Black flat frames

[Kevdan]

Hi all,

Took a load of pics last night of Bodes Nebula, but when it comes to taking flat frames They dont come out right, Following Steve Richards book Making Every Photon Count, I use VLB to produce the light, but how long should the exposure be for? because When I take them at the fastest shutter speed they just come out black but (and I cant find it now) Im sure I've read that the camera (in my case a pentax DSLR) should be set at fastest shutter speed.

Kev.

[Freddie]

Hi, flats should be set to give you about half to two thirds full saturation, you need to adjust exposure time to achieve this. It is Bias that are taken at shortest possible exposure time. Hope that helps.

[Kevdan]

flats should be set to give you about half to two thirds full saturation

Hi,

Ok so how do you measure saturation levels?

Kev.

[Spikey]

Look at the histogram that's produced by the exposure Kev.

[Tinker1947]

DSS has a help file and in there its give the information on what and how to do the various types of frames....

[steppenwolf]

If you set your DSLR camera to 'AV' mode and let the camera decide on the exposure length, you should end up with nicely exposed flat frames

[jgs001]

Kev, what Steve says, just make sure that you have no exposure compensation set on the camera before shooting.