it doesn't hurt to take longer subexposures.

i like to get my signal's square root quite a bit bigger than the read noise
so that I am shot noise limited instead of read noise limited.

My camera is in the 9 electron range for read noise and m y gain is about
2.1 electrons per ADU

so long as i have 81 or more electrons, which is in the 200 or so ADU range
(after bias/dark subtraction) then I meet that criteria.

usually I just shoot 20 or 30 minutes and sometimes will go 45 minutes. I
stopped at 20 to prevent bad star blooming.


"Stefan Lilge" wrote in message
...
Richard, amazing depth for the rather short (at least by your standards)
exposure time. Maybe the long time for each exposure does the trick...

Stefan

"Richard Crisp" schrieb im Newsbeitrag
t...
this is the final of the three images from my fremont peak outing last
night. this is 4 x 20 minutes with Baader Halpha filter, FLI IMG6303E
camera and Pentax 150mm f/2.8 medium format (6x7) camera lens

http://www.narrowbandimaging.com/m24...03_bp_page.htm