Beginner needs help processing M35 DSLR widefield

[dermarkus]

Hello,

I´m a beginner by all measures when it comes to astronomical image processing. That is why I
searched for a software that might give me reasonable results without too much hassle. Currently
I am evaluating Startools, but unfortunately I am not able to get any useful results.

I read through many posts in this forum and tried to follow the "standard" workflow of

- AutoDev
- Wipe
- AutoDev
- Contrast, Sharp, HDR etc.
- De-Noise

But I always end up with very noisy/grainy images that are not comparable to the results
that I can produce using e.g. Astroart by just tweaking the histogram.

Maybe someone can take a look at my DSS stacked image - M35 widefield 60 x 30sec unguided,
not dithered, no flats, no darks - and help me finding a workflow to get a decent result that
is comparable to what I can have by tweaking the histogram.

I can share the stacked image via Dropbox if needed.

Thanks for reading
Markus

[admin]

Hi Markus,

Happy to have a look if you'd like to share the data!

[dermarkus]

Hi Ivo,

you can download the DSS stack here:

https://www.dropbox.com/s/595i2vddudvbi ... 1.fts?dl=0

Thanks
Markus

[admin]

Hi Markus,

I had a look at your data.
The vignetting is rather extreme, which makes it really hard for StarTools to pick detail and discern between nebulosity and gradient. This doesn't mean StarTools can't do anyhting with your data, it just means it's much harder, since StarTools various analysis tools are having a harder time figuring out what'a going on and thus have a harder time coming up with reasonable defaults; more tweaking is needed. Conversely, you'll find that, with better calibrated data your workflow will be much shorter, consistent and very close to the 'standard' workflow which you already tried.

If you take anything away from this, it should be this; whichever software you decide to go with, you absolutely need to take flats!

All that said, you definitely have some objects in there (result below).

--- AutoDev
To see what we got.
We can see some small stacking artifacts, no clear cores to the stars, heavy oversampling, severe vignetting, severe bias/light pollution.
--- Bin
To reduce noise and make use of oversampling.
Parameter [Scale] set to [(scale/noise reduction 35.38%)/(798.89%)/(+3.00 bits)]
--- Crop
To get rid of stacking artifacts.
Parameter [X1] set to [19 pixels]
Parameter [Y1] set to [11 pixels]
Parameter [X2] set to [1503 pixels (-14)]
Parameter [Y2] set to [998 pixels (-12)]
--- Wipe
Very, very tricky gradient.
Used Vignetting preset with the following tweaks;
Parameter [Precision] set to [512 x 512 pixels]
Parameter [Dark Anomaly Filter] set to [2 pixels]
Parameter [Corner Aggressiveness] set to [98 %]
Parameter [Aggressiveness] set to [95 %]
--- Develop
Instead of AutoDev I had to resort to a manual develop (pretty rare). The trouble is that this is a widefield with much noise, so 1. there isn't really a 'region of interest' to focus on that has enough detail for AutoDev to lock on to and 2. there *is* much noise (and unevenness) for AutoDev to lock on to. It's a bad combo...
Parameter [Digital Development] set to [88.01 %]
Parameter [Dark Anomaly Filter] set to [11.3 pixels]
--- Life
Use Isolate preset to push back busy star field and focus the viewer's attention on the larger scale structures such as the DSOs, but also the star field's distribution (instead of just the stars).
--- Color
Used default color balance that StarTools came up with.
There is some spurious green color data that shouldn't be in there (caused by DSS color calibrating the image), so I chose to cap that green to 'yellow'.
Parameter [Cap Green] set to [To Yellow]
Parameter [Dark Saturation] set to [8.40]
Parameter [Bright Saturation] set to [Full]
Parameter [Saturation Amount] set to [200 %]
--- Wavelet De-Noise
Parameter [Grain Size] set to [23.9 pixels]

And that's it. Hope this helps! Again, though, keep in mind that with better calibrated, tracked and dithered data, you'll be "fighting" much less to get a good result. This will be true for any software, but particularly StarTools (which needs to be able to 'trust' the linear data to perform it's magic through data mining and signal evolution Tracking).

Autosave001(2).jpg (388.78 KiB) Viewed 6659 times

[Rowland]

Markus. This may be of assistance - I hope so...

Rowland

[dermarkus]

Hi Ivo,

thanks so much for taking the plunge.

I really do like what you have been able to make out of my DSS stack and I will follow it step by step to learn how to reproduce it.
How did you get rid of all those red hot pixels that are scattered all over the image ? When I try to get rid of them I always loose
all the signal in other details of the image as well.

In the meantime I have made some flats. Since the images were done with a telephoto lens and the camera position is very reproducible
when you connect it to the lens, they should be okay even though they were not done during the imaging session itself.

Thanks again and take care
Markus

[dermarkus]

Hi Robert,

thanks for pointing me to that thread. I will definitely have a look at it.

Thanks and take care
Markus