Flats

[Camknox (Cameron)]

Hi folks,

I've been doing astrophotos for a bit now but I've never bothered with shooting flats, I sometimes use darks but not always. I've got myself a light box; homemade using an EL panel and some foam etc.

I've tried some sample shots and I'm not sure what I should be aiming for here. So with that in mind;

1. How long and what settings should I be exposing at? For example if my lights are 180s @ 800ISO f/0 my flats should be?

2. Is this a constant? I use APT for my image acquisition and it suggests a flat should be using the same ISO and I guess it determines the exposure time as it wont let me enter it.

[Atmos (Colin)]

Flats should be taken at the same ISO and optical configuration but the exposure time should just be as long as it takes to bring your histogram to 50-75% of saturation.

[rustigsmed (Russell)]

Hi cam,

Point to a blank part of the sky after sunset, turn the canon setting from manual to Av, and start snapping away. It will choose the exposure time automatically. Easy as!

Rusty