Tim

[Coletc]

How do I take flats in Backyard EOS with a Canon 5D Mark III with Canon lenses

[astroman133]

Tim,

First, in the future, please provide a useful topic for your posts. For example, instead of "Tim" for the topci of your post you could choose something like "How to shoot flat frames?". This is helpful to others who want to read this thread and so to learn from your question and the answers..

There are several ways to shoot flats including sky flats, T-shirt flats, dome flats, lightbox flats, electrolumeniscent (EL) panel flats. What varies is the light source and the exposure. As far as BYE is concerned, you change the Frame type to Flat (this disables dithering), set the ISO to whatever you used shoot your lights, set the focus where it was for your lights (at infinity), put the lens in manual focus,  and select an exposure that gives you a well centered histogram and shoot the exposures.

I use an EL panel and exposures that are typically less than a second to get a well-centered histogram. I typically shoot the flats right after the lights and without touching the scope or camera. I also shoot 20 flat frames. Then I turn off the EL panel and shoot 20 dark flat frames. I could shoot bias frames or use a master bias from a library, as an alternative to the dark flats..