IC1805 and IC1848 with stock DSLR: feedback on workflow and postprocessing

[polslinux]

Hello all,
a couple of nights ago I finally had a crystal clear night after weeks of clouds, so I decided to pull an almost-all-nighter and image something from my balcony.
The targeted DSOs were the Heart and Soul nebulae. Here's the hardware I've used:

• Nikon D7500 stock
• Tamron 150-600 G2
• iOptron SkyGuider Pro

and here's some data:

• Bortle 5/6 location (SQM 19.63)
• 177 lights @ 170mm, ISO 100, f/5, each 1m45s long
• 20 darks taken after the lights
• 75 flats taken the next morning using a lightbox (this one in particular: https://www.amazon.com/NXDRS-Tracing-Ut ... B07D57BQM6)
• 75 dark flats taken after the flats

Here you can find some files, if you want to have a look: https://drive.google.com/drive/folders/ ... sp=sharing

• final_ST.jpg is the file just out of StarTools
• final_ST_GIMP.jpg is the file sharpened and hue-saturated using GIMP
• stacked_dss.FTS is the stacked file using DSS as per the workflow on startools.org
• stacked_astap.fits is the stacked file using ASTAP as per the workflow on startools.org
• a single raw file for each type of frame (light, dark, flat and flat dark)

ST workflow:

Code: Select all

autodev -> keep
bin -> 60% -> keep
crop -> keep
wipe -> do -> keep
autodev -> redo global stretch -> keep
contrast -> dark anomaly filters 3 -> do -> keep
Sharp -> next -> keep
Color -> dark saturation 3.10, saturation 240%, green bias reduce 1.98 -> keep
Life -> less=More -> do -> keep
Entropy -> Dark/Light 70%/30% -> do -> keep
Tracking off -> grain removal: grain size 2 pixels -> next

I know that for those target I should have used a modified DSLR, but I'm not gonna buy one because it's very likely I will buy an astro-dedicated camera in a not-so-far future.
I know also that I should have taken at least 3 times more data, but that was the only single clear night I had in a while (and probably the only one for still a while)

Now some questions for you:

1. are my calibration frames well taken? Or did I do something wrong with darks/flats/dark flats?
2. why do I have so many green pixel in my final result? Is it because I need way more signal?
3. why do I have this dense stars bloat in my final image? Is it because of the lens/too few signal/etc? I see online pictures with way less stars, how is it achievable without using software? Or is it just post-processing stuff?
4. can I add extra data next time I will have a clear night? If yes, is it gonna be a problem if I have to re-focus because in the meanwhile I will have used my lens for other stuff? Getting the same f-ratio and focal length is not a problem, but same focus is never gonna be possible.
5. with the data I have, how is my final result? Can it be improved? If yes, how?
6. any other feedback for me?

Thanks a lot guys!

[happy-kat]

What version of DSS and startools are you using?
Did you take any bias files?

[polslinux]

What version of DSS and startools are you using?
Did you take any bias files?

DSS 4.2.5 and ST 1.6.400MR1.
No, I didn't take any bias because I've read that they're not really useful if flats and dark flats are well taken.

[happy-kat]

With a DSLR darks can be found to add noise, but bias are ok and help with DSLR. Your camera mileage may vary.
Your green is natural. The bayer matrix has 2 green pixels, 1 red, 1 blue.
If you are ensuring no white balance in DSS settings then in startools in the colour module select the matric for your camera.
Hope that helps

[admin]

Some quick observations;

• The ASTAP stack appears to have been color balanced and there appears to be a dust donut remaining.
• The DSS stack does not appear to have been color balanced and would make for a better starting point.
• Your calibration frames do not appear to catch all the uneven lighting (and one notable smudge/dust speck remains at 9 o'clock).
• Your lens suffers from chromatic aberration. You will want to use less aggressive saturation for the highlights, use the Repair Highlights parameter in the Color module and/or use the Filter module's Fringe Killer algorithm to get rid of purple fringing.
• Overall, I think you did a nice job with the dataset at hand!

[polslinux]

Some quick observations;

• The ASTAP stack appears to have been color balanced and there appears to be a dust donut remaining.

Hmm, that's weird. I followed exactly what I did the other time.
I have tried again, this time by modifying a setting. Could you please check whether this ASTAP stack is good?

Same link as the first post, but there's a new file called stacked_astap_NEW.fits

Also, how do you determine if a stack has been color corrected? Could you tell me please? So next time I'll be able to evaluate it myself

[admin]

Hmm, that's weird. I followed exactly what I did the other time.
I have tried again, this time by modifying a setting. Could you please check whether this ASTAP stack is good?

Yep, that's better!

Also, how do you determine if a stack has been color corrected? Could you tell me please? So next time I'll be able to evaluate it myself

The bias color (when opened with the first option) was red, which is a tell-tale sign of balance correction. A non-whitebalanced dataset from a DSLR or OSC will never have a red bias, but almost always a green, teal or (in rarer cases) yellow bias.

[polslinux]

Hmm, that's weird. I followed exactly what I did the other time.
I have tried again, this time by modifying a setting. Could you please check whether this ASTAP stack is good?

Yep, that's better!

[/quote]

If you want to update the how-to on startools.org, this is what I did extra compared to last time: I disabled "Colour Smooth":

[admin]

Much appreciated! I updated the section about ASTAP. Thank you!