PrecisePointing issues

Hello,

my astrophotography setup shows severe pointing problems several times during an imaging night. The problem seems not to be missing precision, but sometimes missing or strange movement of the mount.

The Voyager log of last night counts 56 precision pointing operations (due to slewing to different targets or refocus operations). 20 of these succeeded with the initial movement, 23 after 1 retry and 1 after 3 retries. But 12 operations failed even after 3 retries with “Error out of range”. Of course, my setup of 25” error limit might be too low for the HEQ5 mount, but two observations seem to indicate another problem: The pointing error was even after the 3rd retry still above 10’ (not " - no typo) several times and it seems like in these cases the error seems not to improve from one retry to the next retry.

If you look at this partial extract of the Voyager log:

[PrecisePointing] - [SYNC_MOUNT_Code ] - Solved (J2000) coord converted to (JNow) RA=11 19 29,566 DEC=13 07 50,03
[PrecisePointing] - [SYNC_MOUNT_Code ] - Telescope Coord Before Sync => (JNow) RA=11 19 29,458 DEC=13 07 56,28
[PrecisePointing] - [SYNC_MOUNT_Code ] - Begin Sync
[PrecisePointing] - [SYNC_MOUNT_Code ] - Mount Sync on (JNow) RA=11 19 29,566 DEC=13 07 50,03
[PrecisePointing] - [SYNC_MOUNT_Code ] - Telescope Coord After Sync (JNow) => RA=11 19 29,567 DEC=13 07 49,96
[PrecisePointing] - [SYNC_MOUNT_Code ] - Target Coord (JNow) => RA=11 20 50,121 DEC=13 10 12,03
[PrecisePointing] - [CHECK_POINTING_ERROR_Code ] - Pointing Error Spherical => 00 19 45,08
[PrecisePointing] - [CHECK_POINTING_ERROR_Code ] - Error out of range [Max 00 00 25,000 ], retry another time [3]
[TelescopeGoto ] - [CHECK_TELESCOPE_CONNECTION_Code] - Actual Position (JNow) (RA=11 19 29,573 / DEC=13 07 49,96 )
[TelescopeGoto ] - [RUN_ASYNC_Code ] - Slewing Async (JNow) RA=11 20 50,121 DEC=13 10 12,03 …
[TelescopeGoto ] - [FINISH_Code ] - Actual Position (JNow) (RA=11 19 30,032 / DEC=13 07 50,68 )
[PrecisePointing] - [SYNC_MOUNT_Code ] - Solved (J2000) coord converted to (JNow) RA=11 19 29,566 DEC=13 07 51,36
[PrecisePointing] - [SYNC_MOUNT_Code ] - Telescope Coord Before Sync => (JNow) RA=11 19 30,037 DEC=13 07 50,68
[PrecisePointing] - [SYNC_MOUNT_Code ] - Begin Sync
[PrecisePointing] - [SYNC_MOUNT_Code ] - Mount Sync on (JNow) RA=11 19 29,566 DEC=13 07 51,36
[PrecisePointing] - [SYNC_MOUNT_Code ] - Telescope Coord After Sync (JNow) => RA=11 19 29,581 DEC=13 07 51,40
[PrecisePointing] - [SYNC_MOUNT_Code ] - Target Coord (JNow) => RA=11 20 50,121 DEC=13 10 12,03
[PrecisePointing] - [CHECK_POINTING_ERROR_Code ] - Pointing Error Spherical => 00 19 45,14
[PrecisePointing] - [CHECK_POINTING_ERROR_Code ] - Max retry reached

I wonder especially what the line “[TelescopeGoto ] - [FINISH_Code …” means. The “Slewing Async” command one line above issues a slew to the correct target position, but the mount reports a wrong position at the end of the slew (even before solving)?

My setup: HEQ5 mount with EQDirect/EQmod, ASCOM, Voyager 2.2.16

Does anyone have discovered similar problems or any idea how I can fix the problem? I do not care about a small error, but sometimes the frame displacement is way to large to stack frames captured after a pointing operation with the frames captured before.

Clear skies,
Joachim

Joachim, Voyager is a multithread system and a order of log for some lines is something you cannot understand without know code. Try to start to check from the mount : improve balancing, check backlash, check your cable routing, verify you dont have passing the weight allowed , verify the coupling of gear, and so …

All the best
Leonardo

Hello Leonardo,
thank you for your very fast reply! I will try to check mount behavior and to log the communication with the mount, especially the sync commands.

While evaluating the issue, I found an unexpected behavior: When a sequence is interrupted by a Voyager Robostar focus operation, after return from the focus star there is a precise pointing operation to restore the previous pointing. If this precise pointing fails after the third unsuccessful retry, there is no error thrown and imaging continues with the camera pointing to the wrong (out of limits) position. Shouldn’t the sequence be aborted with an error in this case?

Best regards and thank you for your support,
Joachim

Hi Joachim,

Voyager work in this way, when a restore from focus fails an emergency fastback goto will be done to continue sequence. If you want to stop the problem at the beginning doesn’t allow the 4th retry on pointing in setting, in this case, when at beginning your mount cannot point the target the sequence will be aborted.

As I wrote previously, the behavior of your mount is not normal. Fix the mount issues and you will see that it won’t take much to aim the target correctly. I don’t want you to think the problem is Voyager.

All the best
Leonardo

Hi Leonardo,

first of all: I really don’t think the problem is Voyager! I really like your software and rely on it.

One of the features of Voyager I like especially is the very detailed log file and in case of my current pointing issue I use it as a source of information about what has happened.

I would like to stop as soon as the problem occurs and abort before the 4th retry on pointing - like you have described. How / Where can I configure this? I found in “Setup/Mount” the option “Use the best performance after finished pointing retries”, but this was already not enabled in my setup. Is there another place to disable the 4th pointing retry?

Best regards and thank you for your support,
Joachim

Is there any consistent area of the sky where this is occurring? Particularly near the meridian.

I had an issue with my Atlas Pro (AZEQ6 clone) which would cause pointing to fail after meridian flips, cone error in the setup would result inactual pointing of the telescope being on the opposite side of the meridian to where it was supposed to be (Just, only a couple of arc minutes) EQMOD would reject the sync due to the plate solve being on the wrong side of the meridian and then Voyager would continue as best it could. Nothing to do with Voyager, which coped with it far better than other software I have used, which would just stop the sequence in its tracks. If I ticked the option to periodically re-center, Voyager would have re pointed itself properly automatically after a period, though that is intended to make sure unguided dithering does not put the target too far off center rather than fix issues like my mounts.

If it is happening after flips, that would be one thing to check. Fixed in my case by delaying the flip to further past the meridian to ensure that the initial goto would reliably fall to the west of the meridian when all errors were taken in to account.

Hello Blue,

thank you for this hint. I have already considered problems with EQMOD and syncing to the pointing model and I am still investigating this.

At least during the last imaging session the problems occurred definitely not near the meridian but I’ll try the resync workaround.

Thank you for your help,
Joachim

Another thing has occurred to me, in EQMOD have you got it’s behavior set to “Append on Sync” or “Dialog” mode? Append on sync (Building a pointing model) gave me trouble early on when I first started imaging (With different software) and the mount would sometimes seem to have a mind of it’s own when doing precise pointing. The next software I used suggested dialog mode and I have never had it make that sort of unexpected move since.

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Thank you, that is a very good hint! My setting was “Append on Sync”,I will try the Dialog mode as soon as the sky is clear again.