M-101 Pinwheel colors

Questions and answers about processing in StarTools and how to accomplish certain tasks.

M-101 Pinwheel colors

Postby RICH-DSO » Wed Sep 05, 2018 2:18 pm

Hi everyone,
I am new to astrophotography and StarTools. My equipment consists of a SCT 235mm F/6.3 and ccd camera.

I am making great progress but have a question regarding colors.
<< How would a user know the correctness of the colors in StarTools. Are colors an interpretation of what the object should look like or can the software accurately represent the colors based on the equipment used. Having a slow telescope, I am not certain if I have maximized the M-101 dataset?>>

I have attached M-101 processed with StarTools. The dataset is a DSS stack of 30 frames of 100 sec.

I used the following StarTools workflow to produce the dataset: 1- DSS stack with recommended options (TIF file embed adjustment in the saved file but do not applied) 2- Crop image 3- Vignetting ~80% 4- AutoDev (background changed to 1%, ignore fine details below 10 pixels) 5- Color (no change to settings) 6- Save

A big thank you to Ivo and StarTools software for improving the quality of my images.

M101-small image for forum.jpg
M 101 3000 sec exposure
M101-small image for forum.jpg (36.25 KiB) Viewed 819 times
Posts: 14
Joined: Tue Sep 04, 2018 9:02 pm

Re: M-101 Pinwheel colors

Postby happy-kat » Wed Sep 05, 2018 8:49 pm

That's a great image to build on.
Could you use the autosaved fits file output from DSS? That is the preferred approach I gather.
I am not sure but it could be you need much more data to get colour showing up.
Posts: 61
Joined: Sun Feb 01, 2015 11:31 am

Re: M-101 Pinwheel colors

Postby RICH-DSO » Wed Sep 05, 2018 9:45 pm

When you suggests to get more data, do you mean longer exposure or more frames with the same 100 sec exposure time?
Thank you for the reply .
Posts: 14
Joined: Tue Sep 04, 2018 9:02 pm

Re: M-101 Pinwheel colors

Postby RICH-DSO » Thu Sep 06, 2018 4:16 pm

Ivo was kind to share his workflow to get the colors out of my Pinwheel dataset.

If you have a SCT F10 (slow) scope using a reducer 0.6 and Atik ccd camera. This workflow could be used to process your image.

See the attached image using this workflow and compare it to the one I processed. This workflow has improved the colors from my dataset.

The recommended workflow by Ivo for my dataset is:
File loaded
Type of Data: Linear, was not Bayered, or was Bayered + white balanced
--- Auto Develop
To see what we got. Red/yellow bias (consistent with color balanced light pollution often as produced by DSS).
We can see oversampling, some stacking artifacts and vignetting.
--- Crop
Cropping away artifacts and framing the galaxy a bit better.
Parameter [X1] set to [47 pixels]
Parameter [Y1] set to [18 pixels]
Parameter [X2] set to [1305 pixels (-87)]
Parameter [Y2] set to [897 pixels (-143)]
--- Bin
To use oversampling for noise reduction. (we could probably reduce more without losing any detail).
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
Image Size 629 x 439 pixels
--- Wipe
Vignetting preset.
Parameter [Dark Anomaly Filter] set to [3 pixels] to catch any small dark anomalies.
--- Auto Develop
RoI over galaxy.
Parameter [Ignore Fine Detail <] set to [4.3 pixels] in order to ignore fine noise.
Parameter [RoI X1] set to [214 pixels]
Parameter [RoI Y1] set to [137 pixels]
Parameter [RoI X2] set to [375 pixels (-254)]
Parameter [RoI Y2] set to [306 pixels (-133)]
--- HDR
To bring out a tiny bit more of the spiral structure in the core.
Reveal preset.
Parameter [Detail Size Range] set to [672 pixels]
Parameter [Strength] set to [1.2]
--- Color
Final color calibration.
For a spiral galaxy like this, you'd be looking for a yellow core, blueish outer rims, purple/pink HII areas dotted around. Foreground star field should show different temperatures.
The default color balance wasn't too bad but MaxRGB mode revealed an overabundance of green, so I pulled back on that.
Parameter [Dark Saturation] set to [5.60] to introduce more color in the darker regions.
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [210 %]
Parameter [Green Bias Reduce] set to [1.57]
Parameter [Red Bias Reduce] set to [2.06]
Parameter [Cap Green] set to [To Yellow] as a last resort to remove any remaining spurious green (after color balance has been reliably determined!)
--- Wavelet De-Noise
Parameter [Filter Type] set to [Distance Weighted Outlier Rejection]
Parameter [Grain Size] set to [7.4 pixels]
--- Wavelet De-Noise
Matter of taste.
Parameter [Scale 5] set to [0 %]
Parameter [Color Detail Loss] set to [15 %]
Parameter [Brightness Detail Loss] set to [13 %]
Parameter [Grain Size] set to [7.4 pixels]
Parameter [Smoothness] set to [86 %]
File created with the above workflow...
PINWHEEL-IVO-06-09-2018.jpg (49.94 KiB) Viewed 805 times
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Joined: Tue Sep 04, 2018 9:02 pm

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