Shooting lights and darks.

[MarkMayf]

Quick question.

When shooting darks am I right in thinking I use the same camera settings as used for the image?

And with lights I don't use the same settings bit something like half the exposure time?

Thank you.

[ollypenrice]

1) Yes and 2) No.

Darks must mirror exactly the settings and temperature used for the images.

By 'lights' I suspect you mean flats? Images of a smooth white surface used to calibrate out uneven illumination due to vignetting and dust bunnies. (The term 'lights' is used for the images themselves, not the flats.)

Flats should be exposed to give a histogram peak about a third of the way up the range, so the peak will be a third of the way to the right in most displays. In theory you can go as high as 2/3 but I'd advise a third. Flats themselves need to be dark frame corrected but there is no need whatever to shoot dedicated 'darks for flats.' Just use a master bias (an averaged set of 30 bias frames) as darks for your flats. This works perfectly.

Olly

http://ollypenrice.s...39556&k=FGgG233

[VigdisVZ]

Darks, just use the same settings but put the telescope cap on (or remove the camera and shoot with a cover). As long as the camera is the same temperature ie dont bring it in. Basicly you want to replicate the noise camera adds so you can subtract it from the image.

Lights "is" the image, the data, what you base everything around. Maybe youre thinking about flats?

Flats can be really short just a long as the opctical train is not altered in any way and you get that around 1/3 - 2/3 saturation Olly mentions. The idea is to replicate the faults in the optical train with a grey "flat" image so you can subtract those errors from the final image.

[MarkMayf]

Flats, yes sorry!

Thank You!