Centering error after plate solve

With two different mounts starting last year with SGP version 3.2.0.613, I have been experiencing a centering error after successful plate solve on the sky on the order of 15 arc minutes off center. The centering process reports success (20px error limit), however the target is ~ 15 arc minutes from the center of the frame to the right or left (probably east or west).

This was not occurring in 2017, 2018 and most of 2019 with my old mount (AP mach1). For a short time I used a Takahashi EM-11, now have new AP mach2. With both of these mounts this error is occurring.

This is after careful polar alignment on a well leveled mount. The first thing I normally do after fine polar alignment is plate solve and sync which nearly always reports success. Then use SGP to slew to a target, then run the centering process based on plate solve. This used to work beautifully with the mach1. Starting with the EM11, then later with the mach2, this has consistently resulted with an offset. I just don’t see how a plate solve based centering can result in the target 1/3 of the frame off the center and report success. The clock time is accurate on my controlling laptop and the mount is synced to that time. If anybody on this forum has experienced this I would like to hear what may have worked to correct this frustrating behavior.

Note, prior to ver: 3.2.0.613, I had 3.0.3.169, then 3.1.0.322 beta.
3.2.0.613 was installed around 10/13/2020. This issue started prior to that date and continued with 3.2.0.613 install.

thanks

This would happen if the target coordinates you gave SGP are off by that amount.

Kind regards,
Horia

Hi,

I have experienced this only when I forgot to enter year 2000 epoch coorditates for the target. SGpro expects this as you probably know. Can this be the case ?

CS,
Janos

Yes, however it occurs with any target attempted. Coordinates used from various sources.

Thank you for responding, I have thought about that and checked a few targets for the difference between J 2000 and J now and the difference was only a few arc minutes as large as the error being produced, nearly 15 or minutes.

I will be careful and check again next time out.

Thank you for responding, checking the difference in coordinates between J2000 and Jnow for Capella for example, it was 2 arc min in RA and DEC. That would not account for the roughly 9 arcmin offset experienced.

Can you remember how much pointing error resulted in your experience?

thanks,
Steve

As far as I can recall it was between 5-10 arcmin. But results will vary dependent on the epoch of your source data and the expected pointing accuracy you have entered in SGpro,

CS,
Janos

Check the time you are using, if your using DST or that setting wrong you might get pointing errors. My hand ox will do that, and when I imaged over the transition fro dst the time updated in my computer but not my telescope or SGP.

Thanks for responding. I thought about that. If off by an hour, the error would be 15 deg would it not? The target would be nowhere near the camera frame. The target is in the frame when I do the fine centering with plate solve. The issue is a roughly 9 arc min offset from the center with SGP reporting success (within the 20 pixel limit I set).