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Background Gradients

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#1 cmoran

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Posted 13 July 2018 - 12:26 AM

Hello.

I recently purchased a monochrome ZWO ASI1600MM Pro camera not too long ago and am just beginning to use it. I live in an orange to pink light pollution area. I'm hoping the monochrome camera will make it easier to obtain more pleasing images. Unfortunately I'm still struggling with background gradients.

The attached image shows the start of an image capture for the Cat's Eye nebula. The image on the left is just the blue monochrome portion that somewhat shows the background noise. The image on the right is the combined RGB image. The blue, green, and red monochrome images all have a considerable amount of background noise and gradients. The red is the worst.

Here is the flow I used to generate this RGB (using Pixinsight):

Captured 25 x 180 sec. red
Captured 25 x 180 sec. green
Captured 25 x 180 sec. blue

(Still need to capture H-alpha and Oxygen. Also need to redo luminance.)

Using Astrodon E-Series LRGB filters.

For each of the 3 monochrome results:

Batch pre-processing script (50 flats per color, 50 darks, 100 bias; need to redo the red flats)
Dynamic Crop
Automatic Background Extractor (also tried Dynamic Background Extractor; not much difference)
Cosmetic Correction
Star Alignment
Channel Combination
Color Calibration

I end up with the unpleasing combined image on the right.

What more can I do to eliminate these background gradients and make processing easier? Will less exposure time per capture help? Maybe 1 or 2 minutes per capture instead of 3 minutes with same (or more) total exposure time? Again, I tried Dynamic Background Extraction on both the monochrome and combined RGB image without improvement.

Thanks for your time,
Chris

Attached Thumbnails

  • Picture1.jpg

Edited by cmoran, 13 July 2018 - 01:13 PM.


#2 terry59

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Posted 13 July 2018 - 06:45 AM

If you used the ABE default settings it looks like that. Set the function degree to 2 or 1 instead. I also wonder how well your flats have calibrated. If you can make the file available via dropbox folks can take a look and provide better help.

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#3 cmoran

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Posted 13 July 2018 - 05:35 PM

Increasing the function degree makes a huge difference.  Thank you!




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