Flats... How Long/Many etc

[Mav359]

Hi guys i know how long, QTY BIAS & Dark Frames i need but i cant see it written down regarding flats.

How many do i need? how long do i expose for etc

Cheers

[RikM]

I normally take 31. DSS likes odd numbers. I set the camera to AV and let it decide its own optimal exposure time. I use a flat panel for illumination with a couple of sheets of paper to dim it a bit. My flat exposures on AV are normally about 1/100th sec.

[Mav359]

Cheers Rik

I have gone to the trouble of converting an old LCD monitor into a flat field panel and went to use last night for the first time and realized i didn't know how

[ollypenrice]

You want to expose till the peak of the histogram is between 1/3 to 2/3 of the way to saturation. Odd numbers are good in median combine. Diminishing returns set in at around 50 so 31 is good but 51 is even better. Unlikely that you'd find a difference.

Just use a master bias as a 'dark for flats' if you want to make a master flat.

Olly

[jgs001]

Av mode on an SLR gives you just about spot on exposures for the flats, as long as you don't have any exposure compensation set. I tend to shoot one in Av mode, then set back to manual and set that shutter speed. I normally shot 21 ish...