Rate my Flats

[Dann]

Hi folks

Whilst the weather is naff I thought I would try to learn what I can indoors so I don't face too many avoidable problems when I attempt my first real imaging session.

I used the laptop/notepad trick with a couple of pieces of paper over the front as others have suggested. Somewhere it was suggested I put my DSLR into 'AV' mode and let the camera chose it own settings. My Nikon doesn't seem to have an 'AV' mode but im told the 'A' (aperture priority) mode on the D40 is the same, the thing is it complained due to the lack of lens in every mode apart from 'M' manual. No doubt there is a solution to this?

Anyway I took a series of shots to try and roughly work out what camera settings I should use with this method of taking flats.

Firstly am I right in thinking that nothing in the optical system should change (focus, camera and scope orientation etc) but the ISO used for flats doesn't have to match that of the lights and darks?

Below are some examples of the flats I took along with their histograms, all at ISO800. Im assuming the brightest one is a no no but are any of these suitable as flats, am I headed in the right direction?

Thanks for your help as always

[roundycat]

It is a very simple and quick matter to take 3 flats and apply them to an image. If it gets rid of the dust, vignettes and fixed pattern noise it is a good flat. Take some more and make a master from ten or a dozen.

Dennis

[steppenwolf]

Firstly am I right in thinking that nothing in the optical system should change (focus, camera and scope orientation etc) but the ISO used for flats doesn't have to match that of the lights and darks?

That's correct on all counts and quite critical for removal of dust bunnies.

Your third image (bottom left) looks most promising.

[Psychobilly]

I keep the ISO the same as well...for all Lights,Darks,Flats and Bias...