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"Purple haze" left behind after dark subtraction?  

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(@chris_h)
Molecular Cloud Customer
Joined: 2 years ago
Posts: 3
September 23, 2020 01:50  

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 1 month ago by chris_h

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(@mestutters)
Neutron Star Customer
Joined: 3 years ago
Posts: 108
September 23, 2020 11:36  

@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 Customer
Joined: 2 years ago
Posts: 3
September 23, 2020 15:06  

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 Customer
Joined: 2 years ago
Posts: 3
September 27, 2020 01:57  

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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