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Color streaks post processing problem

Astrophotography
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#1 Jeddymo51

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Posted 03 March 2021 - 12:21 PM

I have attached an image that shows several parallel blue, green and red streaks after stretching in GIMP.  I took two sets of pictures of NGC 2024 last night with different filters.  Astronomik H alpha and Astronomik CLS.  Same session, darks, flats and bias on both.  The streaks only show in the H alpha set.  The filter looks pretty clean.  Used APT to capture.  The thumbnails did not show the streaks, but hard to tell.

 

My setup is an 8 inch Orion Astrograph.  ZWO294.  Gain 200. 90 seconds.  45 images of each filter.  I did not combine them as the H alpha filter image had these streaks.  Used DSS on both.  GIMP in post processing.

 

Could the H alpha filter be causing this?

Attached Thumbnails

  • NGC 2024Ha.jpg


#2 pyrasanth

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Posted 03 March 2021 - 12:25 PM

Those are hot pixels in the sensor matrix. They appear as stripes because they are fixed but your image moves. They can either be fixed by dithering your frames so your software sees the pixels as outliners and removes them or by using cosmetic correction which will target the pixels that fall outside of a norml range and repair them.


Edited by pyrasanth, 03 March 2021 - 12:26 PM.

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#3 Jeddymo51

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Posted 04 March 2021 - 12:51 PM

Thank you.  Thought I was dithering every 3 images.  But makes sense these are hot pixels.  Not something wrong with my filter.  

 

Is there a place where the log from previous APT sessions are kept?  This should confirm whether I had problems dithering or not.



#4 Jeddymo51

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Posted 05 March 2021 - 05:14 PM

I found the log in Tools/Indigo.  No dithering shown.  I had checked that the server is enabled in PHD2, and that APT has all the recommended settings in Gear/Guide.  I'll have to take this issue to another section.  Thanks




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