Beginner looking for advice - M31

[sza85]

Hi!

I took my first step towards deep sky photography, and purchased a star tracker. Longer lenses are still needed, but with my kit lens (18-55), I took one hour (20x3min + 5 darks + 4 bias + 5 flat) worth of pictures of Andromeda at 55mm (82,5 on Nikon APS-C).

Here is my stack (stacked in Sequator, DSS gave me an error): https://www.dropbox.com/s/2rpyge1vkx30utn/22.tif?dl=0

The final image is attached.

My questions are:

1. Why is the final image's quality so bad? (maybe it's just me but it looks terrible)
2. How could I get some colors at the outskirts of the galaxy? (that blueish / purpleish color) - also, somehow I can't get my head around the color module, don't know why
3. Is the problem with getting colors the shortness of the focal length? (because star colors seems quite realistic)

Here is my "workflow":

- Linear, was bayered, is not whitebalanced
- Autodev: ignore fine detail 2 pixels,
- Crop: pretty heavy, because the galaxy is small at 82mm
- Wipe: correct color and brightness, precision 256x256, dark anomaly filter 3px,
- Develop: redo global stretch, digital development at 49,43%,
- Contrast: dark anomaly filter 3px
- HDR: reveal DSO core, tame highlights
- Bin: 50%
- Decon: manual mask -> star mask
- Life: everything default
- Sharpen: grom mask 2x, strength:110%
- Tracking disabled, final noise reduction: full mask, grain size 4px, smoothness 70%
- Repair: auto star mask, default options

Thanks for any tips guys!

[micheleorsini]

Hi,
that's not a bad starting point! Most probably you'll just need more light frames

I made an attempt with your stacking

22_done.jpg (428.35 KiB) Viewed 5642 times

I'm not completely satisfied, anyway, here are a few considerations

0. Before wiping I've noticed that there is a light fall at the edges ... but you have used flats so this is unexplainable to me
1. mine is too green, but I used the color module and it was a matter of just removing a little on the green channel
2. the second stretch can be done up to 79% but then a strange background comes out, I decided for a second crop to avoid it but I'm quite sure a Startool expert will find the proper solution.
3. stretching: use autodev or develop with the "home in" button (press it many times until it stabilises around one value, then push it a little). I found that autodev might stretch too much if the image is really noisy, otherwise it works fine. Take into account that after stretch the image looks very noisy, but then it will change with contrast, color, life and denoise.
4. use Life -> Isolate and your image will be muuuuch cleaner
5. bin at the very beginning!

Here is my log

--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside ROI Influence] set to [15 %]
--- Bin
Parameter [Scale] set to [(scale/noise reduction 50.00%)/(400.00%)/(+2.00 bits)]
--- Crop
Parameter [X1] set to [60 pixels]
Parameter [Y1] set to [40 pixels]
Parameter [X2] set to [2948 pixels (-60)]
Parameter [Y2] set to [1968 pixels (-40)]
--- 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 [3 pixels]
Parameter [Drop Off Point] set to [100 %]
Parameter [Corner Aggressiveness] set to [100 %]
Parameter [Aggressiveness] set to [75 %]
--- Crop
Parameter [X1] set to [813 pixels]
Parameter [Y1] set to [510 pixels]
Parameter [X2] set to [2109 pixels (-779)]
Parameter [Y2] set to [1407 pixels (-521)]
--- Develop
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [0 %]
Parameter [Digital Development] set to [78.99 %]
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]
--- Deconvolution
Parameter [Image Type] set to [Deep Space]
Parameter [Mask Behavior] set to [De-ring Mask Gaps, Hide Result]
Parameter [Radius] set to [1.5 pixels]
Parameter [Iterations] set to [6]
Parameter [Regularization] set to [1.00 (optimal noise and detail)]
Parameter [Mask Fuzz] set to [8.0 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 [1 pixels]
Parameter [Aggressiveness] set to [75 %]
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 [Reveal All]
Parameter [Dark/Bright Response] set to [1.00]
Parameter [Detail Size Range] set to [20 pixels]
Parameter [Strength] set to [1.2]
--- Color
Parameter [Cap Green] set to [No]
Parameter [Bias Slider Mode] set to [Sliders Reduce Color Bias]
Parameter [Style] set to [Artistic, Detail Aware]
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 [1.10]
Parameter [Green Bias Reduce] set to [1.00]
Parameter [Red Bias Reduce] set to [1.36]
Parameter [Mask Fuzz] set to [1.0 pixels]
--- Life
Parameter [Detail Preservation] set to [Linear Brightness Mask]
Parameter [Compositing Algorithm] set to [Multiply, Gamma Correct]
Parameter [Inherit Brightness, Color] set to [Off]
Parameter [Output Glow Only] set to [No]
Parameter [Airy Disk Sampling] set to [128 x 128 pixels]
Parameter [Airy Disk Radius] set to [8 pixels]
Parameter [Glow Threshold] set to [0 %]
Parameter [Detail Preservation Radius] set to [20.0 pixels]
Parameter [Saturation] set to [100 %]
Parameter [Strength] set to [100 %]
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 [6]
Parameter [Color Detail Loss] set to [12 %]
Parameter [Brightness Detail Loss] set to [12 %]
Parameter [Grain Size] set to [2.0 pixels]
Parameter [Read Noise Compensation] set to [Off]
Parameter [Smoothness] set to [75 %]

[sza85]

Thanks micheleorsini!

Yours look way better. Yes, most probably I need more light frames, and of course this lens isn't that high quality optically. I will do your workflow to see the effects. Thanks again!

[Rkonrad]

Just joining this thread to add a bit of advice re: colour module. When you have noisy or light polluted data - of even if it's good, I find the best way to achieve good accurate colour is to sample a portion of it, then apply the settings to the whole image. I worked on the image a bit, though not super, I got the galaxy colour by sampling the galaxy only and subtracting the stars (not sure if the latter was necessary). I like Michele's better in general but this has less green,

m31-bin.jpg (446.99 KiB) Viewed 5513 times

So the steps would be
1. Mask the galaxy (or a part of it)
2. Go to "auto" "stars" and specify the size (half of default is good)
3. Select "subtract new from old"
4. When done, invert the mask so you can see if the stars were masked properly
5. Under the colour module, select mask, clear, invert. This will apply the white balance achieved by the masking to the whole image.
Masking the galaxy alone may be good enough though.

Nice data actually and considering it was a kit lens! Assuming you shot wide open (f5.6), an hour is not too bad. Detail is all about a longer focal length. I shoot with a 300mm zoom lens and actually the image I posted in the gallery is about half the amount of light you got (maybe darker skies than you?), so your image would be dramatically improved with a telephoto lens.

Cheers Richard