First stack from different software looks weird.

[upahill]

A bit out of practice, but the having switched to INDI/Kstars etc I managed to get a few subs last night for the first time, I have stacked them using basic DSS settings and im getting what looks like field rotation/radial banding in the final image. Haven't come across this before and the rotation does appear to be centres on the image itself.

Any ideas what causes this, each individual sub looks ok but there were no calibration subs on this, my only thought so far is that maybe the camera was slipping in the focuser during the night but doesnt seem likely. Hopefully the attached screenshot is large enough to see the effect.

 

[vlaiv]

Image seems to be stacked ok - but yes, there is walking noise that is not "walking properly".

Can you inspect individual frames and see what sort of movement between frames you are getting (follow particular star or set of stars and see how they move). Another option that can help diagnose is to stack subs without aligning them - you should get a sort of "star trails" - depicting how your mount moved or dithered.

If you are guiding (which is most likely in order to get this sort of thing) - problem could be poor polar alignment. Maybe could be due to orthogonality error, but I'm not sure about that.

If you are not guiding - then maybe some sort of weird cable snag or mount friction that is reducing motion in one direction.

[upahill]

40 minutes ago, vlaiv said:

Image seems to be stacked ok - but yes, there is walking noise that is not "walking properly".

Can you inspect individual frames and see what sort of movement between frames you are getting (follow particular star or set of stars and see how they move). Another option that can help diagnose is to stack subs without aligning them - you should get a sort of "star trails" - depicting how your mount moved or dithered.

If you are guiding (which is most likely in order to get this sort of thing) - problem could be poor polar alignment. Maybe could be due to orthogonality error, but I'm not sure about that.

If you are not guiding - then maybe some sort of weird cable snag or mount friction that is reducing motion in one direction.

Im guiding, but getting used to the new guiding process in EKOS - I was using PHD before and it was simple, this seems a little trickier.

Ill have to examine the individual subs a little more closely I think as you said.

[alacant]

19 hours ago, upahill said:

- I was using PHD before

Hi. Use it with EKOS as well? It's much more refined than the internal guider.

Cheers

[-Joe_]

10 minutes ago, alacant said:

Hi. Use it with EKOS as well? It's much more refined than the internal guider.

 

Could you expand on that? I'm currently using the internal guider .. is it worth me trying PHD?
Does it improve guiding, or something else? What RMS are we talking about?

 

[alacant]

Hi. The EKOS guider works fine but by comparison is more basic. You have to calibrate for each new target and after a meridian flip. That may however be acceptable for you.

PHD2 automates a lot of the tedium of guiding and in addition, gives you the ability to change guiding algorithm for both axes and control the fine movement of each. 

I'm on eq6 via EQMod and e.g. the ppec for RA is a godsend, something not available via the internal guider.

Lastly, the support for PHD2 is IMHO the best for any piece of software, astro, or otherwise.

HTH

Edited July 5, 2019 by alacant

[wimvb]

On 04/07/2019 at 23:27, upahill said:

A bit out of practice, but the having switched to INDI/Kstars etc I managed to get a few subs last night for the first time, I have stacked them using basic DSS settings and im getting what looks like field rotation/radial banding in the final image. Haven't come across this before and the rotation does appear to be centres on the image itself.

Any ideas what causes this, each individual sub looks ok but there were no calibration subs on this, my only thought so far is that maybe the camera was slipping in the focuser during the night but doesnt seem likely. Hopefully the attached screenshot is large enough to see the effect.

 

Looks like a polar alignment issue to me. If PA is off, the images will seem to rotate around the guide star. DSS will show each image's x and y offset, as well as its rotation relative to the first/reference image.

+1 for using phd as guiding app.

[upahill]

I’m going to give PHD ago I think. I did prefer it. 

I think PA could be way out, or balancing at least - should really switch to a smaller guidescope