Author Topic: DSLR calibrated images have totally red background, please assist!  (Read 3027 times)

Offline Jfakatselis

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Admittingly I am a newbie to PixInsight but not to astrophotography.  Using v1.8 RC7 on Win 64 bit. Have been using ImagesPlus for my DSLR processing for the past several years but wanted to improve my results with the power of PixInsight.

I have been imaging with my Canon DSLR and producing the bias, darks, flats and lights as is normally done in Canon CR2 Raw format and as I normally process them in my workflow with IP.

In Format Explorer I have set the DSLR_RAW to "Create RAW Bayer Image",  and "No black point correction" as recommended. Both "White balance" options were disabled.

In using the BatchPreProcessing Script, my images come out with what seems to be a red mask on top, both the calibrated and registered light images are very very red with the star field.

My raw input light images, when viewed just after capture have a heavier blue cast due to the Hutech IDAS LPR filter I am using so I know that I'm imputing reasonable data. I would expect the integrated final image and the registered and calibrated images to look somewhat the same, they certainly do not.

Any insight into what I may be doing incorrectly?

Thanks in advance.

Jim



Offline Harry page

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Hi

Welcome to PI  ;D

And you are doing nothing wrong PI does not carry out any auto white balance and if you watch this vid

http://harrysastroshed.com/RGB%20Combination.html

All will be revealed  :D

harry
Harry Page

Offline Jfakatselis

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Thank you I will review it.

Was just thinking that my camera is a modified Canon T1i, modded for extended Halpha sensitivity.

I assume that PI does not compensate for the modified white balance with the gray card image I have stored in the camera. Will look forward to how it can be compensated.

Offline NGC7789

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white balance with the gray card image I have stored in the camera

Keep in mind that the custom white balance used to correct "normal" images taken by a modified camera have no bearing in color balancing an astro photo. A gray card illuminated by sunlight (or any other earthly light source) tells us nothing about the correct colors of stars or nebulae. Even when using this as a custom white balance it's only appropriate for subjects shot in the same light as the grey card. The PI approach is to use an averaged light of many stars (one option being a galaxy and therefore billions of stars) with the assumption being that if you have enough stars this average will correspond to a true white reference.

Offline Jfakatselis

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Thank you for that explanation.

What then is the root cause for the overall heavy red cast?

Offline georg.viehoever

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Its simply the values that come out of your camera. Dont worry about them, the cast goes away once you have done DBE, BackgroundNeutralization and ColorCalibration. To temporarily remove them, use STF: unlink the channels and press the auto button.
Georg (6 inch Newton, unmodified Canon EOS40D+80D, unguided EQ5 mount)

Offline pfile

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light pollution usually manifests itself as a tan/red cast in an OSC image, so that could be a reason for your red cast. it needs to get subtracted out anyway so as georg says, don't worry about it too much unless the red channel is becoming overexposed.

rob

Offline Jfakatselis

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Thank you gentlemen !