Flat Frames - a question about colour

[Steve 1962]

Sorry if I'm asking a daft question here.

I have a modified EOS1000d and I use it with a CLS Clip filter which is distinctly blue - but with the red tint to the modified camera, the colour balance in images doesn't look too bad.

My problem is that when I take a set of Flats - they come out blue (because of the filter) - so when they're incorporated with Darks and Bias Frames into an image - the image appears orange(ish).

Since (I believe) Flats are all about dust and vignetting in the optical train, and not about colour, my question is - should Flats be taken as B&W images or desaturated before use ..or, as usual, am I missing something here??

Thanks for any help / advice that anyone can give.

Cheers

Steve

[jgs001]

Steve, I have the CLS filter and get the same blue tint... I've never worried about it though... It's my understanding, that DSS always applies the flats as a greyscale image, so the colour cast is irrelevant.

[Steve 1962]

Thanks John

I'm using Nebulosity 2 - and it seems to have a dramatic effect on the colour - I'll try a "desaturated" flat and see if that makes a difference

Thanks again

Steve

[Glider]

Are you taking RAW files? Take RAWS. Process them in DSS; let DSS handle the preprocessing(calibration), stacking, deBayer, process resultant file in Photoshop.

[Steve 1962]

Thanks for the advice Glider!

[martin_h]

In Nebulosity 2 shoot the flats in raw format, then in Edit-Prefrences, scroll down to the Processing section and select Flat Processing 2x2 mean, or 3x3 mean. This destroyes the bayer matrix in the flat and renders it grey scale

[Steve 1962]

That works ... as does DSS ... thanks to both of you

Steve

[dph1nm]

Since (I believe) Flats are all about dust and vignetting in the optical train, and not about colour

Actually, they also measure variations in the response of individual pixels to light, which may well be colour dependent. So strictly speaking you should take flats with the same colour as your image frames, but I wouldn't worry about it unless you are trying to do photometry at the milli-magnitude level.

NigelM