Guide star kept drifting...

[Forum_2015]

Hi there,
Last night when I try guiding through AA5 I experienced something interesting - the guide star I marked drifted out of the frame after about 20 seconds when guiding actually started, i.e. after calibration and after I hit the 'Mark star' button. Apparently AA5 tried to move the star back, but just couldn't.
It may seem to be a scope connection problem but the strange thing is, it happened *after* the calibration, since AA5 calibrated just fine(no complaints) so the scope connection must be good , isn't it?

No matter what I tried (restart AA5, park scope and reconnect, etc.), this problem persisted for about 20 minutes and magically went away - guiding is performed as expected... my scope didn't cross meridian for the time being, it was on the same side. I continued my imaging session for about 4 hours since after, and the guiding was like flawless...

I know my polar alignment was good enough since I did 3 iterations using AlignMaster. Guide camera is Lodestar X2 (AA5 driver DLL) and scope connection is ASCOM/EQMOD. Windows XP 32-bit.

Anyone had similar issue before? Could this be just some kind of software glitch, or physical like how my scope was balanced?

Thanks,
Yue

[Forum_2015]

Hi,
during those 20 minutes, were you able to calibrate again? The result of the calibration was almost the same?

[Forum_2015]

I thought I was able to calibrate during that 20 minutes and the star kept drifting.
However, last night I noticed another strange behavior right after activated the guiding - i'm not sure how to describe it properly but the guide star was 'circling' around the big green cross hair. In about 20-30 minutes I was able to re-calibrated a few times but couldn't get rid of the 'circling' movement - it happens after I hit 'Mark Star' ; then again it went back to normal and the guiding was again almost perfect for about 2 hours till the end of my imaging session.
I noticed when this happens my scope was very close to meridian - maybe I just shouldn't pick a star near meridian to calibrate?

Yue

[Forum_2015]

Maybe backlash in RA? Because the scope was in position where it starts "pulling" in RA instead of "pushing"? I admit that this is unlikely, but you could verify the clutch and/or balancing better the scope. By the way, note somewhere the "correct" calibration (speed X and Y) and verify that they don't change too much on different nights.

[Forum_2015]

Thanks Fabio. Yeah, it could be the backlash. I'll keep my eye on the calibration settings.
Also I think I can pick a star that not close to meridian, calibrate the guiding, then slew to the actual object I want to imaging without re-calibrating - if it's on the same side of meridian.