Flat field critical...
 
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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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Flat field critical warning for wrong reason  

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(@astrogee)
Red Giant Customer
Joined: 2 years ago
Posts: 96
October 21, 2019 16:24  

I've been getting this warning for some time but seems to have no effect. But now that I've update to 1.075 and I'm processing directly from DNG files, I thought I would report it. Please see attached screen capture: 

Screen Shot 2019 10 21 at 8.49.45 AM

 

The message is incorrect because all files are ISO 1600 so this message should not appear. Please see attached file showing file ISO:

Screen Shot 2019 10 21 at 10.21.29 AM

Assuredly the lights are also ISO 1600


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(@maaxx)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 4
October 22, 2019 02:37  

That's because you didn't use Darks I believe..


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1892
October 22, 2019 10:00  

It doesn't have anything to do with the ISO really (as in those of the lights) it has to do with needing a bias, required to normalize the flats that needs to be of the same ISO as the lights. Looking at the files it does seem you successfully created a masterbias and masterflat, those were created in this same session? What is your workflow exactly, maybe that sheds some light on it.


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(@astrogee)
Red Giant Customer
Joined: 2 years ago
Posts: 96
October 22, 2019 14:25  

My workflow is very simple now thanks to the DNG support! Thanks again for that!

I leave all settings in the default position and load light, flat and then bias frames - I have yet to do darks but will be trying that today.

Then simply click "Create masters and assign to lights" in tab 2.

Then after the MB is created I see that critical warning. I click OK and processing continues.

Then the MF is created and everything seems to be ok. Just that I'm getting the warning unnecessarily.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1892
October 22, 2019 19:31  

That indeed is strange, I'll tag Mabula @mabula-admin so he can have a look at it.


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(@maaxx)
Molecular Cloud Customer
Joined: 1 year ago
Posts: 4
October 23, 2019 04:04  

APP always issues a warning if flats are used without either bias or dark or both.

 


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(@mabula-admin)
Quasar Admin
Joined: 3 years ago
Posts: 2451
October 23, 2019 12:28  

Hi @astrogee, @maaxx & @vincent-mod,

APP always issues a warning if flats are used without either bias or dark or both.

Indeed, for proper flat-field calibration the flats need to be calibrated with either bias, darkflats or both.

It doesn't have anything to do with the ISO really (as in those of the lights) it has to do with needing a bias, required to normalize the flats that needs to be of the same ISO as the lights.

Now, this is not entirely correct. To properly created a masterbias to correct light frames. The flats need to be corrected with a masterbias that has the same iso/gain as the flats.  If the lights have a different ISO/gain value compared to the flats, then you would need 2 masterbiases of the respective ISO/gain values. That is the correct way to calibrate data. Flats can have a different iso/gain value compared to the lights, that is no problem with the camera's these days. (If you have a VERY old camera that does not behave linearly, well then please use the same iso to prevent problems.)

Now since a Masterbias has been created that has the same pixel dimensions as the flats, the warning should not be there. Since APP issues a warning here, it seems that the flats and bias are not matched so I suspect the flat-field calibration is not working as it is supposed to be here.

@astrogee, can you upload a couple of bias and flats and lights (maybe 3-5 of each ?) so I can check what is happening and make sure it works correctly?

https://ariesprodstor.astropixelprocessor.com:7001/

login and password: appuser

Create a folder with your name and let me know once uploaded, then I will have a look as soon as possible.

Kind regards,

Mabula


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(@astrogee)
Red Giant Customer
Joined: 2 years ago
Posts: 96
October 23, 2019 13:53  

Hi Mabula, Thanks for responding. I'm having trouble with the security on the link you gave me so I'll have to get back to you a little later. Maybe I should use an FTP client? Had one somewhere but can't find it right now :-s


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(@itarchitectkev)
Red Giant Customer
Joined: 2 years ago
Posts: 79
October 23, 2019 17:16  

I had this for my process I just did now. I have:

Lights (Gain=200, Exposure =300s, Temp -20C)

Darks (Gain=200, Exposure = 300s, Temp -20C)

Flats + DarkFlats of same exposure lengths.

No Bias

I got the warning up during Calibration. I cleared it. I processed again after thinking I missed something and then didn't get the error. I was doing multi-session + multi-filter. As far as I could see I checked all boxes yet APP complained.


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(@astrogee)
Red Giant Customer
Joined: 2 years ago
Posts: 96
October 24, 2019 00:17  
Posted by: @mabula-admin

Hi @astrogee, @maaxx & @vincent-mod,

APP always issues a warning if flats are used without either bias or dark or both.

Indeed, for proper flat-field calibration the flats need to be calibrated with either bias, darkflats or both.

It doesn't have anything to do with the ISO really (as in those of the lights) it has to do with needing a bias, required to normalize the flats that needs to be of the same ISO as the lights.

Now, this is not entirely correct. To properly created a masterbias to correct light frames. The flats need to be corrected with a masterbias that has the same iso/gain as the flats.  If the lights have a different ISO/gain value compared to the flats, then you would need 2 masterbiases of the respective ISO/gain values. That is the correct way to calibrate data. Flats can have a different iso/gain value compared to the lights, that is no problem with the camera's these days. (If you have a VERY old camera that does not behave linearly, well then please use the same iso to prevent problems.)

Now since a Masterbias has been created that has the same pixel dimensions as the flats, the warning should not be there. Since APP issues a warning here, it seems that the flats and bias are not matched so I suspect the flat-field calibration is not working as it is supposed to be here.

@astrogee, can you upload a couple of bias and flats and lights (maybe 3-5 of each ?) so I can check what is happening and make sure it works correctly?

https://ariesprodstor.astropixelprocessor.com:7001/

login and password: appuser

Create a folder with your name and let me know once uploaded, then I will have a look as soon as possible.

Kind regards,

Mabula

Hi Mabula,

I'm having trouble uploading. I can't get proper access. Don't I need the home directory for appuser? I get this message:

Screen Shot 2019 10 23 at 6.16.19 PM
Screen Shot 2019 10 23 at 7.24.57 PM

 


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(@astrogee)
Red Giant Customer
Joined: 2 years ago
Posts: 96
October 24, 2019 01:53  

I put the files in a dropbox here: https://www.dropbox.com/sh/zg8ilzq5tz21bmz/AADVswOT8MOWsvx6gIKiMAgIa?dl=0

Thanks


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1892
October 28, 2019 12:28  

Thank you, sorry for the delay, I've been away for a bit as I'm moving (yet again). The server doesn't have a certificate indeed, this seems to be fine for most browsers that only warn about it, but some might have issues. Mabula might look into getting a certificate, but just for sharing data it seems a bit unnecessary maybe.

I'll download the files and have a go myself.


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(@vincent-mod)
Quasar Admin
Joined: 3 years ago
Posts: 1892
November 1, 2019 12:33  

So I tested the files and I first created the master frames which worked fine without warning. Integration completed as well without warning..


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