[Solved] Warning message when loading Flats and DarkFlats along with Lights

Since version 1083 I always get an error with the FLATs. At 1082 everything ran smoothly (same files).

CRITICAL WARNING: flat-field calibration can not be performed correctly!

To be able to perform accurate flat-field calibration,
the provided flats need to be calibrated by either

- a MasterBias, of the same ISO/gain value as the flat frame, or
- a MasterDarkFlat of the same ISO/gain value and the same exposure time as the flat frame, or
- both

Posted by: @romansellier

Hello,

I always get the attached warning message when loading Lights along with Flats and DarkFlats. I am using ASIAIR and the DarkFlats have the same exposure and gain as the Flats. The DarkFlats in ASIAIR were labelled as Darks (there is no separate DarkFlats categorisation there). As I am dithering and due to the good quality of my ASI 2600 MC Pro, I did not make any separate Darks or Bias frames.

When continuing ignoring the APP warning, the integrated image finally shows some severe overvignetting.

As an alternative, I loaded the DarkFlats in the Bias section. Then no warning message shows up any longer, but I am not really sure, if the Flats are then corrected by the DarkFlats accordingly.

Could you please let me know how I would have to load the DarkFlats?

 

Thanks a lot,

Roman

 

Dear Roman,

To be able to apply flats correctly, you also need to calibrate your lights with either bias or darks. If you don't flat-field correction can never work because the sensor pedestal is not removed from the lights.

So the issue is not your flats or your flatdarks. The issue is that you have an incomplete workflow with your lights. You really need to calibrate them.

If you load your flatdarks as bias as well, then yes, it works because then the lights are subtracted with those flatdarks and then the sensor pedestal is removed from the lights as required. But of course it is much better to use bias or darks depending on the sensor characteristics that you are dealing with.

Mabula

Posted by: @enno29

Since version 1083 I always get an error with the FLATs. At 1082 everything ran smoothly (same files).

 

CRITICAL WARNING: flat-field calibration can not be performed correctly!

To be able to perform accurate flat-field calibration,
the provided flats need to be calibrated by either

- a MasterBias, of the same ISO/gain value as the flat frame, or
- a MasterDarkFlat of the same ISO/gain value and the same exposure time as the flat frame, or
- both

 

 

Dear Enrico,

You are not receiving an error, but an important warning.

What are you loading? Lights, flats, darks, bias, flatdarks ? Are you making sure that both the lights and the flats are correctly calibrated?

Mabula

@mabula-admin lights, flats and darks. So if I do the same in version 1082, everything goes through without warning.

@mabula-admin lights, flats and darks. So if I do the same in version 1082, everything goes through without warning.

@mabula-admin

Hi Mabula,

thanks a lot for the quick response.

To confirm that I understood you correctly, I can either

- load the DarkFlats both in the DarkFlats and Bias section at the same time (interim but not perfect solution)

- make separate Bias frames in the future (preferred solution)

Is this correct?

Thanks again and regards

Roman

Posted by: @enno29

@mabula-admin lights, flats and darks. So if I do the same in version 1082, everything goes through without warning.

That should not happen, because then the flats are not calibrated with either bias or flatdarks. So you need to add either bias or darkflats.

Are you absolutely sure that 1.082 has no problem there? I ask because in that regard nothing changed between 1.082 and 1.083.

Mabula

Posted by: @romansellier

@mabula-admin

Hi Mabula,

thanks a lot for the quick response.

To confirm that I understood you correctly, I can either

- load the DarkFlats both in the DarkFlats and Bias section at the same time (interim but not perfect solution)

- make separate Bias frames in the future (preferred solution)

Is this correct?

Thanks again and regards

Roman

That is 100% correct Roman 😉

Mabula

@mabula-admin

Perfect, thanks Mabula! 🙂

@mabula-admin I must apologize. I forgot to load the MasterBIAS. Now it's working. This is what happens when you haven't worked with APP for a few months 😉

Posted by: @enno29

@mabula-admin I must apologize. I forgot to load the MasterBIAS. Now it's working. This is what happens when you haven't worked with APP for a few months 😉

Okay Enrico, no problem, glad it is solved and all okay now 😉

Mabula