Guiding Issues? Flexure?

[04Stefan07]

Just going over my data I captured over 5 nights of the Rosette Nebula and have noticed some star issues between subs. See main setup in my signature (GT81).

After dialing in my back focus and tilt (finally) these are at a minimum. I have less than 6% tilt and I think my back focus is almost bang on.

I have attached some subs which were taken one after another and wanted to get some opinions on what my issue could be.

My guiding is generally alright (around 0.4 - 0.6 RMS depending on the night) but I have noticed every now and then my DEC on PHD2 goes nuts then corrects itself. I think I may have some backlash in the mount.

Also in my final stacked images which are 2x drizzled the stars look alright but I wouldn't mind trying to fix this.

The image attached I have circled some reference stars and you can see they become slighly elongated.

[SamAndrew]

are all the stars the same? a full frame sub might help.

Edited February 22, 2023 by SamAndrew

[michael8554]

Hi Stefan

"My guiding is generally alright (around 0.4 - 0.6 RMS "

But are RA and Dec figures similar, and smaller than your pixel scale ?

If not you may have elongated stars.

Do the subs with elongation correspond to when "DEC on PHD2 goes nuts" ?

You could post the PHD2 GuideLog.

Michael

[newbie alert]

On 21/02/2023 at 15:38, 04Stefan07 said:

Just going over my data I captured over 5 nights of the Rosette Nebula and have noticed some star issues between subs. See main setup in my signature (GT81).

After dialing in my back focus and tilt (finally) these are at a minimum. I have less than 6% tilt and I think my back focus is almost bang on.

I have attached some subs which were taken one after another and wanted to get some opinions on what my issue could be.

My guiding is generally alright (around 0.4 - 0.6 RMS depending on the night) but I have noticed every now and then my DEC on PHD2 goes nuts then corrects itself. I think I may have some backlash in the mount.

Also in my final stacked images which are 2x drizzled the stars look alright but I wouldn't mind trying to fix this.

The image attached I have circled some reference stars and you can see they become slighly elongated.

So from left to right.. first is to the middle left of the image and the rest are top left?

How does the rest of the stars in the image look as from what you have looks confusing..

If it's drift it would usually be on one particular axis so stretched stars in 1 direction, if it's spacing it would show stretched stars pointing inwards if it's too close and going around the circumference if it's too far( you seem to have both)...

With my William optics ed80 I thought I had tilt but it showed to be focuser tube sag as one of the bearings eventually gave up... William optics were just useless, blatantly said the focuser is no longer used, we don't have spares, can't help... ( Turned out to be a simple fix)

So that's the last William optics scope that I buy