Help with Diagnosis of Odd Guidance problem with iOptron ZEQ25 Mount/PHD2
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billbinmontana
Jul 12, 2016, 5:44:01 PM7/12/16
to Open PHD Guiding
Hi everyone:
I have an iOptron ZEQ 25 mount, which I have had for since the fall of last year. The mount is on a permanent pier and has been leveled and polar aligned using a QHY Polemaster.
Up until just recently, the mount has performed admirably well - tracking very nicely when autoguided using a QHY 5-II camera with an Orion Guidescope and PHD2. My primary imaging telescope is a
Takahashi Epsilon E-130D. The primary imaging camera is a cooled Canon 600D DSLR. The scope with camera, guidescope, etc. are carefully balanced in both RA and DEC before each imaging session.
On the night of July 5th, I was able to get a superb set of subframes of the Andromeda Galaxy with the setup performing at its very best. The following evening, all hell broke loose (typical for this hobby).
The guiding and tracking was horrible. In PHD2, the tracks for both the RA & DEC were below the zero line and both following exactly the same tracks, which was very odd. The individual tracks across the target
were at a 45 degree angle to the northwest, which was also very odd. What was also odd - I made no changes in any of the settings from night to night. Attached is a screen shot of PHD2 that shows this very odd tracking
behavior that I have tried to describe verbally.
Last night I tried another imaging session of the Bubble Nebula (NGC 7635) region and the same thing happened. So, I decided to do a star-cross test to hopefully try to determine the root cause of this problem. According to
the recommended test procedure I set the tracking rate of the mount at 1x sidereal. I then opened the "Manual Guide" tool in PHD2 and set the pulse size at 5 seconds and proceeded to perform the test while
capturing a 60 second image of the target star field with the Canon DSLR.
Attached is an image of the star-cross test results along with another image of the same star field that was a single unguided 60 second exposure (unprocessed) so you can see where I was in the sky. In both images, North is roughly vertical (up).
As you can see from the star-cross test, the mount appears to only show responses to the manual guide in the east-west direction while the north-south direction shows no responses other than trailing over a 60 second test period.
I repeated the test several times with exactly the same results.
I have also attached the Guide Log and Debug Log for the evening. The latter portions of these logs will reflect the logs of the star-cross test, while the earlier segments will reflect the odd tracking behavior during PHD2 guiding.
You can use the time stamps in the logs to coordinate the actions with times reflected on the screen shot, etc.
So, after reviewing the information, what do you experts out there think is the root cause of the problem? Have you seen this before?
Based on the star-cross test, it would appear that it is not a PHD2 guidance problem, nor a problem with the guide camera. My best guess is that there may be a problem with the RA board in the mount as the guide port is a part of
that board - but that is only a guess.
Looking for expert help to diagnose the problem with an aim to a final solution. Thanks in advance for looking into this and letting me know what is going on here.
Bill B in Montana
I have an iOptron ZEQ 25 mount, which I have had for since the fall of last year. The mount is on a permanent pier and has been leveled and polar aligned using a QHY Polemaster.
Up until just recently, the mount has performed admirably well - tracking very nicely when autoguided using a QHY 5-II camera with an Orion Guidescope and PHD2. My primary imaging telescope is a
Takahashi Epsilon E-130D. The primary imaging camera is a cooled Canon 600D DSLR. The scope with camera, guidescope, etc. are carefully balanced in both RA and DEC before each imaging session.
On the night of July 5th, I was able to get a superb set of subframes of the Andromeda Galaxy with the setup performing at its very best. The following evening, all hell broke loose (typical for this hobby).
The guiding and tracking was horrible. In PHD2, the tracks for both the RA & DEC were below the zero line and both following exactly the same tracks, which was very odd. The individual tracks across the target
were at a 45 degree angle to the northwest, which was also very odd. What was also odd - I made no changes in any of the settings from night to night. Attached is a screen shot of PHD2 that shows this very odd tracking
behavior that I have tried to describe verbally.
Last night I tried another imaging session of the Bubble Nebula (NGC 7635) region and the same thing happened. So, I decided to do a star-cross test to hopefully try to determine the root cause of this problem. According to
the recommended test procedure I set the tracking rate of the mount at 1x sidereal. I then opened the "Manual Guide" tool in PHD2 and set the pulse size at 5 seconds and proceeded to perform the test while
capturing a 60 second image of the target star field with the Canon DSLR.
Attached is an image of the star-cross test results along with another image of the same star field that was a single unguided 60 second exposure (unprocessed) so you can see where I was in the sky. In both images, North is roughly vertical (up).
As you can see from the star-cross test, the mount appears to only show responses to the manual guide in the east-west direction while the north-south direction shows no responses other than trailing over a 60 second test period.
I repeated the test several times with exactly the same results.
I have also attached the Guide Log and Debug Log for the evening. The latter portions of these logs will reflect the logs of the star-cross test, while the earlier segments will reflect the odd tracking behavior during PHD2 guiding.
You can use the time stamps in the logs to coordinate the actions with times reflected on the screen shot, etc.
So, after reviewing the information, what do you experts out there think is the root cause of the problem? Have you seen this before?
Based on the star-cross test, it would appear that it is not a PHD2 guidance problem, nor a problem with the guide camera. My best guess is that there may be a problem with the RA board in the mount as the guide port is a part of
that board - but that is only a guess.
Looking for expert help to diagnose the problem with an aim to a final solution. Thanks in advance for looking into this and letting me know what is going on here.
Bill B in Montana
bw_msgboard
Jul 12, 2016, 6:23:40 PM7/12/16
to billbinmontana, Open PHD Guiding
Hi Bill, sorry you’ve run into problems. There seem to be lot of things wrong here so I think it would be better to get back to basics and better understand what your mount is doing. You’re running an old release of PHD2 that doesn’t have a lot of the analysis and logging tools that can help sort these things out. Here’s what I recommend:
- Upgrade to the 2.6.1 PHD2 release or even better, to the latest dev release available here: http://openphdguiding.org/development-snapshots/. Don’t un-install anything, just run the installer for the posted release.
- Use the new-profile-wizard to create a new profile for your configuration, keeping the same settings you have for camera, mount, focal length, pixel-size, etc. This will establish a good baseline for guider settings. Some of the ones you have now – for example RA min-move – look awful. Give the profile a new name and use that profile going forward.
- Build and use a dark library for the new profile – you aren’t using one currently, which is not recommended.
- Start using guide cam exposure settings of 2-3 seconds, letting PHD2 auto-select a good guide star.
- Run a new calibration, noting any calibration alerts that may show up. Your star-cross test suggests you have a large amount of dec backlash, so that may cause some difficulty with calibration. If so, review the help docs regarding calibration problems and how to work around them.
- After getting a good calibration, run the Guiding Assistant, letting it run for 4-5 minutes before then allowing the backlash measurement process to run.
When that’s all done, send us both your guide and debug log files and we’ll see what’s going on. Some of this may sound new to you, so it would probably be worth spending some time to read the help doc that is part of the latest release. While this all may sound like too much work, it’s more likely to lead to a good diagnosis of your problems and how best to fix them. Trying to unravel things one perceived problem at a time could take forever.
Good luck,
Bruce
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