RGB Noise?

Questions and answers about processing in StarTools and how to accomplish certain tasks.

RGB Noise?

Postby Todd1561 » Tue Apr 17, 2018 2:23 am

I'm starting to get more into imaging and have been trying to learn more about post processing methods.  I'm following this guide: http://astro.ecuadors.net/processing-a-noisy-dslr-image-stack-with-startools/  But I'm finding after the initial AutoDev (and amplified by the wipe module) I'm getting significant RGB noise I can't get rid of it even after I finish the process outlined in article.  Does anyone know what might be going on here?  My original capture was with a NexStar 6se, 0.5x FR, and ASI224MC.  I used SharpCap to do the capture and stacking and I exported a 32-bit FITS without any stretching which I'm putting directly into StarTools.  10s subs x 37 frames.  350 gain.  I did not use any dark or flat frames, which might be part of the issue.  I'm including the images below.


Noisy image:


Original FITS:
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Re: RGB Noise?

Postby admin » Thu Apr 19, 2018 7:01 am


You should be able to push back the noise while doing the 2nd AutoDev (e.g. during the final global stretch). Just specify a Region of Interest over M51's disc;
StarTools_080.jpg (139.65 KiB) Viewed 1133 times

The problem is that, by default, AutoDev will optimize for the whole image, which may not necessarily be totally of interest. Here the whole image is mostly background, with a comparatively small area being actual object. WHat happens then is that it will start trying to bring out the background more (as there is relatively more of it).

Apart from that, I have a feeling SharpCap is still pre-stretching (as well as color balancing). Noise is visible, even in the unstretched version, which is fairly rare... Have you got any other software at your disposal to do the stacking with?
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Re: RGB Noise?

Postby Todd1561 » Fri Apr 20, 2018 2:54 pm

Interesting, thanks for the input. I'm using SharpCap because it's convenient for doing EAA and also saving the stacked frames all in one package. I have been suggested to try APT and then presumably stack in DSS. I'll give that a shot the next time I'm out and see what happens. I might have also been pushing the gain a little too far on the camera.
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