¿Do you use dark-flats in WBPP?

15 replies525 views
Daniel Arenas avatar
Hi,

I’m taking lights, darks, bias, flats and dark-flats but when stacking with WBPP I don’t know how to use de dark-flats. 
Maybe I have to upload them with the other darks and WBPP will understand that they will be used to callibrate flats?

Many thanks and clear skies!
Jérémie avatar
Yes, I use both.
The way to do it is : upload all your Darks in the Darks tab, then on the Calibration tab, you can select each serie of images you imported, and on the right side let Pixinsight choose automatically its Darks, or select the serie manually.
Concise
Bruce Donzanti avatar
Dark flats get loaded with the darks in WBPP.  However, you don’t need both bias frames and dark flat frames.  Use one or the other.  I never heard of using both.
Helpful Concise
Jérémie avatar
Here below you see that PI can automatically check  that your Darks have different exposition time

Bruce Donzanti avatar
Jérémie:
Yes, I use both.
The way to do it is : upload all your Darks in the Darks tab, then on the Calibration tab, you can select each serie of images you imported, and on the right side let Pixinsight choose automatically its Darks, or select the serie manually.

Interesting, why use both bias and dark flats?
Jérémie avatar
Here you see that selecting the Flats, I can choose which Darks serie to use. You can do the same with the Lights. That can be useful if you integrate Lights coming from various nights and with various exposure time (Darks would be different).

Jérémie avatar
Bruce Donzanti:
Jérémie:
Yes, I use both.
The way to do it is : upload all your Darks in the Darks tab, then on the Calibration tab, you can select each serie of images you imported, and on the right side let Pixinsight choose automatically its Darks, or select the serie manually.

Interesting, why use both bias and dark flats?

I don't take Bias.

I use Darks for everything : Bias is included in the Darks, so when you subtract the Darks, Bias is automatically subtracted as well...
When Flats have short exposure time, well, Bias or Dark is the same

The only drawback of my method is that you cannot "tweak' the Darks. But I wouldn't do it in any case so....

I think I remember that not using bias was the prefered / recomended way of doing things by PI. I would have to check, but there has been lots of discussions on that few years ago.
Manfred Fröhlich avatar
Hello Daniel,

I use only Darks with the same flat exposer time.

At the following link there is a good discription why this works wthout problem.

Look the text from  Frank and Gerd
https://www.astrotreff.de/forum/index.php?thread/232976-was-sind-flat-dark-frames-fragen-zu-regim/

Cs Mani
Sorry for my uncorrect english !)
Bruce Donzanti avatar
Jérémie:
Bruce Donzanti:
Jérémie:
Yes, I use both.
The way to do it is : upload all your Darks in the Darks tab, then on the Calibration tab, you can select each serie of images you imported, and on the right side let Pixinsight choose automatically its Darks, or select the serie manually.

Interesting, why use both bias and dark flats?

I don't take Bias.

I use Darks for everything : Bias is included in the Darks, so when you subtract the Darks, Bias is automatically subtracted as well...
When Flats have short exposure time, well, Bias or Dark is the same

The only drawback of my method is that you cannot "tweak' the Darks. But I wouldn't do it in any case so....

I think I remember that not using bias was the prefered / recomended way of doing things by PI. I would have to check, but there has been lots of discussions on that few years ago.

Ok- I misunderstood.  I thought you were taking both.  I believe you are correct about dark flats in PI being preferred in PI, especially with the CMOS cameras.
Daniel Arenas avatar
Thank you @Jérémie 

Bruce Donzanti:
Jérémie:
Yes, I use both.
The way to do it is : upload all your Darks in the Darks tab, then on the Calibration tab, you can select each serie of images you imported, and on the right side let Pixinsight choose automatically its Darks, or select the serie manually.

Interesting, why use both bias and dark flats?

Why not @Bruce Donzanti ?

If I’m not wrong bias are used to callibrate electronical noise. Darks are used to callibrate lights with flats but if flats exposures are more that one second we’ll need dark-flats to callibrate them. 

Am I making any mistake?

Kind regards
Jérémie avatar
Bruce Donzanti:
Jérémie:
Bruce Donzanti:
Jérémie:
Yes, I use both.
The way to do it is : upload all your Darks in the Darks tab, then on the Calibration tab, you can select each serie of images you imported, and on the right side let Pixinsight choose automatically its Darks, or select the serie manually.

Interesting, why use both bias and dark flats?

I don't take Bias.

I use Darks for everything : Bias is included in the Darks, so when you subtract the Darks, Bias is automatically subtracted as well...
When Flats have short exposure time, well, Bias or Dark is the same

The only drawback of my method is that you cannot "tweak' the Darks. But I wouldn't do it in any case so....

I think I remember that not using bias was the prefered / recomended way of doing things by PI. I would have to check, but there has been lots of discussions on that few years ago.

Ok- I misunderstood.  I thought you were taking both.  I believe you are correct about dark flats in PI being preferred in PI, especially with the CMOS cameras.

Well, reading everything again, I misunderstood the initial question, hence my answer that was indeed not very clear 
Rob Kiefer avatar
Hi Daniel, I highly recommend Adam Block youtube tutorials (The definitive guide to WBPP). Very detailed and all questions will be answered.
Tom Boyd avatar
Yes. I use a master dark and dark flats, no bias frames. Simply load your master dark and your dark flats and let WBPP do the rest.
kuechlew avatar
Daniel Arenas:
Hi,

I’m taking lights, darks, bias, flats and dark-flats but when stacking with WBPP I don’t know how to use de dark-flats. 
Maybe I have to upload them with the other darks and WBPP will understand that they will be used to callibrate flats?

Many thanks and clear skies!

Dark flats are darks with the exposure time of the flats. By default WBPP uses the exposure time to choose the proper darks for calibration. So it calibrates the flats with the darks with same exposure time.
When using darks you don't need bias frames because the darks contain the read noise too, so when subtracting the master dark from lights / flats you subtract the average read noise in the process.

Clear skies
Wolfgang
Helpful Concise
Daniel Arenas avatar
Rob Kiefer:
Hi Daniel, I highly recommend Adam Block youtube tutorials (The definitive guide to WBPP). Very detailed and all questions will be answered.

Yes I do that with subtitles cause english is not my native language and the speed of speaking is an issue on me.

Let me edit this message:

I was confused with the author, Adam has a great pronnounce accent and tempo. I’ll review those videos. 

Thanks! 🤗
Daniel Arenas avatar
Daniel Arenas:
Hi,

I’m taking lights, darks, bias, flats and dark-flats but when stacking with WBPP I don’t know how to use de dark-flats. 
Maybe I have to upload them with the other darks and WBPP will understand that they will be used to callibrate flats?

Many thanks and clear skies!

Dark flats are darks with the exposure time of the flats. By default WBPP uses the exposure time to choose the proper darks for calibration. So it calibrates the flats with the darks with same exposure time.
When using darks you don't need bias frames because the darks contain the read noise too, so when subtracting the master dark from lights / flats you subtract the average read noise in the process.

Clear skies
Wolfgang

Great @kuechlew !
That have a lot o sense 🙌
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