Calibrate FLAT frames

Yes, you need either bias or darkflats to calibrate the flats. Why is it that you can't expose as long as a flat?

@vincent-mod 

I use a telescope subscription service, which doesn't offer the same dark exposure time as flat.
That's why I want to use a bias that doesn't matter the exposure time.

I understand that dark is the most suitable for removing noise related to exposure time, but I think that flat can use bias as a second best measure because of its short exposure time.
Is my understanding of this correct?

Thanks

Yes, flats can use the bias as well, they should have the same gain/offset settings though.

@mo-mo If you use darks and bias then APP can scale the darks to match the exposure times of the flats so the flats can be calibrated. The bias and darks then, as @vincent-mod also indicated, need to have the same gain, offset and temperature as the flats. 

@wvreeven 

Thank you Wouter
To calibrate flat, can I get better results that use bias and dark than using only bias?
As a premise, use the appropriate bias, dark.

@mo-mo In case of flats, there is not much difference between using bias only and using bias and darks. The reason is that flats contain so much signal that both bias and dark contribute very little to the raw subs.

@wvreeven

I will use the bias frame for calibration in the future.

Having less exposure time for the bias frame than for the dark frame is very important for shooting in a limited amount of time.

Thank you