Re: Bad images _Bouncing stars


Mike Shade
 

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:

mshadephotography.com

 

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: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of John Thompson via groups.io
Sent: Friday, May 01, 2020 4:51 PM
To: main@ap-gto.groups.io
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.

Thanks for your responses.   

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