Subject: Re: Long Exposures

From: Ron Rechenmacher

Submitted: Mon, 19 Feb 1996 17:46:38 -0600

Message number: 21 (previous: 20, next: 22 up: Index)

Hi,

	I looked at the code (this is for when the vme board controls
the shutter via the cdiom) and there seems to be an arbitrary
upper limit to the exposure timing of 700 seconds, but I could easily
changed that to be up to 40 million seconds.

Ron


annis@sdss.fnal.gov (James Annis) writes:
> This is a reply to Kris Stanek:
> 
> The shutter is not set up to time images longer
> than 720 seconds. To do so, you will have to either time it 
> manually, or rely on the Unix "sleep" command to time for you.
> The latter can be inaccurate if the machine gets heavily loaded.
> How innaccurate is not known to me.
> 
> So, I made a routine that should work, but it is
> a low level command:
> 
> #############################################################################
> #                       Long Stares Operation                               #
> #############################################################################
>                         # exposures longer than 720 seconds
>                         # must be done with a less accurate timer,
>                         # namely the Unix sleep command.
>                         # a recipe for a 900 second exposure follows:
> fnstar-OAC> sxt 900                     # set exposure time to 900
> fnstar-OAC> cc beginSleepReadout        # take exposure
>                         # and to take a dark frame:
> fnstar-OAC> cc beginSleepReadout 0      # take dark, 900 sec exposure
> 
> #############################################################################
> 
> that is cut and pasted from the primer from a new version of
> DOP that I cut. Instead of "setup dop", do a "setup dop devel"
> and you will be able to use "beginSleepReadout". It will find
> its way into the real dop in a few weeks.
> 
> jim
> 
> 
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