Target ADU for DSLR flats

I’m using a Canon T2i (550D) for imaging. In the flats wizard, what should the target mean ADU be?


The ‘very old’ rule of thumb is whatever time gets your histogram roughly 1/3 to 1/2. It’ll vary throughout the dawn/dusk as the sun rises/goes down.

I’d suggest doing your times manually using that method as I read through your thread on Astronomy Forum. Or, maybe it’s calculating it wrong?

In case someone wants to read it.