Color Module questions

[steve72614]

Hi Ivo,
I've been exploring different ways of processing some M31 images from my Bortle Class 7 skies with a DSLR, 300mm
f4 lens, and a Astronomix CLS light pollution filter.

pass 1
No DSS RGB Background Calibration, StarTools processing log in BLUE at bottom of post. Color is off, noise is
comparitively low.
https://www.flickr.com/photos/stevestar ... 638767931/

pass 2
DSS RGB Background Calibration, StarTools processing log in RED at bottom of post. Color looks closer to correct,
noise is comparitively high.
https://www.flickr.com/photos/stevestar ... 791013248/

I see in the ST manual that you state that color balancing is nearly impossilbe with a light pollution filter. I'm also
aware that if I do white balancing in DSS, then Star Tools can't rely on the extra helping of green input pixel data to
work with. I assume that is why "pass 2" is noisier.

QUESTIONS)
1. The M31 core was overexposed. The Develop module introduced dark artifacts in the core, which I reduced with the
HDR Tame Highlight feature in pass 1. Other than using a shorter exposure, what is the best way to deal with that?
BTW, I did not see similar artifacts of the M31 core with pass 2.

2. In the Color module, how does using the Reduce Green slider effect the image compared to the Cap Green option?

3. Is Cap Green reversible when adjusting the Color Module controls, or must it be the last thing one does in the Color
module?

4. Pass 1 has less noise, and my family likes it better. I do like the colors of pass 2. Should I even be using the CLS
filter for galaxies with Bortle Class 7 skies?

5. Should I relegate the CLS filter to emission nebula?

BLUE----
-----------------------------------------------------------
StarTools 1.3.5.289
Mon Jan 07 17:21:40 2019
-----------------------------------------------------------
File loaded [D:\users\steve\my_docs\astronomy\our astrophotographs\2019-01-04 m31\Autosave.fts].
---
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [15 %]
--- Crop
Parameter [X1] set to [600 pixels]
Parameter [Y1] set to [213 pixels]
Parameter [X2] set to [2200 pixels (-394)]
Parameter [Y2] set to [1413 pixels (-309)]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [Yes]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [4 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [25 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [90.85 %]
Parameter [Blue Luminance Contrib.] set to [100 %]
Parameter [Green Luminance Contrib.] set to [100 %]
Parameter [Red Luminance Contrib.] set to [101 %]
Parameter [Dark Anomaly Headroom] set to [5 %]
Parameter [Dark Anomaly Filter] set to [4.0 pixels]
--- Contrast
Parameter [Expose Dark Areas] set to [No]
Parameter [Compensate Gamma] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [4 pixels]
Parameter [Aggressiveness] set to [70 %]
Parameter [Dark Anomaly Headroom] set to [15 %]
--- HDR
Parameter [Small Detail Precision] set to [Max]
Parameter [Channels] set to [Brightness Only]
Parameter [Algorithm] set to [Tame Highlights]
Parameter [Dark/Bright Response] set to [2.39]
Parameter [Detail Size Range] set to [20 pixels]
Parameter [Noise Suppression] set to [Off]
Undo.
--- HDR
Parameter [Small Detail Precision] set to [Max]
Parameter [Channels] set to [Brightness & Color]
Parameter [Algorithm] set to [Tame Highlights]
Parameter [Dark/Bright Response] set to [4.65]
Parameter [Detail Size Range] set to [20 pixels]
Parameter [Noise Suppression] set to [Off]
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Bias Slider Mode] set to [Sliders Increase Color Bias]
Parameter [Style] set to [Scientific (Color Constancy)]
Parameter [LRGB Method Emulation] set to [Straight CIELab Luminance Retention]
Parameter [Dark Saturation] set to [1.50]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [357 %]
Parameter [Blue Bias Increase] set to [1.00]
Parameter [Green Bias Increase] set to [1.20]
Parameter [Red Bias Increase] set to [3.34]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Wavelet De-Noise
Parameter [Scale 1] set to [90 %]
Parameter [Scale 2] set to [90 %]
Parameter [Scale 3] set to [90 %]
Parameter [Scale 4] set to [90 %]
Parameter [Scale 5] set to [0 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [3]
Parameter [Color Detail Loss] set to [12 %]
Parameter [Brightness Detail Loss] set to [12 %]
Parameter [Grain Size] set to [3.6 pixels]
Parameter [Read Noise Compensation] set to [Off]
Parameter [Smoothness] set to [75 %]
File saved [D:\users\steve\my_docs\astronomy\our astrophotographs\2019-01-04 m31\m31_star_tools_out_v2.tiff].
File saved [D:\users\steve\my_docs\astronomy\our astrophotographs\2019-01-04 m31\m31_star_tools_out_v2.jpg].

RED--
-----------------------------------------------------------
StarTools 1.3.5.289
Tue Jan 08 10:43:20 2019
-----------------------------------------------------------
File loaded [D:\users\steve\my_docs\astronomy\our astrophotographs\2019-01-04 m31\Autosave001.fts].
---
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [15 %]
--- Crop
Parameter [X1] set to [404 pixels]
Parameter [Y1] set to [38 pixels]
Parameter [X2] set to [2404 pixels (-190)]
Parameter [Y2] set to [1538 pixels (-184)]
--- Wipe
Parameter [Mode] set to [Correct Color & Brightness]
Parameter [UNKNOWN] set to [Yes]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [8 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [70 %]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [92.70 %]
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 [4.0 pixels]
--- Contrast
Parameter [Expose Dark Areas] set to [No]
Parameter [Compensate Gamma] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [4 pixels]
Parameter [Aggressiveness] set to [75 %]
Parameter [Dark Anomaly Headroom] set to [15 %]
Undo.
Redo.
--- Color
Parameter [Cap Green] set to [To Yellow]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Scientific (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 [1.03]
Parameter [Green Bias Reduce] set to [1.00]
Parameter [Red Bias Reduce] set to [1.69]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Wavelet De-Noise
Parameter [Scale 1] set to [90 %]
Parameter [Scale 2] set to [90 %]
Parameter [Scale 3] set to [90 %]
Parameter [Scale 4] set to [90 %]
Parameter [Scale 5] set to [0 %]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Scale Correlation] set to [3]
Parameter [Color Detail Loss] set to [15 %]
Parameter [Brightness Detail Loss] set to [15 %]
Parameter [Grain Size] set to [6.4 pixels]
Parameter [Read Noise Compensation] set to [Off]
Parameter [Smoothness] set to [75 %]
--- Contrast
Parameter [Expose Dark Areas] set to [No]
Parameter [Compensate Gamma] set to [No]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [4 pixels]
Parameter [Aggressiveness] set to [57 %]
Parameter [Dark Anomaly Headroom] set to [15 %]
File saved [D:\users\steve\my_docs\astronomy\our astrophotographs\2019-01-04
m31\m31_star_tools_out_from_autosave1_dss_back_cal_medium.jpg].
File saved [D:\users\steve\my_docs\astronomy\our astrophotographs\2019-01-04
m31\m31_star_tools_out_from_autosave1_dss_back_cal_medium.tiff].

Thanks for reading this book!

Steve

[admin]

Hi,

Apologies - I seem to have missed this post...

Hi Ivo,
1. The M31 core was overexposed. The Develop module introduced dark artifacts in the core,

That's odd - the Develop module only performs stretching and does/should not introduce any artifacts.
Can this problem be replicated in the 1.4.x versions?

2. In the Color module, how does using the Reduce Green slider effect the image compared to the Cap Green option?

The Cap Green option is really a last resort measure to remove spurious green coloring, once you are absolutely satisfied that the color balance is otherwise "correct" (in your case, as "correct" as can be with a CLS filter ).

3. Is Cap Green reversible when adjusting the Color Module controls, or must it be the last thing one does in the Color
module?

Every time you change a parameter the Color module calibrates per the settings you gave it and then applies a Cap Green at the end if it switched on. Per my comment above, do please make sure your color balance is as correct as possible, before resorting to the Cap Green function.

4. Pass 1 has less noise, and my family likes it better. I do like the colors of pass 2. Should I even be using the CLS
filter for galaxies with Bortle Class 7 skies?

Galaxies tend to be faint and signal will get quickly overwhelmed by the noise from light pollution, so a filter definitely helps!
I'm not sure if you are using them (my guess is you're not), but it appears you could really benefit from calibration frames (flats are a must) and especially dithering between frames; it will reduce the walking noise. This will give you much cleaner data and backgrounds, making processing much easier. Flats and dithering are hugely effective ways of improving your datasets and their signal. Best of all, they're free! (they just take some time)

5. Should I relegate the CLS filter to emission nebula?

The best thing I can recommend is to experiment a little. Do some session with and without the filter and see how you go.

You can also capture (noisier) color data without the filter and do a second session to capture the detail better with the filter in place. Noise and inaccuracies in the color information is much harder to detect for the human eye (it's what JPEG image compression capitalises on for example).

Lastly, don't process at higher resolutions than you need to. Bin your data until every pixel describes one unit of detail. It will reduce noise as well, while you're not losing any detail (given it was "smeared out" over multiple pixels).

Apologies again for the late reply, but I hope this helps!

[steve72614]

Hi Ivo,
Thanks for your response! Here is the improved result with 1.4.340.
https://www.flickr.com/photos/stevestar ... 139955444/

In the Color Module, the AutoMask with Fat Stars gave me a much better color balance right away. Unfortunately I never saved the mask I used in the Color module in 1.3.5.289, but I think I used the same AutoMask settings. I like that you store masks in the log file now.

That's odd - the Develop module only performs stretching and does/should not introduce any artifacts.
Can this problem be replicated in the 1.4.x versions?

1. On retrying the steps in the original ST log, I see that the M31 core artifacts were caused by the Wipe in 1.3.5.289. When using the same steps with 1.4.340, I no longer see artifacts with the Wipe, and none with Develop. A very minor complaint is that clicking on the individual help setting description icons does not show help text in the Develop module in either version. I'm running Windows 7 64 bit on an i3-540 processor with 4GB of RAM. Star Tools is the 64 bit version for both 1.3.5.289 and 1.4.340.

The Cap Green option is really a last resort measure to remove spurious green coloring, once you are absolutely satisfied that the color balance is otherwise "correct" (in your case, as "correct" as can be with a CLS filter ).

2. Got it!

Every time you change a parameter the Color module calibrates per the settings you gave it and then applies a Cap Green at the end if it switched on. Per my comment above, do please make sure your color balance is as correct as possible, before resorting to the Cap Green function.

3. Got it!

Galaxies tend to be faint and signal will get quickly overwhelmed by the noise from light pollution, so a filter definitely helps!
I'm not sure if you are using them (my guess is you're not), but it appears you could really benefit from calibration frames (flats are a must) and especially dithering between frames; it will reduce the walking noise. This will give you much cleaner data and backgrounds, making processing much easier. Flats and dithering are hugely effective ways of improving your datasets and their signal. Best of all, they're free! (they just take some time)

4. I had 16 flats, 16 darks, and 16 bias frames along with 42 lights. I'm using a Star Adventurer camera tracker with a Raspberry Pi camera autoguider in RA only. I can not do 2 axis dithering with my setup. The "walking noise" is reduced on nights when I have better polar alignment and/or stack more subs.

Lastly, don't process at higher resolutions than you need to. Bin your data until every pixel describes one unit of detail. It will reduce noise as well, while you're not losing any detail (given it was "smeared out" over multiple pixels).

5. Got it! I usually do 2x2 binning with dcraw first. I'm assuming it averages the 2 green pixel values in the original CR2 files from the DSLR.

Thanks Ivo. Version 1.4.340 is looking great!

Steve

[admin]

A very minor complaint is that clicking on the individual help setting description icons does not show help text in the Develop module in either version. I'm running Windows 7 64 bit on an i3-540 processor with 4GB of RAM. Star Tools is the 64 bit version for both 1.3.5.289 and 1.4.340.

Hmmm.... I cannot replicate this with a fresh download. Can you confirm you extraced the full ZIP file contents? Sometime mixing the 'resource' file with a different executable version can cause issues like these...

4. I had 16 flats, 16 darks, and 16 bias frames along with 42 lights. I'm using a Star Adventurer camera tracker with a Raspberry Pi camera autoguider in RA only. I can not do 2 axis dithering with my setup. The "walking noise" is reduced on nights when I have better polar alignment and/or stack more subs.

Gotcha. Even manually pushing the camera a little between frames can make a big difference.

I usually do 2x2 binning with dcraw first. I'm assuming it averages the 2 green pixel values in the original CR2 files from the DSLR.

That's great! No debayering needed that way.

Cheers,

[steve72614]

A very minor complaint is that clicking on the individual help setting description icons does not show help text in the Develop module in either version. I'm running Windows 7 64 bit on an i3-540 processor with 4GB of RAM. Star Tools is the 64 bit version for both 1.3.5.289 and 1.4.340.


Hmmm.... I cannot replicate this with a fresh download. Can you confirm you extraced the full ZIP file contents? Sometime mixing the 'resource' file with a different executable version can cause issues like these...

I was able to simplify a way to replicate the problem with 1.4.340.
1. Load a fts file. Linear, was bayered, not white balanced.
2. Autodev, keep.
3. Develop. Then the control help icons don't do anything.

If one just does step 1 and step 3, the help icons in Develop work fine.

I usually find that Autodev stretches my images too far, and I prefer to use Develop for the final image stretching, so as to have more control.
My typical flow starts with --
a. Autodev to see what's what in the picture.
b. Crop, Wipe, cancel Wipe, and undo Crop, until Wipe produces a good result due to cropping the stacking artifacts.
c. Develop

Steve

[admin]

That was super helpful, thank you!
I can replicate the problem with your description.

Now for a solution...