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Subject: RE: [M]: [M] Shooting Jupiter with a CCD Camera
From: Michael Hart
Reply To: mapug@shore.net
Date: Sun Oct 19 00:59:57 1997

On Saturday, October 18, 1997 9:12 AM, Jill G. Viser wrote:
> Dear Mr. Hart:
>
> I was examining exposures taken of Jupiter the same night
> on the same scope. The exposures ranged from .5 sec to
> .01 sec. Both the .05 and the .01 sec exposures are slightly
> dimmer than the .1 sec excposure although they are indistinguishable
> from each other.
>
> Page 25 of the operating manual states that the exposure time limit
> with the shutter is .11 sec.
>
> The images would appear to be from shorter that .11 sec. exposures.
> Perhaps the shutter is capable of sometimes running faster that
> .11 seconds and when it doesn't that is what is giving the random
> shutter errors?
>
> I'll email SBIG and ask them.
>
> Gene Horr

I checked my CCDOPS for Windows ver 1.09. You are correct that the
software does accept 0.01 second exposures. It also records the 0.01
second value in the header. But that is not the actual exposure time.
I believe you are also correct that the shutter is capable of exposures
shorter than 0.11 seconds. I suspect CCDSoft resets to lowest value
that can be reproduced reliably. I timed several shots and it appears the
difference between a 0.11 second exposure and 0.01 second exposure
is very slight. Sometimes the 0.01 second shot is longer than the 0.11
second shot. As I suspected, timing become less repeatable on
shorter exposures as follows:

0.2=2.3% 0.11=3.6% 0.01= 12.2%.,


Please post what you learn.



--
Michael Hart
Husen Observatory
mhart@netexpress.net