M13 workflow improvement

[deanST]

looking for advice on how I can improve my workflow on this subject (and other star clusters).
Apologies, I couldn't cipher out BBCode so that clicking the thumbnail links to the larger posting
with acquisition details. In short: 5 hrs over 4 nights, pruned 682 down to 610 with ASTAP analyse
and organise images, bias/darks/flats/lights calibrated in Siril, processed in StarTools 1.7.457 (Linux64-GPU).
My GT71 may have "pinched" optics as evidenced from iron cross star halos. Dithered 2 pixels every 5 frames.

details+:
https://telescopius.com/pictures/view/8 ... er/by-dl_i
source .fits:
https://drive.google.com/file/d/1Zvkler ... sp=sharing

workflow:

Code: Select all

-----------------------------------------------------------
StarTools 1.7.457
-----------------------------------------------------------
Image size is 3008 x 3008
--- 
Type of Data: Linear and was Bayered, but not whitebalanced
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [0 pixels]
Parameter [RoI Y1] set to [0 pixels]
Parameter [RoI X2] set to [3008 pixels (-0)]
Parameter [RoI Y2] set to [3008 pixels (-0)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [50 %]
--- Crop
Parameter [X1] set to [80 pixels]
Parameter [Y1] set to [501 pixels]
Parameter [X2] set to [2928 pixels (-80)]
Parameter [Y2] set to [2507 pixels (-501)]
Image size is 2848 x 2006
--- Wipe
Parameter [Synthetic Dark/Bias] set to [Adaptive Multi-Axis Bias Aggressive]
Parameter [Gradient Edge Behavior] set to [Grow opposite axis]
Parameter [Synthetic Flats] set to [Vignetting]
Parameter [Sampling Precision] set to [256 x 256 pixels]
Parameter [Dark Anomaly Filter] set to [4 pixels]
Parameter [Gradient Falloff] set to [75 %]
Parameter [Synth. Bias Edge Area] set to [100 %]
Parameter [Gradient Aggressiveness] set to [50 %]
Redoing stretch of linear data
--- Auto Develop
Parameter [Ignore Fine Detail <] set to [Off]
Parameter [Outside RoI Influence] set to [15 %]
Parameter [RoI X1] set to [1302 pixels]
Parameter [RoI Y1] set to [881 pixels]
Parameter [RoI X2] set to [1601 pixels (-1247)]
Parameter [RoI Y2] set to [1155 pixels (-851)]
Parameter [Detector Gamma] set to [1.00]
Parameter [Shadow Linearity] set to [30 %]
--- Contrast
Parameter [Expose Dark Areas] set to [Yes]
Parameter [Brightness Retention] set to [Off]
Parameter [Precision] set to [256 x 256 pixels]
Parameter [Shadow Detail Size] set to [10 pixels]
Parameter [Locality] set to [50 %]
Parameter [Shadow Dyn Range Alloc] set to [50 %]
--- 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 [Full]
Parameter [Detail Size Range] set to [1000 pixels]
Parameter [Strength] set to [1.2]
--- Wavelet Sharpen
Parameter [Structure Size] set to [Large]
Mask used (BASE64 PNG encoded)
--- SNR-aware Wavelet Sharpening
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [100 %]
Parameter [Scale 5] set to [100 %]
Parameter [Mask Fuzz] set to [4 pixels]
Parameter [Amount] set to [415 %]
Parameter [High SNR Size Bias] set to [85 %]
Parameter [Low SNR Size Bias] set to [0 %]
Parameter [Dark/Light Enhance] set to [50% / 50%]
Mask used (BASE64 PNG encoded)
--- Color
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 [Matrix] set to [Identity (OFF)]
Parameter [Dark Saturation] set to [2.9]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [233 %]
Parameter [Blue Bias Increase] set to [1.00]
Parameter [Green Bias Increase] set to [1.08]
Parameter [Red Bias Increase] set to [1.28]
Parameter [Mask Fuzz] set to [1.0 pixels]
Parameter [Cap Green] set to [0 %]
Parameter [Highlight Repair] set to [1 pixels]
Mask used (BASE64 PNG encoded)
--- Deconvolution
Parameter [Image Type] set to [Deep Space]
Parameter [Secondary PSF] set to [Dynamic Star Sample Small x Primary]
Parameter [Primary PSF] set to [Moffat Beta=4.765 (Trujillo)]
Parameter [Primary Radius] set to [1.6 pixels]
Parameter [Iterations] set to [11]
Parameter [Error Diffusion] set to [Off]
Parameter [Mask Fuzz] set to [8.0 pixels]
Parameter [Deringing] set to [50 %]
Mask used (BASE64 PNG encoded)
--- Unified De-Noise
Parameter [Grain Size] set to [5.5 pixels]
Parameter [Walking Noise Size] set to [1.0 pixels]
Parameter [Walking Noise Angle] set to [0]
--- Unified De-Noise
Parameter [Scale 1] set to [100 %]
Parameter [Scale 2] set to [100 %]
Parameter [Scale 3] set to [100 %]
Parameter [Scale 4] set to [95 %]
Parameter [Scale 5] set to [73 %]
Parameter [Grain Equalization] set to [0 %]
Parameter [Scale Correlation] set to [50 %]
Parameter [Color Detail Loss] set to [50 %]
Parameter [Brightness Detail Loss] set to [50 %]
Parameter [Grain Dispersion] set to [6.7 pixels]
--- Photographic Film Development Emulation
Parameter [White Calibration] set to [Use Stars]
Parameter [Gamma] set to [1.00]
Parameter [Skyglow] set to [2 %]
Parameter [Digital Development] set to [Off]
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 [5.0 pixels]

[admin]

Hi!

There is nothing really wrong with this workflow.

The biggest opportunities for improvement lie with your dataset and acquisition.
Your flats don't appear to work that well and I can spot walking noise. I might be wrong, but some sort of filter (other than UV/IR cut) appears to have been used?

Your dataset is a little oversampled (and stars are not perfectly round across the entire field - this is really a nitpick though!), so you stand to gain by binning it a little, which in turn will let algorithms achieve better results with the cleaner signal.

You can probably dispense with the Contrast module - it is meant for medium-to-large areas, but the globular cluster is comparatively small.

HDR's Reveal Core and/or Tame preset should be enough to tame the core. The Sharp module's DSODark preset will resolve the core more, but the big gun is obviously deconvolution - it is usually best to do that before Color calibration.

If the background is uneven but otherwise "uninteresting", you could use the Super Structure module to push back the noise.

Don't use a global stretch after switching Tracking off. Do your global stretch once at the start. It should never be necessary to do another stretch very late in the workflow and particularly when Tracking is off; it negates all decisions you made earlier and changes noise relationships again (but this time Tracking cannot track or use these statistics).

Lastly, consider using the Walking Noise Reduction (docs here) to mitigate the streaking noise caused by not dithering (and consider dithering going forward if partical!).

You would end up with something like this;

m13_1_2_3_4_siril_stacked_202103_05-10.jpg (494.96 KiB) Viewed 2100 times

[deanST]

thanks Ivo!
I dither every 5 frames but maybe I should increase the number of pixels
and/or increase the frequency. I only have a ZWO UV/IR cut filter in the path.
I adjusted my backfocus one of the 4 nights (the not perfectly round star issue), took flats for that session,
and the rotation on that one night was 1 degree different according to plate solving. I calibrated each
night set of lights separately, de-bayered and pruned out the bad ones with Astap and then added them all
to Siril for alignment and stacking. Probably it was tinkering with different flats within the same subject
led to the walking noise and regardless is not a good plan.

My idea for using the film dev after tracking is off was
only to boost the sky glow a few % so the background wasn't pitch black. I had comments on other forum
posts of my AP about the black point being too low.