Mount acting wierd

[Rodd]

I use a Mach q GTO mount and have been very pleased with it.  It suddenly began acting in a manner that makes no sense.  I am currently using a C11Edge at F10 (FL or 2,800 mm).  Up until recently I could take 30 sec unguided subs very successfully.  Lately, I will center a bright star and leave it there with the mount tracking for 30 minutes.  After 30 minutes I take a sub and the star has drifted a very small amount.  Everything looks great.  However, when I begin taking 30 sec subs, the drift increases to an amount where you can see the star move after each 30 sec sub.  After 30 minutes its 1/4 way across the FOV.   I use Maxim DL  for acquisition.  This behavior makes no sense.  the mount is on its own power supply and the camera is on another power supply--so power has noting to do with it.  Does anyone have any ideas?  I am trying to ask AP but am getting few remarks and they are days apart and are not helping at all.  Polar alignment is as good as I can make it--it has always been good enough.  I leave my scope setup and PA does not change.  A month will go by and Polaris is exactly where it should be.  I check  it before every session, but most nights I do not have to change it.

Regardless of the what the problem is...e.g. a cable issue, moisture in the controls, a short, a Maxim DL setting, etc, why would drift change when I am imaging.  the mount is tracking precisely the same whether I am imaging or not.  It makes no sense.  The light is on on the mount, so it has power.  It parks well, slews manually well.   Please, if anyone has any ideas I would be most grateful.  this is ruining my imaging sessions and there is no end in site.  Will the problem go away if I guide?  I have to install an OAG to guide and have not had any clear sky time.  When I do get a few hours I do not want to waste it screwing around trying to get the OAG to work.

Thanks,

Rodd

[almcl]

When I experienced this problem it was down to differential flexure.  Never did establish exactly where this was occurring - could have been mirror flop, focuser sag on the guide scope, something else entirely or a combination of all three. 

As to why yours manifests only when imaging, that is a puzzle.

Mine was cured when I moved from a guide scope to an OAG but I was already guiding (only on a Skywatcher EQ5 to which I had added stepper motors) so can't promise that guiding without an OAG will cure it but there's a good chance an OAG will make a difference.

[Shibby]

I know this is a super-late reply! Just curious, really, if you resolved your problem @Rodd? I have the same mount and have not encountered this issue. I do have a small amount of drift, probably due to flexure, but nothing problematic. It almost sounds as if it was tracking at lunar rate rather than sidereal.

You mentioned polaris with regards to your polar alignment, so I assume you're using the polar scope? I suggest doing a drift alignment if you want the best result for imaging. Like you, I have mine permanently mounted but always do a few fresh drift aligns each season.

Communication/power issues: If you use ASCOM, you can check the number of signal transmission errors in AP's ASCOM driver. Although, if you're not guiding then there's probably not that many signals being sent to the mount. I once had an issue with my power cable and found that the ASCOM driver actually crashes and locks up completely when the mount loses power.

[Rodd]

3 hours ago, Shibby said:

I know this is a super-late reply! Just curious, really, if you resolved your problem @Rodd? I have the same mount and have not encountered this issue. I do have a small amount of drift, probably due to flexure, but nothing problematic. It almost sounds as if it was tracking at lunar rate rather than sidereal.

You mentioned polaris with regards to your polar alignment, so I assume you're using the polar scope? I suggest doing a drift alignment if you want the best result for imaging. Like you, I have mine permanently mounted but always do a few fresh drift aligns each season.

Communication/power issues: If you use ASCOM, you can check the number of signal transmission errors in AP's ASCOM driver. Although, if you're not guiding then there's probably not that many signals being sent to the mount. I once had an issue with my power cable and found that the ASCOM driver actually crashes and locks up completely when the mount loses power.

Thanks for responding. Whatever the problem was, it no longer matters. I started guiding again.  All is well now.  I never did figure it out. I got an OAG so I could guide.  That was inevitable, I guess.  CS!