Quark First Light: Ringing?

[Knight of Clear Skies]

First proper light today for the Quark Chromosphere, using my WO zs71 and ASI 290MC. Shows a great deal of promise but also gives me some idea of just how much work goes into putting together those splendid full-disc mosaics. I shot a few panes but can only get some of them to stack.

Was also very lucky to catch a big prominence, just don't ask me where as I have no idea which way around the camera was mounted.

The first image is showing good detail but there are some prominent ringing artefacts. Does anyone know what's causing this please, and how to remove them?

Both captures were 80 out of 800 frames stacked, I don't know what's sensible in terms of capture length and frame selection. Used PIPP to select the best frames and Registax to stack and sharpen them. The top image has a little curve stretching of the green channel to give it a red-orange hue.

[Davey-T]

4 minutes ago, Knight of Clear Skies said:

The first image is showing good detail but there are some prominent ringing artefacts. Does anyone know what's causing this please, and how to remove them?

The infamous Newtons rings, flats can help as can letting the image drift a bit during capture, using a focal reducer might help, all a bit of suck it and see.

Dave

[tooth_dr]

I recently bought a tilt adapter that successfully remove the rings.  I didnt find flats worked for me, but YMMV.  Good luck with mosaics, not that easy, but then there would be no fun if it was simple.

[Knight of Clear Skies]

1 hour ago, Davey-T said:

The infamous Newtons rings, flats can help as can letting the image drift a bit during capture, using a focal reducer might help, all a bit of suck it and see.

Dave

Would jockying the controls a little during the capture do the trick, or would a little polar misalignment be the way to go maybe?

[Davey-T]

PA drifting would be better as big jumps might not stack.

I use Firecapture, you can take flats and use them when processing, no doubt it can be done with other software, I use cling film over the end of the scope then you don't have to defocus.

Dave

[Knight of Clear Skies]

Good tips thanks. I currently have a diagonal in the imaging train as my plan was to look through an eyepiece first, could that have introduced some tilt? I'll see if I can reach focus without it. If that doesn't help I'll try a cling-film flat.

[GuLinux]

Following with interest, as I have the very same problem.

I still have to try flats, but I did buy a tilt adjuster, which definitely helped  with the newton rings, but the camera is now partially out of focus.

It's quite visible in this picture, the centre is quite sharp, while the borders are visibly out of focus, and the illumination is quite uneven.

[Knight of Clear Skies]

3 minutes ago, GuLinux said:

It's quite visible in this picture, the centre is quite sharp, while the borders are visibly out of focus, and the illumination is quite uneven.

I found a simple PS tutorial here which may help with the uneven illumination.

[Zakalwe]

Make sure that the axis of tilt is along the long axis of the camera sensor. This minimises the distance from the focal plane across the sensor.

Play around with the tilt as well.I have mine set so there is a hint of NRs (which keeps the tilt to a minimum). I usually correct for these faint NRs with a solar flat.

[GuLinux]

2 minutes ago, Knight of Clear Skies said:

I found a simple PS tutorial here which may help with the uneven illumination.

Yes, I already followed that one (the second process, subtracting the blurred image). The image I posted is after I already reduced the uneven illumination, it was a lot worse before  😅

[GuLinux]

6 minutes ago, Zakalwe said:

Make sure that the axis of tilt is along the long axis of the camera sensor. This minimises the distance from the focal plane across the sensor.

Play around with the tilt as well.I have mine set so there is a hint of NRs (which keeps the tilt to a minimum). I usually correct for these faint NRs with a solar flat.

I'll try that, thanks. I often wondered exactly how to find the direction for the tilt, this is indeed a useful suggestion.

 

I still have to learn how to properly do flats (I've read the "cling film" procedure before, I think I've tried it once, but I wasn't really satisfied by it, but I don't remember why. Have to give it another go)

 

Edited May 26, 2020 by GuLinux

[Zakalwe]

1 hour ago, GuLinux said:

.I still have to learn how to properly do flats (I've read the "cling film" procedure before, I think I've tried it once, but I wasn't really satisfied by it, but I don't remember why. Have to give it another go)

 

If you use Firecapture as your acquisition software then you will be able to create flays inside FC and have those applied to the movie stream. It will impact slightly on your FPS, but if your camera has a fast rate then the impact might not be too bad.

 

http://www.urbanastro.co.uk/blog/using-firecapture-to-eliminate-newtons-rings

 

[Zakalwe]

3 hours ago, GuLinux said:

Yes, I already followed that one (the second process, subtracting the blurred image). The image I posted is after I already reduced the uneven illumination, it was a lot worse before  😅

If it's out of focus then no amount of processing will make it as good as an infocus image.

[NiCo10]

Can this be solved with a tilt adjuster?

[GuLinux]

1 hour ago, Zakalwe said:

If it's out of focus then no amount of processing will make it as good as an infocus image.

Yes, of course, I merely meant the illumination issue

[Knight of Clear Skies]

Thanks for the suggestions. I'll remove the diagonal next time and see if I can get focus. If I still have the rings I'll try a cling-film flat and if that doesn't work I'll look at a tilt adaptor. I guess this one would be suitable?

[Merlin66]

That’s the one I use with both my ASI 174 and ASI 1600.

works for me.