Losmandy Gemini - Which mount startup procedure to best maintain pointing?

Hi All,

I have a question about ACP's pointing correction which eventually is causing my scope to point in the wrong direction e.g. not centering the target accurately after the system has been used for a few sessions. However, this is not an ACP problem but I believe this happens when the mount powers up again and is not pointing where ACP thinks it is e.g. could have been moved a bit. I then imagine this slight random offset gets built 'into' the pointing model over time as ACP learns and eventually causes pointing to deteriorate, because when I clear the pointing model in ACP preferences it can center targets perfectly again.
So I'm sure this is not an ACP issue as such, but more a question of how to use my mount correctly together with ACP.

I am using a Losmandy mount with the Gemini II controller and what I do is to normally park the scope in CWD position after a session. Now if things were perfect I could just always do a 'warm restart' - which for Gemini means the mount powers up using the last RA/Dec coordinates and all should be good. This is also the suggestion from other similar threads here.
But in reality sometimes there will be an issue which require me to 'cold start' the mount, and in this case Gemini always assumes it starts in CWD position. But I don't know the exact CWD position, other than eye-balling it. Same applies if I say took the camera on and off, or accidentally bumped the scope - it will not point precisely where it was left last time.

So what is the best startup procedure here? How do I sync the mount back so ACP can continue building the pointing model session after session? Should I simply use the 'recover lost scope' script every time I start?

Regards,
Rolf

Rolf -- In theory, ACP will do a SYNC to the mount for the first pointing update for the night. This is supposed to remove any fixed bias that may change from night to night (imperfect parking etc). But ACP knows nothing about the internals of the scope controller. Are you using EQMOD to control the Gemini? If so I recommend the pointing corrector built into the EQMOD.

Thanks Bob, that makes sense. And I am using the Gemini .Net ASCOM controller, latest version, for controlling my Losmandy G-11 mount.

What happens to the model if the plate solution is successful but perhaps incorrect e.g. say stars in the pointing image were trailed or there were clouds so that the point sources extracted from the image may not be reliable, but plate solving still returns a result which is then used for the pointing model? This has happened to me several times. Could that cause the model to deteriorate?

Yes false PinPoint solutions could degrade the model. Please save your model (ACP Telescope menu, Save Model As...) then zip it and attach it to a reply <- link to attaching instructions. I'll analyze it here and let you know how it looks.

Thanks Bob, I'll do that next time I see the problem.