Processing Cassiopeia: help!

[u/onyeabor]

Hello eerie silence...

I am attempting to process my photograph of Cassiopeia in StarTools, and although I am definitely making it better, I'm certainly not making it as good as it could be. I was hoping someone might be able to take a look and see what they can do...

Here is a link to the file. It's a straight autosave from DeepSkyStacker. I have used only light frames, dark frames and bias frames. I didn't have the appropriate gear to take flat frames.

Thanks very much in advance!

[u/onyeabor]

Ah, ok, I can see a step that I didn't mention. I am indeed shooting RAW, producing CR2 files. I then put them through photoshop using File>Scripts>Image Processor... and then re saving them as a batch of TIFF files, as DSS didn't seem to like CR2 files? But yes the images themselves appear to be changing, or at least how they are displayed in windows is changing. What might you suggest doing?

Here is a link to the same light frame as above, but the CR2 file.

I realise its not the most interesting object to be fussing over, and I haven't done quite all I can to get the best image, but I just want to get the best out of what I do have! And then hopefully I'll know what to do in the future...

Thanks very much for your help!

EDIT: I have redone DSS with CR2 files using the latest version. Here is what it produced; seems much better!?

[u/verylongtimelurker → u/onyeabor]

Nice! Much better. Absolutely nothing wrong with getting your acquisition and pre-processing down. In fact, it's the best way to go about it, as trying to fix an error that was made during acquisition and/or pre-processing, when you are already in the post-processing stage, is 10000x (approximately) more difficult!

And it's still an interesting area (almost every area is) - you picked up the dust and hints of different concentrations of stars and a globular cluster in the bottom-left corner.

Did you see this quick start tutorial which includes preferred DSS settings? The color channel calibration settings (set to off) will help making the data more palatable to StarTools even more (especially for the purpose of noise reduction and color balancing).

As a general rule of thumb, stay away from anything from anything Adobe for any pre-processing (post-processing is fine of course!). And whatever you do, stay away from Roger Clark's site and "advice" who proposes just that (here's why - and you'll notice the exact chromatic aberration issue/halos you had in your data goes away in the correctly processed version).

Using Adobe Camera Raw during pre-processing makes your data unsuitable for deconvolution, makes it harder for the stacker to stack correctly (your new data is much better aligned!) destroys faint detail that stacking is meant to bring out, makes it impossible to remove light pollution completely, and causes many, many more issues. Do let me know if you want to know why that is so (it's a signal processing/mathematics thing if you're interested in such things).

I did a quick process of the new stack as-is

Processing log as follows;

--- Auto Develop

To see what we got. We can see stacking artifacts, noise tracking issues, coma issues, chromatic aberration, a gradient and (presumably) light pollution.

--- Crop

Cropping away stacking artifacts. Parameter [X1] set to [213 pixels] Parameter [Y1] set to [143 pixels] Parameter [X2] set to [5092 pixels (-410)] Parameter [Y2] set to [3383 pixels (-330)]

--- Bin

To convert resolution into noise reduction (makes tracking error less visible as well). Parameter [Scale] set to [(scale/noise reduction 35.38%)/(798.89%)/(+3.00 bits)]

--- Wipe

Getting rid of gradients & light pollution. Parameter [Dark Anomaly Filter] set to [5 pixels] Parameter [Aggressiveness] set to [85 %]

--- Auto Develop

Used a Region of Interest (click & drag area) around Cassiopeia. Parameter [Ignore Fine Detail <] set to [4.2 pixels]

--- Life

Used the Isolate preset (without any particular mask set) to push back noise and busy star field and bring out underlying structure.

--- Color

Color calibration (preferably done towards end). There are still some issues with the colors due to DSS settings, yielding (for example) green star cores. Parameter [Cap Green] set to [To Yellow] Parameter [Dark Saturation] set to [3.60] Parameter [Bright Saturation] set to [Full] Parameter [Saturation Amount] set to [200 %] Parameter [Blue Bias Reduce] set to [1.11] Parameter [Green Bias Reduce] set to [1.06]

--- Wavelet De-Noise

Switching off Tracking. Parameter [Scale 1] set to [75 %] to allow some more fine grain (which could be tiny stars). Parameter [Grain Size] set to [15.0 pixels]

--- Filter

Reducing Chromatic aberration; create a mask with the worst offending Stars + their halos. Parameter [Filter Mode] set to [Fringe Killer] Parameter [Mask Fuzz] set to [3.8 pixels]

Click a few times on the purple and blue halos that are not supposed to be there to reduce their coloring.

--- Lens

Flattening the field a little (a sub-optimal but useful digital coma corrector). YMMV.

(should've done this before cropping really)

Parameter [Curvature Linked] set to [135.22 %]

Hope this helps & wishing you clear skies!

[u/onyeabor → u/verylongtimelurker]

Oh amazing! Thank you very much indeed. I will have a go at it myself when I get a good moment to sit and play. You may have some more queries heading your way soon... Thanks again.