Re: CCD sensitivity and resolution

On Sat, 26 Jan 2008 16:45:30 GMT, Davoud <star@xxxxxxx> wrote:

About three minutes.

The magnitudes (21--or less) are correct, but I made a misstatement. I
see that GSC 2.2 has a magnitude limit of 19.5. Sure enough, using
XEPhem with field stars set to mag 30, the dimmest stars displayed are
in the mag 19 range.

Yes, mag 19 sounds reasonable for three minute exposures. I've got
images showing stars around mag 21, but with exposure times more in the
hour range (and with less sky background).

I have stacks of FITS images that show stars
dimmer than shown in XEPhem, though they don't always show up in my
reduced images because I try to process for aesthetics.

Makes sense. The dimmest stars are going to be right up against the
noise floor, and when you process for aesthetics, you usually pull up
your black level to hide that noise. It's a fun exercise to see just how
deep you can get- something you can try if you ever get a long enough
stretch of good conditions that you can "waste" some time on
non-aesthetic imaging <g>. From your comments over the last couple of
years (since you got some top-notch equipment on line, naturally) it
sounds like your good imaging opportunities have been depressingly rare.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
.

Relevant Pages