Newby having hard time with M13

[N_DD]

Hi!

first of all I would like to thank the developers: I really like Star Tools and the "philosophy" behind it!

However, I am having some hard time processing M13: I acquired a series of exposures (5x8min+5x4min+5X2min) using a C8+FR (f=1260mm) and a modified DSLR and stacked them using DSS. The resulting image shows a red cast (caused by the increased red sensitivity and by the red-zone light pollution I am imaging from). I have tried to get rid of this color both using Wipe (cropping the image and carefully masking the dust doughnuts and other stacking artifacts) and the color module, but without success (I am using the latest demo version). Is there anything else I might try to correct the tone of the image?
The stacked image is available here https://www.dropbox.com/s/zu76bh4efox4ec8/M13.FTS

Thanks!

Nico

[Cheman]

Nico
I took a shot at this, and I may have taken a couple of wrong steps, but really quickly, I just cropped a bit and binned, and did a wipe with increased corner aggression then launched the color module. Didnt do anything else cause I just wanted to see what I could get fast. Am I on the right track as to what you want?
Che

M13.jpg (130.47 KiB) Viewed 7390 times

File loaded [C:\Users\Dave\Desktop\M13.FTS].
---
--- Bin
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [50.82 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [Off]
--- Crop
Parameter [X1] set to [26 pixels]
Parameter [Y1] set to [30 pixels]
Parameter [X2] set to [1931 pixels (-22)]
Parameter [Y2] set to [1274 pixels (-27)]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [1 pixels]
Parameter [Drop Off Point] set to [0 %]
Parameter [Corner Aggressiveness] set to [118 %]
Parameter [Aggressiveness] set to [75 %]
Undo.
--- Crop
Parameter [X1] set to [45 pixels]
Parameter [Y1] set to [59 pixels]
Parameter [X2] set to [1764 pixels (-141)]
Parameter [Y2] set to [1210 pixels (-34)]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [7 pixels]
Parameter [Drop Off Point] set to [0 %]
Parameter [Corner Aggressiveness] set to [150 %]
Parameter [Aggressiveness] set to [75 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [49.46 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [100 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [3.7 pixels]
--- Color
Parameter [Cap Green] set to [To Brown]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [StarTools True Color Constancy]
Parameter [LRGB Method Emulation] set to [Straight CIELab Luminance Retention]
Parameter [Dark Saturation] set to [2.00]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [200 %]
Parameter [Blue Bias Reduce] set to [1.00]
Parameter [Green Bias Reduce] set to [1.44]
Parameter [Red Bias Reduce] set to [2.70]
Parameter [Mask Fuzz] set to [1.0 pixels]
File saved [C:\Users\Dave\Desktop\M13.jpg].

[admin]

Hi Nico,

Thanks and welcome to the ST forums!
I like what Che already did with your data and I had a look myself as well.
It appears the data has been stretched already (and the color has been meddled with - it seems to be clipping).
You didn't shoot in JPEG did you? If not (you shouldn't!) and you used RAWs, did you import those straight into DSS?

[N_DD]

Thanks Che!

I like your result: however, I still feel the colors are bit too "warm" and that I am missing some saturation. Maybe it's because I am used to the "canonical" way of displaying such images, which could differ from what one gets by using a more scientifically accurate palette…

Ivo: I am shooting RAW, imported directly into DSS and the result is what came out of the alignment+stacking (no post processing). Maybe I am using too long exposures for my light polluted backyard (although the histogram's peak of the longest subs is between 1/3 and 1/2 of the full dynamic range). I will try stacking only shorter subs and see if I can improve the results.
BTW, how did you check for stretch/color clipping?

Thanks a lot!

Nico

[admin]

Thanks Che!

I like your result: however, I still feel the colors are bit too "warm" and that I am missing some saturation. Maybe it's because I am used to the "canonical" way of displaying such images, which could differ from what one gets by using a more scientifically accurate palette…

Ivo: I am shooting RAW, imported directly into DSS and the result is what came out of the alignment+stacking (no post processing). Maybe I am using too long exposures for my light polluted backyard (although the histogram's peak of the longest subs is between 1/3 and 1/2 of the full dynamic range). I will try stacking only shorter subs and see if I can improve the results.
BTW, how did you check for stretch/color clipping?

Thanks a lot!

Nico

Aha! I just re-read your original post and realized your stack is a composite of different exposure lengths.
This is the source of your troubles; StarTools cannot recover correct colors or noise levels or with such data, as these may vary all over the place (especially if you chose the entropy-based image merging).
If you want to make a HDR composite (which should be unnecessary for all but the brightest of DSOs such as M42), process each (aligned) stack separately and use the simple procedure shown towards the end of this video to combine the two stacks.

Alternatively, you could process the stack as-is and save the result (Che's result is great for example, except for the colors). Then open up an (aligned) stack of a single exposure length and do a simple processing of this stack, for which colors should be recoverable. A Wipe and color calibration should be enough. Then you can combine the luminance information of the earlier (composite) stack and the color of the stack we just processed into a new image that uses one for the luminance information and the other for color. You can do this in the Layer module (use Color of fg for the Blend mode).

[N_DD]

Ivo, thanks!

I quickly tried and stack only subs with the same exposure using "average" combination, and the results are much better now: I can get better colors and saturation!
Maybe this topic has been already discussed in the forum, but what are the best options to use in DSS for getting the best out of Startools?

Thanks a lot!

Nico

[admin]

Ivo, thanks!

I quickly tried and stack only subs with the same exposure using "average" combination, and the results are much better now: I can get better colors and saturation!
Maybe this topic has been already discussed in the forum, but what are the best options to use in DSS for getting the best out of Startools?

Thanks a lot!

Nico

Great! Roughly the best settings look similar to these; (e.g. a lot of "no's" )

Screenshot-Save As.png (32.44 KiB) Viewed 7354 times

Screenshot-Stacking Steps-1.png (36.8 KiB) Viewed 7354 times

Screenshot-Stacking Steps-2.png (40.21 KiB) Viewed 7354 times

Depending on your camera, even better is if you could use dcraw from the command line with some specific settings to debayer the data before DSS gets to do it.