Date: Fri, 25 May 2001 00:01:55 -0500 (CDT)
From: Stephen Kent
Subject: Re: 2.5m obslog 20010523 (MJD 52053)
Regarding the instructions in the observing plan for stripe 82 S,
Atsuko asked for feedback:
>
> Run 2336 Stripe 82 S Lambda=122 ->  131 or so is intended for science
> Steve said in the science plan that "Note: extend this scan to am
> twilight". We only had 20 min or so left before twilight started, we
> decided to do this stripe as our last stripe of the night.
>
> This run has worse seeing than the other scans. The seeing was
> variable. We got the first skyL, skyR errors in the watcher
> at skyL 04:49:51. We hope the pipeline can reduce all or most
> of the data.  Please tell us how much twilight we can tolerate
> so that we know how much to push for th eother "extend this scan
> to am twilight" stripes.
The instructions in the science plan were not intended to imply that the
twilight constraints should be different than for any other run. Rather,
the spirit of the instructions were intended to be that because the 82 S
segment is so short (we are observing the very beginning of the stripe),
once it is observed, you might as well just keep scanning away on this
stripe rather than start some other stripe since we want repeat
observations of stripe 82 anyway.
For the record (and I have posted this information before), the most that
one can push twilight is about 5 minutes beyond -18 degree twilight, at
which point the u' band sky intensity starts going bonkers.  The -18
degree twilight times are listed in the plate inventory database under
"plan a night's observing".
Steve