New to ST and first light on M31 (and first ever). Help with processing.

Questions and answers about processing in StarTools and how to accomplish certain tasks.
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polslinux
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New to ST and first light on M31 (and first ever). Help with processing.

Post by polslinux »

Hello all,
I recently started this new hobby, and finally yesterday I captured my first DSO :mrgreen:
I chose M31, because it's a bright and easy target for a beginner.

As this was my first try ever, I wanted to keep things simple, so I captured only lights (had to deal with the all polar alignment, focus, etc).

Tech stuff:
iOptron SkyGuider Pro
Nikon D7500
Tamron 150-600 g2 @ 180mm f/5
98 subs, 30 sec each
ISO 400
no darks, flats, biases

What I did with Startools:
* Stack all files with DSS using these options: https://www.startools.org/links--tutori ... r-settings
* Export to 32 bit integer TIFF
* Open file in ST
* Choose "Linear, from OSC/DSLR with Bayer matrix and not white balanced"
* follow all steps https://www.startools.org/modules/intro ... /workflows
-> autodev, keep
-> bin, 50%, keep
-> crop, center object, keep
-> wipe, do, keep
-> autodev, redo global, keep
-> contrast, do, keep
-> color, keep

DSS stacked TIFF using ST instructions: https://drive.google.com/file/d/1Eyoqdt ... sp=sharing

Sequator stacked TIFF: https://drive.google.com/file/d/1y0vAPa ... sp=sharing

NEF of one light frame: https://drive.google.com/file/d/1NC7R2q ... sp=sharing

As you can see from the attached images, I get two different results between ST and PI.

As I'm still evaluating the two software, I'd like to understand what I did wrong with ST.

Thanks
Attachments
M31 processed with Startools
M31 processed with Startools
m31st.jpg (393.07 KiB) Viewed 552 times
M31 processed with PI
M31 processed with PI
m31pi.jpeg (314.71 KiB) Viewed 552 times
happy-kat
Posts: 261
Joined: Sun Feb 01, 2015 11:31 am

Re: New to ST and first light on M31 (and first ever). Help with processing.

Post by happy-kat »

Hi
Thinking about DSS, what version of DSS are you using please?
StarTools what version are you using?

I ask because it is easier to relate what I see if I know the versions before commenting.
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admin
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Re: New to ST and first light on M31 (and first ever). Help with processing.

Post by admin »

polslinux wrote: Fri Sep 11, 2020 2:39 pm Hello all,
Hi and welcome to the forums (and the hobby!)
As this was my first try ever, I wanted to keep things simple, so I captured only lights (had to deal with the all polar alignment, focus, etc).
The problem is that not acquiring flats is a false economy; as you're finding out they make your life a lot harder - not easier!

Because you did not calibrate with flats you now have to try to process out gradients and separate the galaxy from the murk. This is more difficult (and will always yield suboptimal results) than just being able to "trust" your data as it came out of the stacker.

Your default workflow is sound though (if your dataset had been calibrated with flats) and you've brought out all the interesting coloring.

Due to the strong gradients and uneven lighting, you will have to help Wipe a bit more with figuring out what is gradient and what is signal.

To do this, first roughly mask out (you can see how embarrassingly rough I drew the shape below :oops: ) the area that is definitely signal (or definitely not signal in the case of artefacts) and, hence, should be off-limits for Wipe to look for an interstellar background. I use the lasso tool for this.
StarTools_205.jpg
StarTools_205.jpg (148.49 KiB) Viewed 537 times
Then, back in Wipe, I used the Vignetting preset and further increased the Aggressiveness until most of the uneven background disappeared. I'm say "most" here, as Wipe will relentlessly keep showing your how "bad" you background is through its courtesy AutoDev for diagnostics purposes; your are of course not obliged to stretch as hard as the courtesy AutoDev is doing here on purpose;
StarTools_204.jpg
StarTools_204.jpg (408.03 KiB) Viewed 537 times
After "keeping" the result, you do an AutoDev once more - this time for your real/final globl stretch using the cleaned up data. As with all images that contain an interesting object on an otherwise uninteresting dark/noisy background, be sure to specify a Region of Interest for AutoDev to optimize for;
StarTools_206.jpg
StarTools_206.jpg (184.56 KiB) Viewed 537 times
Do whatever else you fancy doing to the image (with low signal, you will notice that StarTools becomes much more careful with how/where it applies enhancements, as everything is constantly balanced against how badly noise grain will increase - it is much harder to "overcook" images in StarTools because of this).

If you now run the Color module you should see the same roughly the same coloring you already accomplished. However sanity-checking the coloring with the MaxRGB mode reveals that the galaxy's core is too green-dominant (it should be yellow due to gas depletion leaving only older stars). Keep increasing Green Bias Reduce until the core no longer is. Once you're satisfied your color balance is correct you can decide to set Cap Green to 100% to kill any left over green noise. If you think your data can handle it, you can decide to introduce a little more saturation in the darker parts.

All in all what you want to see is a yellow core, a bluer outer rim, red/brown dust lanes, a good random distribution of foreground star temperatures. E.g. something like this;
StarTools_207.jpg
StarTools_207.jpg (292.95 KiB) Viewed 537 times
Turn off Tracking, avail of the targeted data mined noise reduction to your taste, and you'll end up with something like this;
m31_32bit_DSS.jpg
m31_32bit_DSS.jpg (372.45 KiB) Viewed 537 times
Priority #1 should be flats. From there on it's just a matter of collecting more data and you're on well on your way!

Hope this helps.
Ivo Jager
StarTools creator and astronomy enthusiast
polslinux
Posts: 13
Joined: Fri Sep 11, 2020 11:55 am
Location: Italy
Contact:

Re: New to ST and first light on M31 (and first ever). Help with processing.

Post by polslinux »

happy-kat wrote: Fri Sep 11, 2020 7:05 pm Hi
Thinking about DSS, what version of DSS are you using please?
StarTools what version are you using?

I ask because it is easier to relate what I see if I know the versions before commenting.
I'm using DSS 4.2.3 and ST 1.6.400M1
polslinux
Posts: 13
Joined: Fri Sep 11, 2020 11:55 am
Location: Italy
Contact:

Re: New to ST and first light on M31 (and first ever). Help with processing.

Post by polslinux »

admin wrote: Sat Sep 12, 2020 3:50 am Hi and welcome to the forums (and the hobby!)
Thanks a lot :D
admin wrote: Sat Sep 12, 2020 3:50 am Because you did not calibrate with flats you now have to try to process out gradients and separate the galaxy from the murk. This is more difficult (and will always yield suboptimal results) than just being able to "trust" your data as it came out of the stacker.
I've learned it the hard way :mrgreen: next clear night I will for sure take all calibration frames!
admin wrote: Sat Sep 12, 2020 3:50 am Your default workflow is sound though (if your dataset had been calibrated with flats) and you've brought out all the interesting coloring.

Due to the strong gradients and uneven lighting, you will have to help Wipe a bit more with figuring out what is gradient and what is signal.

To do this...
Thanks a lot, that was super helpful! I was able to get a similar result :)
I definitively need to read the whole ST manual, because I need to really understand what and why I'm doing these steps :thumbsup:
happy-kat
Posts: 261
Joined: Sun Feb 01, 2015 11:31 am

Re: New to ST and first light on M31 (and first ever). Help with processing.

Post by happy-kat »

with that DSS then you could amend the settings to select No white balance, then in StarTools you can select the matrix for your camera which would manage the green for you with little to no adjustment needed
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