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Ant

Whats a DARK FLAT FILE?

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Just putting some files into DSS and I keep meaning to ask...

I know what a FLAT file is.

I know what a BIAS file is.

I know what a DARK file is.

But what's a DARK FLAT file?

Thanks

Ant

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It's an exposure the same length as the flat frame but with the lens/scope covered up. It helps to reduce the noise in the flat frames.

Regards

Kevin

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Ahhh that makes sense :icon_salut:

Thanks Kevin

Ant

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Every time I open DSS I ask myself this same question, I'm glad someone else thought to actually voice it!

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It's an exposure the same length as the flat frame but with the lens/scope covered up. It helps to reduce the noise in the flat frames.

Regards

Kevin

So what is the difference between that and a dark then?

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The flat frame is of an even field, with the camera decided the exposure length (AV mode).

So the Dark will match the Light in duration, but the Dark Flat will match the Flat in duration.

If I've got that right.

Ant

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That's right Ant. One word of caution... If you are using Bias frames you don't need dark flats, and vice versa. If you use both then weird things start to happen (I think it's down to the removal of the bias current twice but I've no clue about that level of stuff)

I used to take a sequence of dark flats as well as the Bias frames, but you can save some time not taking the dark flats and use the stored Bias frames instead. Thanks to whoever, I think it was Martin, that pointed out the Bias frames.

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Ah so it is just a dark but timed for the flat. OK.

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pedantic, picky old git that I am all the reference works refer to them as flat darks.

Dennis

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interesting, since light images experience fixed pattern noise, which is removed with flats, and since dark frames have dark fixed pattern noise, could one flatten a dark to remove dark fixed pattern noise.

Its worth an experiment......

paul

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