave up. IF you think that indeed as I suggested might be the case for the loooong GOTO's the night before - there might be a slipping DSC encoder, you could at that time (or any time) go to MODE ALT AZ and see if the ALT is indicating it is below the horizon. The AN and ServoCAT have LOTS of protections built in re the horizon. For example if you are tracking an object that sets - the ALT tracking will stop at the horizon (the AZ will continue on). And as mentioned it won't allow a GOTO to an object below the horizon. Further remember that the horizon is as the AN sees it to be from the initial alignment. IF there is a slipping encoder this would of course mess with that potentially. Also - there is a parameter, I believe under SETUP GOTO that allows you to set a local horizon limit. So for example if you have trees all around that limit visibility to no lower than 20¡ã you can program that in. That will then become the local horizon limit. I have mine set to I believe 12¡ã just because I don't want to look through 10+ atmospheres near the horizon nor jeopardize the main mirror moving (tipping).?
?
-re your Gen3 HC. You might want to invest in a spare HC cable. Bill can sell that to you or you can find it online (unknown quality) by looking for a handset cable with a 4 pin RJ22 connector wired as a 'voice' cable.?
?
If it is the connector inside the HC or inside the ServoCAT that would be more work - but that is extremely rare.?
?
You can test the cable by plugging it in (during the day is fine) ... looking at the lights on it. After power up (all lights turn on briefly as a check) it should go to the red GUIDE fast light being on as well as the green GOTO. Wiggle the cable at one end a bunch of times and see if it restarts (lights off and then all lights back on briefly). Repeat at both ends. If one end seems to do this action, and you're sure of it, then reverse the cable and try again at THAT end of the CABLE. So - you have it plugged in and wiggle the HC end. Nothing happens. You wiggle the ServoCAT end and it seems to cause the HC lights to reset... hold THIS end of the cable - unplug it and move it to the HC - THIS end is the suspicious end... plug in the now free end to the CAT. Now repeat by wiggling at the HC. If it does it again then it is indeed the cable. If not - and it does it again by now, again, wiggling at the ServoCAT then its the ServoCAT connection. Contact bill if you suspect it is a fixed connection and not the cable. My strong suspicious is it is the cable.?
?
Gary?
?
?
?
?
------ Original Message ------
Date 2/2/2025 7:21:41 AM
Subject Re: [ServoCAT] Runaway tracking
?
Thanks Gary.
Sorry I didn't see this before the evening so couldn't do the test.
?
We did, however, during the day unplug / replug all the data cables, from the 2 motors and the main box. We couldn't do the cable on the AZ motor with the plastic cover. Just could get my hands on it.
?
1. Last night everything went almost perfect. The tracking wasn't steady, had a slight drift that Amelia could live. NOTHING like we had seen the night before.
?
2. Later in the evening, while doing GOTO, the AN said go below the horizon. So the scope stopped when horizontal. I don't know what object Amelia put into the GOTO or thought she put in. So the rest of the night she ran without tracking ( like we did in the old days).
?
Meanwhile, back at Steve's scope, the handpad stopped working. I'm pretty sure its a connection at one of the RJ connectors. I can wiggle a connection point and the HP comes on, sometimes no lights, sometimes a weird set of lights.
?
Its getting cold for us, into the 40's. Remember, we're from the south, not North Dakota. So we called it a night.Amelia logged 2 objects, Steve 1.
?
Steve (going back to stamp collecting) Goldberg
On 02/01/2025 3:38 PM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote:
?
?
Steve,
?
Ok ... try the test I had indicated - remove the DSC cable AT the front of the ServoCAT ... see if it then is fully controllable by the handpad.?
?
This is an important test - if the ServoCAT works a bunch of times w/o the DSC cable plugged in.?
?
If it does - and you see this (wrong) action again (note you can do a daytime alignment, doesn't need to be very accurate, just to test this all out so you can possibly fix it BEFORE it gets dark) ... check the GUIDE values on the DSC. Do they seem right? Are they 'going down' as the GOTO slew progresses? Also - try disengaging and seeing if the object is indeed at where you told it to go (of course this would be at night after a real alignment).?
?
You can also go to MODE ENCODER on the AN and see, as the ServoCAT moves, do the encoder values change.?
?
This could be a slipping or non-functional DSC encoder ... if the motor speed seems correct (important distinction) but it seems to take longer to do a GOTO then it might be that the AN is not getting encoder readout partially or at all.?
?
Daytime alignment:?
?
Point the scope straight up (assuming you have that as your ALT REF position) and north. Then turn on, do your FIX ALT REF. Now go to MODE ENCODER, enter. Now move the ALT ONLY down until it matches your LAT. Go to MODE ALIGN STAR, find Polaris, and hit enter. You now have 2/3rd of the alignment done...?
?
open a planetarium program, one that will show stars at the current time and show their current ALT/AZ position. Find one in the sky at that time - go to MODE ENCODER, move the scope to the ALT/AZ position it shows for that star (oh - bright star, so that it is in the BRIGHT STAR catalog)... now go back to ALIGN STAR, enter, find that star - hit enter. You're now aligned. (of course for this you do need the DSC cable plugged in the whole time)
?
g.
?
?
?
------ Original Message ------
Date 2/1/2025 4:28:25 PM
Subject Re: [ServoCAT] Runaway tracking
?
Gary and Bill,
You are making us think back a couple of hours after we have slept. ;)
?
This was the first GOTO of the night. The object was not in the field, too much power eyepiece. Changed to a lower power, then pushed a button to move the scope. She claimed it was moving too fast. So I moved the "speed button" down to the slower speed. She then pushed another button and the scope kept going at the same slower speed, Did the 3-button stop. Pressed a button for 2 seconds or more to reset, and when taking finger off the button the scope kept moving. We did several times.
?
Gary, you asked about the speed of the movement. The speed was the same as the last slew speed? button push. Don't think it was accelerating, we didn't let run that long to see.
?
That is where were stopped for the night.
?
Steve & Amelia
On 02/01/2025 1:19 PM CST K9RX - Gary via groups.io <amateurk9rx@...> wrote:
?
?
Hi Steve and Amelia,?
?
Questions for you... you said Amelia did a GOTO and had no issue... was that the first GOTO or was that later in the session (you mention you were tired indicating possibly it had been working for a while)??
?
When you say "the scope kept moving, faster than tracking" ... did it appear to accelerate to a stable speed - then continue at a (stable) speed OR did it continue to speed up going much faster than the SLEW rate (rate you'd see when doing a GOTO)??
?
Try unplugging the DSC cable from the front of the ServoCAT --- then see if the HC can control the scope for slewing. Push the button - does it accelerate up to speed, go at a constant speed as long as you are holding a button, then decelerate to a stop when you let go of the button??
?
Does it operate in JOG speed the same, only slower overall??
?
If the motor encoder were not being seen the motor would, due to lack of feedback from its encoder, speed up VERY fast with no perceptible acceleration and it would not stop with a 3 button stop (it MIGHT stop ?- but rarely and only randomly - and it would start up again pretty fast).?
?
Gary?
?
?
?
?
|
Gabriel Wiklund
