Re: Bad images _Bouncing stars
Good to see feedback. Not sure what your mount/imaging system is but a good test might be to see what the mount does unguided for a worm cycle...with PEC on and PEC off (you have a good PEC curve right?). My 1600 it is a 382" period. Asking a mount to go unguided for 20 minutes (1200 seconds), unless you have a very low resolution system is asking a lot and you will likely get some RA drift, or other errors (mirror flop, component sag, dragging cables, and optical aberrations caused by seeing variations to name a few) and this is not unexpected. See what it does for a worm cycle.
Mike J. Shade
Mike J. Shade Photography:
In War: Resolution
In Defeat: Defiance
In Victory: Magnanimity
In Peace: Goodwill
Sir Winston Churchill
Already, in the gathering dusk, a few of the stars are turning on their lights.
Vega, the brightest one, is now dropping towards the west. Can it be half
a year since I watched her April rising in the east? Low in the southwest
Antares blinks a sad farwell to fall...
Leslie Peltier, Starlight Nights
International Dark Sky Association: www.darksky.org
From: firstname.lastname@example.org [mailto:email@example.com] On Behalf Of John Thompson via groups.io
Sent: Friday, May 01, 2020 4:51 PM
Subject: Re: [ap-gto] Bad images _Bouncing stars
This is a follow up to my "Bouncing Stars" post. I
imaged the next night (with and without guiding) for 1200 sec exposures. The
images were fine (round stars) no zig-zag patterns or elongated stars. I did
notice a slight oblong effect in the unguided image. Looking at PHD2
graphics it appears I have some drift in RA that I must correct. All my RA
corrections were on the same side of the graph.I believe that signifies an RA
drift ? Looking at my PHD2 log from night one I see a frequent occurrence of
"guide star lost" either for low SNR or low Star mass. I assume that
losing the guide star for long periods means large sudden corrections and the
"bouncing" I described. In any case I am attributing the primary
cause of the problem to the guiding software either due to a settings error or
poor selection of guide star. I will work on a solution with PHD2. Definitely
not a mount problem as proved by last nights test. If anyone has a proven set
of PHD2 settings i would appreciate getting them.