Poor Guiding Immediately After Meridian Flip – EQ6-R Pro + EdgeHD 8 + OAG

[Mupanga Mwanakatwe]

Hi everyone,

I am looking for some help diagnosing a guiding problem that only occurs after a meridian flip.

Equipment

• Mount: Sky-Watcher EQ6-R Pro
• Telescope: Celestron EdgeHD 8
• Guide scope: Off-Axis Guider (OAG)
• Guide camera: ZWO ASI174MM Mini
• Imaging camera: ZWO ASI533MM Pro
• Imaging software: NINA
• Guiding software: PHD2

Problem
Guiding is generally very good before the meridian flip. However, immediately after the meridian flip, the guiding deteriorates significantly and remains poor for the rest of the night.

The calibration appears to complete successfully, but the guiding RMS increases substantially after the flip.

Things I have already checked

• Polar alignment is good.
• Guiding before the flip is consistently good.
• I use an OAG, so guide scope flexure should not be the issue.
• I have checked the PHD2 calibration and it appears reasonable.
• There is currently no autofocus run after the meridian flip.
• The EdgeHD mirror is focused using a ZWO EAF.

I have uploaded the PHD2 guide and debug logs here:

[Paste your PHD2 log upload link here]

Could someone please review the logs and advise what might be causing the poor guiding after the meridian flip? In particular, I would appreciate any comments on:

• Calibration quality.
• Whether there are signs of mount backlash or stiction.
• Any indication of cable drag or mechanical issues.
• Whether there are PHD2 settings that should be changed.
• Any evidence suggesting mirror movement or another mechanical cause.

Log Files Link: https://openphdguiding.org/logs/dl/PHD2_logs_4QzN.zip

Thank you for your time and any suggestions.

[Brian Valente]

Hi Mupanga

The main issue is you need to change your setting for reverse dec after flip. (see screen capture below). That should resolve the issue.

Other feedback:

- the second calibration looks okay.but you should calibrate using the calibration assistant at declination = 0 (or as close to it as possible)

- your polar alignment should be improved, all your Dec pulses are in one direction. The best way to measure this is do a Guiding Assistant run immediately following  your calibration

- 5 second exposures is probably too long for your mount. I suggest you target the 2-3 second exposure time if you can pull it off with the oag/sct.

- your RA residual error is still quite high for your primary period (0.8") - suggest you enable PPEC algorithm with the period at 474 second and auto adjust disabled

Brian

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Brian Valente

astronomy portfolio https://www.astrobin.com/users/bvalente/ 

[Bruce Waddington]

Also, your guide camera is running in 16-bit mode which is good, but you've set your SaturationADU value to 255 which is only appropriate for 8-bit cameras.  This means that most of your guide stars are judged as being saturated and you aren't able to use some of the best available guide stars.  On the Camera tab of Advanced Settings, set the Saturation by Max-ADU value to 65500.

Regards,

Bruce