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Old 04-11-2013, 04:24 PM
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gregbradley
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Quote:
Originally Posted by nebulosity. View Post
The lights and darks were taken at the same ISO(1600) and exposure, the flats and bias' were different, do you think I should keep the same ISO for everything?

The flats were taken pointing at the western sky and it looked pretty even but as I got a 10x15 degree FOV it would probably be a good idea to put something over the front to make sure.

Does it matter what colour the flats are? And should I go by the camera Histogram or what it says on the computer? The both seem to be different.

I got a pic of a single Light, Flat, Dark and the processed image in B&W, seems to be lots of dusty stuff, if you haven't already guessed its the Hyades cluster.

Cheers
Jo
I would keep the ISO the same. Others who do regular DSLR imaging may chime in here. But as a basic you want the flats/darks to be under the same conditions as the lights with regards to temperature and focus, not rotate the camera, leave any filters in place.

I have always put a white tshirt over my scopes for dusk flats so I don't take a photo of a cloud or star which obviously was not in the image. As far as which colour - I don't know there. You could try making the exposure black and white by desaturating it and see if it makes a difference. It might. A flat is correcting for unevenness of illumination not colour so something blue may throw it off. I'd experiment doing it both ways and see how it goes.

As far as which histogram I think I would work off the camera's one.
Just in case the computer is applying some adjusment in the conversion from RAW. Many latest cameras tend to apply hot pixel suppression and possibly some noise reduction smoothing.

Greg.
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