Author Topic: Need Help - Orion Core Blown Out After Processing  (Read 579 times)

Offline jwaters125

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Need Help - Orion Core Blown Out After Processing
« on: 2019 January 28 22:24:08 »
Last weekend I imaged the Orion complex with a Ha Modified Canon 6D and Canon 200mm F/2.8L II lens at f/3.5.  I shot 60ea Light Subs at 80 and 50 seconds.  I Dithered every other Light Sub.  I also took Darks, Flats and BIAS.  The histogram of the 80 second Light Subs were around 25%.  I was not using any LP filters.  Before imaging I took a Custom White Balance with a gray-card.  PI is set for 'Camera White Balance'.  I was imaging in a Dark Green Zone.

There's color in M42 & NGC 1977 RAW CR2 images but the very center of M42 is somewhat burned out which is OK.  Its very small.

When I process the 80 second subs in PI, stack the Registered subs together and apply STF the vast majority of M42 is blown out along with NGC 1977.  Many times the RAW images show more color than the processed images using PI.

PixInsight Steps
- BatchPreprocessing - Lights, Darks, Flats and BIAS (Rejection Algorithm - Sigma / Combination - Average)
- ImageIntegration (Combination - Average / Normalization - Average / Rejection Algorithm - Sigma Clipping)
- SFT
- DynamicBackgroundExtraction (Correction - Subtraction). Also tried AutomaticBackgroundExtraction (Correction - Subtraction)

Why is M42 and NGC 1977 nebulosity blown out - all white?  Why do the RAW CR2 images look 'bleached' after aligning, stacking and a little processing?

« Last Edit: 2019 January 28 22:50:14 by jwaters125 »

Offline Geoff

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Re: Need Help - Orion Core Blown Out After Processing
« Reply #1 on: 2019 January 28 23:24:38 »
This kind of question is impossible to answer without seeing some examples of the images. You need to load them somewhere so that people can access them and then try to diagnose the problem.
Geoff
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Offline jwaters125

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Re: Need Help - Orion Core Blown Out After Processing
« Reply #2 on: 2019 January 29 00:30:09 »
I will post images tomorrow AM.

Offline sreilly

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Re: Need Help - Orion Core Blown Out After Processing
« Reply #3 on: 2019 January 29 05:20:05 »
While I dont use a dSLR from what you're saying it sounds like you processed all these 50 and 80 seconds images and combined them. What were the total number of images used to combine the final? And what is a Ha Modified camera? From what I've seen this is modified to boost Ha signal and still be a color camera? Anyway, after combining the images it sounds like you used the screen transfer function (STF) which does a decent job of a stretch but doesn't actually stretch the image, it's simply for viewing. Then using DBE for correcting any background vingyetting.  At this point I would have used Photometric Color Calibration or some other means to correct the color balance and then take the image from linear to nonlinear (stretched) by using either Histogram Stretch or Masked Stretch. I usually use curves correction to boost contrast after using Masked Stretch. At this point you should have a fairly well balanced image. But a word of advice, pictures really help here and there are many ways to get to a finished image. My approach with my 12.5" RC and STL-11000M was taking 30, 60, 120, 300 , and 600 second images processed as 5 individual images and then the masters combined using High Dynamic Range Composition (HDRComposition). The resulting image gives you far better results covering from the very lowest signal to the very brightest.

I don't use Batch Preprocessing as I'm a bit of a control freak but primarily because I use a rotator and the last time I looked PI doesn't differentiate between E/W pier side images. I guess I could do all east side and then west but I'm old and like doing the image calibration, cosmetic correction, alignment, and image selection (culling) separately. I feel this gives me more control over the process. Not knocking those who use it, just isn't for me. But then with your camera don't you need to debayer the images and then combine?

-Steve
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