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[Sticky] A DSLR data calibration workflow by Mabula  

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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 2081
October 4, 2017 15:33  

Hi all,

This is a new video tutorial made possible by using data of Douglas Mason, thank you Douglas!

A DSLR data calibration workflow

Let me know if there are any questions 😉

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@frank_teunissen)
Hydrogen Atom Customer
Joined: 2 years ago
Posts: 1
February 19, 2018 18:00  

Hallo Mabula, zou het kunnen zijn dat er een foutje zit in deze video/handleiding?

Moet de iso waarde van de BIAS frames overeenkomen met de iso waarde van de DARK frames? Zo ja dan moet dus alle BIAS, DARK, FLAT en de LIGHT frames dezelfde iso waarde hebben. In de video wordt er mogelijk een onderscheid gemaakt: iso DARK = iso LIGHT en iso BIAS = iso FLAT (bij 1m:01s) . In het verhaal staat echter: iso DARK = iso FLAT. Wat is de juiste setting?

Mvg Frank  Teunissen

edit: translation by Mabula:

Does the ISO value of Bias frames need to be the same as the ISO value of dark frames? If that's the case, then there might be an error in your DSLR data calibration video tutorial. What's the correct value?

 


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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 2081
March 4, 2018 18:23  

Hi Frank @frank_teunissen,

No there is no error there. Let me explain:

It all depends on what you are trying to calibrate with the bias frames.

If you use bias frames to calibrate flats, the bias frames need to have the same ISO value as the flats.

If you use bias frames to calibrate lights, the bias frames need to have the same ISO values as the lights.

( and... If you use bias frames to calibrate darks, the bias frames need to have the same ISO as the darks.)

Other applications are less strict about this and fundamentally that's not a good thing in my opinion. If your Bias frames have a clear noise pattern to them (like horizontal or vertical stripes) then not following these rules will actually give you worse calibration. Currently APP forces these rules which confuses some users since other applications are not so strict. I do intend to make this easier in a next APP version though. The whole calibration engine will be upgraded soon.

Kind regards,

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@hans_van_overzee)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
March 5, 2018 21:16  

Ha Mabula I have got a question.

For making  the master flat for instance an ISO for the flats of 400 is used.

As I understand it the Bias has to be also ISO 400. Both frames got to have  the same exposure time.

What about the bad pixel map used in this case has it also to be made of frames from darks and flats of ISO 400 with the same exposure time ?

 

If the lights have an other exposure time  and ISO for instance 800 the masterdark has to be made with the same exposure time and the ISO as the lights this is clear.

What about the bad pixel map in this case?

Have we got to make a second bad pixel map existing out of flats and darks with the same exposure time and ISO as the Lights and darks in this case?

 


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(@mabula-admin)
Quasar Admin
Joined: 2 years ago
Posts: 2081
March 21, 2018 12:44  
Posted by: Hans van Overzee

Ha Mabula I have got a question.

For making  the master flat for instance an ISO for the flats of 400 is used.

As I understand it the Bias has to be also ISO 400. Both frames got to have  the same exposure time.

What about the bad pixel map used in this case has it also to be made of frames from darks and flats of ISO 400 with the same exposure time ?

 

If the lights have an other exposure time  and ISO for instance 800 the masterdark has to be made with the same exposure time and the ISO as the lights this is clear.

What about the bad pixel map in this case?

Have we got to make a second bad pixel map existing out of flats and darks with the same exposure time and ISO as the Lights and darks in this case?

 

Hi Hans @hans_van_overzee,

As I understand it the Bias has to be also ISO 400. Both frames got to have the same exposure time.

Yes, If the flats are ISO400, then the Bias for the flats need to be ISO400, if you use darkflats for the flats, then they need to have the same ISO and exposure as the flats.

What about the bad pixel map used in this case has it also to be made of frames from darks and flats of ISO 400 with the same exposure time ?

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 😉

Have we got to make a second bad pixel map existing out of flats and darks with the same exposure time and ISO as the Lights and darks in this case?

So no, just make 1 BPM and use it on all Lights and Flats that you have 😉

Kind regards,

Mabula

Main developer of Astro Pixel Processor and owner of Aries Productions


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(@hans_van_overzee)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
March 21, 2018 14:26  

Thanks Mabula for this clear explanation

Cheers,

Hans 


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(@hans_van_overzee)
Main Sequence Star Customer
Joined: 2 years ago
Posts: 26
March 21, 2018 14:27  

Thanks Mabula for this clear explanation

Cheers,

Hans 


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