Author Topic: Help!! Processing Barnard 150  (Read 934 times)

Offline vkohli

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Help!! Processing Barnard 150
« on: 2016 July 18 03:13:31 »
Dear ALL,

I was wondering if anyone would like to take a stab at processing my Barnard 150 data (~12 hrs of data; SNR is low due to short subexposures of 10mins). Despite having correct star colors, my sky background is not correct. I have attached a link to the files, and included my own processed version. In my processed version, I managed to get a proper sky background color, but for some reason I cannot seem to replicate the results  starting from scratch (I wanted to reprocess the data again and add a few tweaks).  I'm thinking that the incorrect color background is coming from improper use of DBE/ABE. However, after DBE/ABE is usually do a superbias on the image to check the gradient. To me it looks fine. The LRGB files have already been calibrated, registered, subframe selected, and drizzled. No cropping or DBE/ABE have been performed. I'm really struggling to find out where I am going wrong. If you could please provide a detail processing outline, it would help me very much. Just for reference this is the processing approach I have taken:

Link to files:  https://www.dropbox.com/sh/lblrjrkg1blhjen/AAB7Pyze8G54zsys2lGkd7sYa?dl=0

1. Image calibration (bias, flats, and darks; flats using a flat pannel), subframe select, registration, and integration all channels. Drizzle applied.
2. Dynamic crop images
3. Apply DBE/ABE (bg subtraction) - I check the bg model, and sometimes run a superbias on the resultant image to confirm proper gradient removal.
4. Linear fit - fit to the brightest channel
5. ChannelCombination
6. Bg neutralization
7. ColorCalibration - for the white reference I use the entire image and enable structure detection (6,1). - At this point the star colors look great but the bg color does not.
8. Masked stretch - 100 iterations or more
9. Nonlinear stretch of Lum data via histogram transformation.
10. LRGB combine L with RGB.
11. Various curve transformations using in combination with range selection masks.
12. Finish off with TGVdenoise.

As mentioned my first attempt at processing this object did produce correct bg sky color. But, I can't seem to duplicate the results. This is driving me nuts! I would really like to see what other pixinsight users would do, and hopefully find out where I am going wrong.

Thanks for your help!
Vik

Offline biosif

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Re: Help!! Processing Barnard 150
« Reply #1 on: 2016 July 24 12:00:38 »
Hi.
That's my version processing. Your videos contain much information, but with patience comes to the surface. You have two links how to proceed, follow the instructions and you'll have a beautiful result.

https://www.youtube.com/watch?v=zqhLKIjGMXA
https://www.youtube.com/watch?v=knKTsNfohzg

My version.
Astrotech AT8IN, CGEM, Atik 314 L+

Offline Alejandro Tombolini

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Re: Help!! Processing Barnard 150
« Reply #2 on: 2016 August 21 03:35:03 »
Hi Vik, thank you for sharing your data, it is a challenge object. Here is my try and the description of the processing steps.
Saludos, Alejandro.

Offline biosif

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Re: Help!! Processing Barnard 150
« Reply #3 on: 2016 August 21 09:38:27 »
[quote author=Alejandro Tombolini

Hi.
I like your example of processing, but i can't find GammaStretch tool.
And in this line you give an link. Now I built a mask as described in this article (underconsturction) to support the use of intensity tranforamtion to give constrast to the image.
But this link is dead.

Thankyou.
Astrotech AT8IN, CGEM, Atik 314 L+

Offline Alejandro Tombolini

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Re: Help!! Processing Barnard 150
« Reply #4 on: 2016 August 21 22:32:44 »
Hi biosif, yes the mask article is still under construction. In the meanwhile i will try to extract those process icons from the project and upload them. That will allow you to make both mask.
Regarding GammaStretch, is one of the Carlos' modules. See here where they are located and how to install modules.
Saludos, Alejandro

Offline Alejandro Tombolini

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Re: Help!! Processing Barnard 150
« Reply #5 on: 2016 August 22 00:07:20 »
Hi biosif, attached are the process icons.
Saludos, Alejandro.