Question about flats

James Long wrote on Jun 06, 2009

Greetings all,

I am working with data from the ESO WFI, and I have a question about flats. What is the difference between a sky flat and a screen flat? Is a screen flat the same thing as a dome flat?

Thanks in advance :)

James

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Francisco Valdes wrote on Jun 06, 2009

Hello James,

Yes a screen flat is the same as a dome flat. A sky flat are exposures taken at twilight where any sources that shine through are hopefully removed when multiple exposures are stacked. A sky flat, also called a twilight flat, may do a better job of illumination correction but may also have more problems with gradients from the setting sun and sources.

Yours,
Frank Valdes

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Last post on Jun 06, 2009