Non Linear PostProcessing

[mhambuch]

Hi, i am new in the usage of Pixinsight and have a question regarding the non linear post processing. Attached is my linear picture of NGC7000 debayered, cosmetic corrected. Base was 20 raw pictures done with a ZWO ASI183MC PRO (cmos color, RGGB). I struggle with the next steps in order to get a nice colored and non linear pic. Hope one of you can have a quick look in my pic to check if everything looks fine so far in the process. The next steps seems to be histogramtransformation and colorsaturation. I tried those processes but could not manage to have at the end a nicely colored gas nebula. thanks a lot, marc.

[pfile]

well... the attachment is missing. can you try to post it again?

rob

[mhambuch]

hi rob. thx

https://www.icloud.com/iclouddrive/0m4-ioVQjoksRdScVErGUMMlw#C20Finale%5FLineaire%5FABE%5FColorCalib

[Greg Schwimer]

Hi Marc,

I took a quick look. Seems that you had already run photometric color calibration on the image, but possibly without background neutralization enabled. Step back and give it a try with that enabled. Without it, on my screen the initial screen stretch (linked) has a magenta cast. I ran PCC again with background neutralization and that helped. Next I ran SCNR with the defaults to clean up the green.

Taking through an STF_based stretch and then pushing the saturation with curves I don't see a lot going on in terms of color. I attempted to draw some color out using the Color Mask script (under utilities) to create a red mask. I applied this mask, inverted it, and used CurvesTransformation to reduc the green and blue channels slightly, then worked the contrast a little. The caveat with this approach is that the stars are also going to have this applied, which you may not want. You can get around that by adjusting the mask to protect the stars, etc.

Results are below. The version on the left is post stretch with none of the curves work I mentioned.

[mhambuch]

Hi Greg, thanks a lot for your time. Yes i ran photometric color calibration on the picture I have posted. Will do what you suggest. For my understanding, when you say you havent seen a lot going on in terms of color, is this because i use a color ccd (and its limitations) instead of a filter wheel based system ? resp. can i improve this somehow (e.g longer exposure time?)

Thanks

[Greg Schwimer]

What I'm mean is that the channels all seem fairly equal, so the color is coming across as mostly greys. It's possible I got to this result because I ran PCC over the top of what you already did but I don't think that's really it. Could be the nature of your camera, could just be that region looks that way. Could be I would get a different result if I had the unprocessed master. Hard to say. If you want to put a copy of that (from right after integration w/ no other changes) I'm happy to take a peek.

When I adjusted it I was going for the typical "milky way" look of reddish brown. To get this I found the best result by using a red mask (color mask script) and reducing the greens and blues ever so slightly.

Believe it or not I haven't imaged that area so I can't say for sure what it would look like with my camera.

[mhambuch]

Thanks Greg. I uploaded the pic right after integration w/o any other processes applied.
Don't loose too much time on this, if you could just find out if this "lack of color" is due to me not mastering the tool or if there is really no color captured by the ccd.

Greetings from France.


https://www.icloud.com/iclouddrive/0qGzU4a040N0pqL1tKinsjEnw#C20Finale%5FLineaire

[Greg Schwimer]

Hi Marc,

Results seem similar. I went ahead and ran through it again, this time pushing the color and contrast a bit more in a similar way to how I did it previously. It's possible this is just how your camera presents the data and that's not a bad thing. From there it's mostly art. Someone else may indeed have a different spin on it than me.

The data does look pretty good overall. One think I noticed is some artifacts from satellites or similar radiating from the upper left corner. That can be fixed during integration or just by leaving the subs contributing the artifacts out altogether.

I added a process container below showing how I went about it. You can unzip it and load it into PI and run the individual processes to see what I did. For the masks I used the color mask script and an L mask which I created by extracting the L channel. The ~ before the mask in the process container means the mask was inverted when I applied the process. Explaining just in case and for others that are learning.

Le Tour was interesting this year. Alaphillipe was so close...

- Greg

[dld]

Hello,

A checkerboard pattern is visible in the dark areas of the image, when extremely zoomed. My suspicion is that something went wrong during calibration. Also the red channel is nearly the same as the blue channel.  How does the uncalibrated lights looks like? Do they have the expected colors?

[mhambuch]

Hi Greg, dld

Thanks a lot for your time and for the process container, helps me. Yes the tour was very interesting this year, i went to see them the day the crossed my region (Alsace). They climbed what for me is a mountain (les vosges) as if it would be plain, amazing.

for dld, i have added one of my raw shot on iCloud. Debayered and STF boosted autostreched it gives an image that turns red/violet. So from my understanding, it seems that my CCD has not captured many colors? thx

[dld]

for dld, i have added one of my raw shot on iCloud. Debayered and STF boosted autostreched it gives an image that turns red/violet. So from my understanding, it seems that my CCD has not captured many colors? thx

Hello mhambuch,

I will be glad to take a look at your raw files but unfortunately I can't find them. Maybe the iCloud sharing link needs to be updated? Chances are the Bayer pattern you are using during debayering is not appropriate for your sensor. Your camera is probably fine!

[mhambuch]

Hello dld,

I have added one of my raw pic under the following link.

According to ZWO, the ASI183MC has a RGGB pattern.

Thanks for your help

https://www.icloud.com/iclouddrive/0JH9Ch0FKyZMlLaV_PHYoDVOg#Img-16

[dave_galera]

Have a look at this thread, seems others are having problems similar to yours......

https://www.cloudynights.com/topic/545341-pixinsight-debayer-settings-for-asi1600/

[mhambuch]

Thanks a lot Dave, this also helps, will check options

[oldwexi]

@mhambuch,
Your image has excellent colors and is incredible sharp!
Find the link to your image annotated in full size.
http://www.werbeagentur.org/oldwexi/GRBG_clone1_Annotated1.jpg

The Bayer Matrix of your captured image resulted in GRBG  !!!
Using GRBG gives correct Star Colors.

To find out the correct bayer matrix of your image its very simple.
you have 4 possibilities. Those two with RGGB, BGGR  give checkers when you zoom in heavy.
So G cannot be inside the 4 letters. Whats left is either GRBG or GBRG. Doing an STF to these two immediately shows
the red nebula of NGC7000 by using GRBG.

By the way, if this is really a single exposure its a very excellent image!!!#

Gerald