PHD2 Dec tracking goes runaway after Meridian Flip with Mach1

John Davis

I'm sure this is a configuration problem, but I have not been able to find a clear answer searching the web, so I thought I'd post here to get input from the AP experts.

I have a new-to-me Mach1 that I have had out now for 4 sessions totalling about 20 hours of imaging.  I have been working the Bubble nebula, so I start out early in the evening when it is east of the meridian, and then later it crosses to west of the meridian.

The mount guides great from starting time until it is time for meridian flip.  After the meridian flip, it guides fine for anywhere from a few seconds to a minute - until there is the first commanded correction in Dec.  Then the Dec corrections continue and get larger - driving the scope off of the guide star until PHD2 loses it.  See attached screen shot from the PHD2 log viewer (post_meridian_flip_guiding_1.png

In PHD2 I have the box checked that says "Reverse Dec output after Meridian flip"  - because I thought I read on posts here (and in the doc maybe) that it needed to be set.  But even after un-checking that box, it continues to misbehave.

I have stopped PHD2 and re-calibrated -  using a star on the same side of the meridian and near the C-equator with mixed results.  On Saturday night, I parked the scope, turned off the mount, turned it back on, then re-calibrated PHD2  on a star west of the meridian and slewed back to the Bubble nebula west of the meridian.  Then PHD2 and the mount tracked fine.  Re-initializing the mount may not be necessary - I was not as much in troubleshooting mode as I was in "get back to imaging" mode - so I didn't do a very controlled experiment.

I don't know if it is pertinent or not, but I have the AP ASCOM driver set to allow the scope to go 60 minutes (-1 hours in the field of the driver dialog) past the meridian, and I have SGP configured to delay issuing the slew causing the flip until 60 minutes after crossing the meridian.   There is plenty of clearance with the scope and tripod/mount for that, so I was delaying the flip because I have been fighting getting it to work.

I've added the PHD2 log file as well - but I have posted the same question to the PHD2 discussion group.
I wanted to make sure there was not any AP specific configuration that I was missing.

Any help would be greatly appreciated.  Thanks!
John D.

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