Subject: Re: 2.5m obslog 20030204 (MJD 52675)
Date: Wed,  5 Feb 2003 19:19:00 -0700 (MST)
From: harvanek@apo.nmsu.edu (Mike Harvanek)
From the 52675 log:
> > Plate 1247 (cartridge 2): Guide stars on the gotoField.  The 1st
> > exposure was 20 minutes long and conditions were decent (80%
> > efficiency, 2" seeing, not much moon) but we got (S/N)^2  > for b1 and b2 and just barely above 2 for r1 and r2.  Most of
> > the exposure was obtained before twilight ended but we still
> > expected much higher signal.  Since there is no mention of a
> > (S/N)^2 requirement for the blue chips on Orion plates,
Pete writes:
> Did anyone look at the plot of the distribution of S/N against magnitude from
> the SoS pages?  (I can't from home - my Postscript view is broken).
>
> Several type of non-survey plate get strange S/N summary results from SoS
> because the magnitude range is not what it was designed to deal with.  In
> particular is the mags are all clumped at one end, it is not great at
> extrapolating the fit to S/N v. mag to give the S/N at the "standard"
> magnitudes reported on the web page.  Maybe that's what happened here?
Yes, we looked at the plots but this was not the issue and we knew that
before we looked at the plots.  There were actually two different and
separate issues that my log entry attempted to document.
1) Based on the observations of an Orion plate from the previous night
(1244 on 52674) and given the conditions in which the current plate
(1247) was being observed, we were expecting much higher (S/N)^2 in
all chips, not just the blue.  We were aware of the fact that the
objects were dimmer in blue.  We were wondering if there might be a
problem with this specific plate (e.g., drilling), not with just the
blue side or the Orion plates in general.
2) Normally, if (S/N)^2  15 in R ONLY.  Thus, we were
wondering if frames with (S/N)^2 > 2 for the red chips but (S/N)^2  Also - no data is present for b1.
Well, technically there is.  It just isn't good - (S/N)^2 of 1.0 and 1.7
for the 2 exposures.  Since there is no mention of a blue (S/N)^2
requirement, we didn't know if you cared about the blue data or not.
We were just hoping that you might be able to use the data we acquired.
Please let us know if it is usable.  Thanks.
Mike