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Astrophotography

M20 (Trifid Nebula) Processed with PixInsight
Author Last Post
8/19/2022 7:16 PM
Gary,
When I wrote the info below it was a list but somehow got concatenated upon sending. Sorry if it looks confusing.

Dan
8/19/2022 7:06 PM
Hi Gary,
I have different workflows for OSC, LRGB and narrowband, all variations on a central theme, but here is what I do for OSC.

Weighted Batch Preprocessing script to create master (RGB)
Dynamic Crop and rotate if necessary
Dynamic Background Extraction (gradient removal)
Color Calibration
Extract Luminance for deconvolution
NoiseXTerminator on luminance - linear setting
Histogram Transformation on luminance (set background intensity to about 10%)
NoiseXTerminator on RGB - linear setting
Histogram Transformation on RGB (set background intensity to about 10%)
Combine luminance and RGB
Remove stars
Optionally if green is an issue SCNR
NoiseXTerminator - non-linear
Histogram transformation (set background intensity to about 10%)
Local Histogram Equalization - kernel radius 20 or 40
Local Histogram Equalization - kernel radius 150
Exponential Transformation (usually for galaxies)
Multiscale Linear Transform (sharpening)
Dark Structure Enhance script
Curves
Put stars back (pixel math)
Final Curves
Morphological Transformation (if the stars need some work)
ICC Profile Transformation

Naturally, this is very generic. There are a lot of special situations that necessitate deviations and there are a lot of masks, etc along the way.

Dan
8/19/2022 12:06 PM
Thank you Lou...   and thanks for sharing your PixInsight expertise with the rest of us.  There's still a lot more for me to learn, but I'm feeling encouraged by the results so far.

Gary
8/19/2022 12:04 PM
Thank you Prasad.  Much appreciated!

Gary
8/19/2022 12:02 PM
Hi Dan,

I'm interested in learning more about your workflow when you get a chance.  I've always found comparing notes to be informative.

Gary
8/19/2022 11:44 AM
Thank you Joe!

The M20 data was from the end of May trip to Cherry Springs and was the first time using the C6 (sans reducer/flattener) so the stars aren't very sharp...  partly due to some focuser issues too.  I still have a lot to learn with the tools I'm using now (ASI2600MC-P, ASIAIR, PixInsight, etc.), but overall am encouraged by the results.

Gary
8/18/2022 1:52 PM

Great one, Gary!


Joe
8/17/2022 7:09 PM
Gary, 

That is a beautiful image. 

Prasad
8/17/2022 6:37 PM
Gary, Interesting. We have dramatically different techniques. Thanks for the detail. I'll checkout those links below.

Dan
8/17/2022 5:17 PM
Thanks Dan.  I'm only about two months into PixInsight and have been relying on YouTube tutorials for tackling the learning curve.

Most of the workflow I used for M20 was based on a YouTube video put out by Highpoint Scientific along with another video by Entering Into Space.

My workflow roughly went as follows:

Weighted Batch Pre-processing using Dark, Bias and Flat calibration frames.

Linear Processing:
  • ScreenTransferFunction Autostretch (with color channels unlinked)
  • DynamicCrop (minimal amount just to get rid of alignment edge artifacts)
  • Get rid of green color cast
    • Split RGB Channels
    • LinearFit (using green channel as reference)
    • Channel Combination (to recombine the adjusted red and blue channels)
  • DynamicBackgroundExtraction (DBE)
  • PhotometricColorCalibration
  • ezDenoise script that’s part of the ezProcessingSuite
Non-Linear Processing:
  • HistogramTransformation (a couple of iterations mainly to bring the foreground stars to a good point for making a star mask)
  • Star mask to protect stars from blowing out
  • HistogramTransformation with star mask in place (a few iterations to bring out the nebulosity)
  • CurvesTransformation (mainly to bring down the background and improve contrast)
  • ArcsinhStretch
  • SCNR (with green channel selected)
  • UnsharpMask (slight amount to increase detail without bringing up the noise too much)
  • DynamicCrop (to better frame the image)

For reference, here are the links to the two videos I mentioned above.

Basic Post-Processing with PixInsight Tutorial (2022) | High Point Scientific
https://www.youtube.com/watch?v=V-9MIy0eB6k

Push Your Stars Back and Bring Your Nebula Forward HOO Processing of the Veil Complex
https://www.youtube.com/watch?v=UbU8K-V9uFo


Gary
8/17/2022 5:03 PM

Excellent example of M20 Gary!



Canon EOS Rebel XS (full spectrum mod)

Astronomik CLS CCD

Orion thin off axis guider

QHY5L-II M guide camera

Celestron CGX,Edge HD 8,0.7x focal reducer

Optec TCF-Leo focuser
8/17/2022 3:34 PM
Hi Gary,
Nice result. I am getting started with PI also. I've been at it about 6 months. Can you talk a little about your workflow?

Dan
8/17/2022 2:50 PM

I recently started learning PixInsight and tried reprocessing an image of M20 that I took during a visit to Cherry Springs at the end of May. Even though I still have a lot to learn about PixInsight, I felt that sharing this image with the group might be helpful to me and others as we collectively work our way through the challenges of astrophotography. (I particularly need to learn more about processing with star masks in order to avoid having the foreground stars from becoming too dominant as I bring out fainter details.)


Acquisition details are listed on the image itself.


Clear skies,

Gary
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