"Purple haze" left ...
 
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Mar 28 2026 APP 2.0.0-beta40 will be released in 7 days.

It did take a long time to have the work finished on this and it  will have a major performance boost of 30-50% over 2.0.0-beta39 from calibration to integration. We extensively optimized many critical parts of APP. All has been tested to guarantee correct optimizations. Drizzle and image resampling is much faster for instance, those modules have been completely rewritten. Much less memory usage. LNC 2.0 will be released which works much better and faster than LNC in it's current state. And more, all will be added to the release notes in the coming weeks...

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"Purple haze" left behind after dark subtraction?

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(@chris_h)
Molecular Cloud
Joined: 7 years ago
Posts: 3
Topic starter  

Good song, but not something I like to see in my pictures!

To be fair, I didn't really notice it until I made a mosaic. I guess it shows up better when the whole image is resized to fit in the window. But yeah, it seems there is a purple haze left over after dark subtraction. I use a QHY183C, so temp and offset are the same as the lights.

My stack settings are:

0

Ha-Oiii color (Optolong L-eXtreme filter)

1

35 Lights

50 Darks

2

Default settings. Adaptive pedestal/reduce amp-glow is checked

3

Default settings

4

Default settings

5

Default settings

6

Default settings except; 1st degree LNC/3, Enable MBB 5%, Bayer Drizzle

Am I screwing something up here, or is there anyway to tweak this?

I have processed part of the image to show the haze better. Like I said, it is hard to make out in the single image. But once combined into a mosaic, it is easy to spot.

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This topic was modified 6 years ago by chris_h

   
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(@mestutters)
Neutron Star
Joined: 9 years ago
Posts: 175
 

@chris_h

Are you sure this is actually a processing artifact?   I think you are very probably looking at some very faint Ha emissions. 

Take a look at this image and you can see a similar deep red/magenta haze. 

https://www.astrobin.com/302419/?nc=user

Maybe try minor adjustment of Green/Magenta balance.   Very decent image though.  I like the filimentary  blue O3 detail.

 

Mike

 

 

 



   
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(@chris_h)
Molecular Cloud
Joined: 7 years ago
Posts: 3
Topic starter  

Hmmm maybe you are right... I did not see it in other pictures though. If it is real, it should show up in the next panel whenever I get some clear skies again!



   
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(@chris_h)
Molecular Cloud
Joined: 7 years ago
Posts: 3
Topic starter  

Right, I finally finished the Cygnus Loop mosaic, and there is now no doubt there is a purple glow left behind. The new frames covered over the problem area last time, and as you can see - no glow there now. But as we can also see, the new frames have the same glow on the left.

Im only shooting 5 min subs at unity gain, so I don't think the "amp glow" is clipping. Is this a OSC problem? 

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