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Subframe pre selection [Deep Sky] Processing techniques · enta · ... · 31 · 1467 · 1

This topic contains a poll.
How do you pre select your subs for WBPP
I have trust issues and exclusively use the best subs
I use as much subs as possible and only exclude the bad ones
I don't, pixinsight is smarter than humans
MikeHuerto 2.39
Mike Dobres
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I blink for satellites and then use sub frameselector in PI based on FWHM and number of stars - set to limits below and above the light grey area respectively.

As the author of this video explain, at about 6:20, wbpp already selects for PSF and SNR.   https://youtu.be/mLmtVcgaQZo?si=dyyYIEfOIW6mhtaC




I first used SBS when I had imaged over 30 hrs on CTB1 and wanted a way to select for sharper structure of the nebulosity - so I selected the best 450 of about 700 based on FWHM and star count - which corresponded to limits below and above the dark grey area.  I figured sharper stars would translate to sharper non stellar. Yes,  I threw out a lot, but after running WBPP at default settings I could easily see the improvement in the sharpness of the nebulosity, especially for the OIII signal, and I still had 23 hrs🤷‍♂️. 

For more recent wide field shots using a Samyang 135, I just used Blink in PI. In this case I shot the nebulosity at F2 and the stars at F11. Works great - pinpoint stars throughtout the FOV.

ps- the screenshot is from the video - not my data.
Edited ...
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kdzuin 0.90
Konstantin Dzuin
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Adam Block has an amazing video explaining different measuring tools within PixInsight, and in different videos – using NSG. 

I’d like to point out, that different scenarios require different set of tools. There is a huge difference in measurements between PSF Signal Weight and PSF Scale SNR. Take a look at what you want to achieve, and approach things in that way. 

The easiest way to assess the difference for your particular setup and target – integrate using different weighing methods. 

In my case, of rather undersampled data, I tend to stick to PSF Scale SNR method. The lower limit for the weight may vary depending on the number of sub exposures, but usually I go with values around 0.4 to 0.5. I really don’t want to keep frames that are two times or so worse than the reference frame. 

The PSF Scale SNR metric is not available in Subframe Selector from the very beginning (as the data required is not calculated during calibration), you need to run the Local Normalisation first, and then you can use the Subframe Selector and compare the weights for both main weighing methods and decide for yourself, which one represents the “quality” to your liking. 

Beat regards,
Konstantin
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Semper_Iuvenis 3.10
Monty Chandler
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I don't use the wbpp script either.   It's a bad assumption..  However,  SFS does a great job of identifying anomalies within the dataset.
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CCDnOES 8.34
Bill McLaughlin
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I do four steps:

1) Blink for obvious crap frames. Usually very few in my location and setup but typically high clouds fuzz or giant airplane/satellite streaks.
2) Subframe Select to locate and delete frames with poorer S/N and/or  FWHM not up to my requirements.
3) Manually calibrate and register - WBPP is too much of a black box for my taste and saves almost no time compared to my "manual" calibration.
4) Normalize Scale Gradient to combine.
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birelian 5.49
Guiem Kimi
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Ken Mascola:
Guiem Kimi:
I use NINA and then export the image history as a CSV file.

I used to check the CSV and discard subs based on:

- Total RMS.
- Eccentricity.
- Median value compared to the best frame.
- Number of stars ratio compared to the best frame.
- FWHM

.....

I know there are tools for doing that, but I just wanted to build something by myself just for fun.

I was planning to upload the script to Github under GPL license. So, if anyone wants to try it, no problem about that.

Guiem.

Hello Guiem...
Looking to do something similar. Would like to preview and autoreject subs as well as factor which registration and stacking script to best use based on these type os parameter. I only image small galaxies  and want more consistent image quality. Interested in seeing what you have put together if you are willing to share. Did you post on Github... All for fun and enjoyment....

Ken

Hi Ken,

Of course. You can find it in GitHub. It's quite simple and for sure there may be better ways, but it works like a charm for my workflow.

CS.
Guiem.
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Glabella 0.00
Ken Mascola
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Guiem Kimi:
Ken Mascola:
Hello Guiem...

Hi Ken,

Of course. You can find it in GitHub. It's quite simple and for sure there may be better ways, but it works like a charm for my workflow.

CS.
Guiem.

Thanks. I had misread your original post and thought you had analysed the subs but now realize you are using the output in a csv file via nina.  Great approach. Personally I am looking at automating the complete process and via python doing all the analysis.. slow and steady one by one… I am in no rush. Now just trying to define how I want to determine  as S/N and then work through that. In any event there are many rabbit holes to traverse..that’s for sure.
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birelian 5.49
Guiem Kimi
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Ken Mascola:
Guiem Kimi:
Ken Mascola:
Hello Guiem...

Hi Ken,

Of course. You can find it in GitHub. It's quite simple and for sure there may be better ways, but it works like a charm for my workflow.

CS.
Guiem.

Thanks. I had misread your original post and thought you had analysed the subs but now realize you are using the output in a csv file via nina.  Great approach. Personally I am looking at automating the complete process and via python doing all the analysis.. slow and steady one by one… I am in no rush. Now just trying to define how I want to determine  as S/N and then work through that. In any event there are many rabbit holes to traverse..that’s for sure.

No worries @Ken Mascola. I think your approach is the way to go. No need of export files and no coupling with software acquisition. It is where I want to go when I have time.

I hope you can traverse all the rabbit holes!

CS.
Guiem.
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