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9 July 2020 - APP 1.082 has been released which contains one important bug fix. 1.082 has full Fujifilm RAF support, so that includes SuperCCD & X-Trans camera's 🙂 !

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[Solved] Bad Pixel Map  

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(@didi_sangye)
White Dwarf Customer
Joined: 8 months ago
Posts: 13
May 21, 2020 19:30  

Hello everyone,

i purchased a new OSC-Camera (ASI071MC_Pro) and as recommended i started to do a good bad pixel map by taking 100 dark-frames (600sec, gain 0, -5°c) and 100 flats.

But i'm quite shocked about the result:

image

26,92% of BAD pixels. In the video from sarah i saw here values: 3,325 %!!!

am ii doing something wrong or is this a bad camera!!??


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(@ippiu)
Main Sequence Star Customer
Joined: 1 year ago
Posts: 42
May 21, 2020 20:23  

it's normal.

As it usually happens in ALL OSC CMOS cameras, gain 0 is noiser than all other gains. Don't use gain 0.

It's common to use UNITY GAIN: for your camera it is 90 as you can see here:


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(@didi_sangye)
White Dwarf Customer
Joined: 8 months ago
Posts: 13
May 21, 2020 23:31  

@ippiu

thank you for your advice:-)

i will try it again using gain 90!


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(@didi_sangye)
White Dwarf Customer
Joined: 8 months ago
Posts: 13
May 22, 2020 11:14  

I found out, that this has nothing to do with the GAIN-value; nearly the same values with Darks Gain 90!! And i also watched a youtube-video from robin glover (

) saying that the 'unity-gain-concept' is a irrelevant one; so i decided to use gain 0.

And also see this post from mabula:

https://www.astropixelprocessor.com/community/tutorials-workflows/a-dslr-data-calibration-workflow-by-mabula/#post-8676

Posted by: @mabula-admin

No, the Bad Pixel Map is NOT ISO and exposure dependent. You can make a Bad Pixel Map using any ISO and exposure time and use it on data which have other ISO and exposure times. Just make one Bad Pixel Map using a set of darks with exposure times of several minutes (the longer the better) and an arbitrary ISO value. And the flats used in the BPM creation can have a different ISO and exposure time then those darks, no problem 😉

 

In both cases (gain 0 / gain 90) i used the values for 'bad kappa' and 'cold pixel percentage' that mabula is using in the example of his post: https://www.astropixelprocessor.com/community/tutorials-workflows/creating-a-bad-pixel-map/

As i don't really understand what this values are doing, for me is was helpful to use these values (cold pixels 50% and hot pixels kappa 2.5)

 

Today I restarted the whole thing, but this time i didn't change the default values suggested in the actual version of APP: cold pixels 25% and hot pixels kappa 3.0 and the result is a completely different one:

image

And now i'm completely confused; the idea is to create a very good BPM once in a year (as suggested by mabula)

And now i have this 2 completely different versions; and on top the second one looks quite strange to me compared to the first one (see above)

Maybe this is due to my self made 'flat-box' (a led light-pad from agptek)!?

 

So which one should i use for the calibration of my flats and my lights??

Would be very nice if someone could help me to clarify my confusions and tell me what to do; thanks in advance!

 


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(@didi_sangye)
White Dwarf Customer
Joined: 8 months ago
Posts: 13
May 22, 2020 15:41  

Hey Mabula!

If a BPM is needed to do the best calibration; waht's the way to create a really good BPM?

Is it to find the best values or to detect a realistic number of so called 'bad pixels' and to apply this to the calibration of the flats and lights, or is it to optimise certain values?

Because when i play aorund a little bit with 'hot pixels kappa' and 'cold pixels percentage' i can find a combination with a maxium of 'number of linear pixels' and a minimum of 'number of bad pixels' ()

image

but again; what's really the goal to strive for?

please help


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1913
May 24, 2020 12:49  

Hi @didi_sangye,

edit:sorry, I see you already tried gain 90. Could you upload a few of the darks just for me to check?

Please upload like 5 to our server and login with username/password: appuser

Create a directory with "didi_sangye-BPM-issue" and upload there. Thank you!


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(@didi_sangye)
White Dwarf Customer
Joined: 8 months ago
Posts: 13
May 24, 2020 13:54  

Hi Vincent,

Thank you for your answer; i think it must sound a little bit confusing for you!!

But meanwhile i found in another post ("ASI071MC processing") that it is needed to enable "force CFA" for these frames in 0) RAW/FITS!!

Coming from DLSR -and as a beginner- it was new for me or to be precise in the APP Tipp-Text to this topic it says: "Enable this if the frames are monochrome Bayer CFA frames..."; and i thought that the frames of a OSC-Camera are NOT monochrome because it is a One-Shot-COLOR camera (like DSLR)!!??

So again it's the same topic of a 'missing documentation/manual of the ACTUAL APP-Version' 🙁

But now i tried it again with this option enabled and i managed to get a 'better' or maybe 'correct' BPM and to find out the 'Hot-Pixels-Kappa-Value' that corrects all bad pixels -as it is mentioned in the post 'Creating a BPM' (from Mabula but from 2017!!)- means it stays the same value from there on (i hope that's the correct way); the cold pixel percentage is always 0!

 

Kind regards

Didi_Sangye

 

 

 


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