Subject: April 14 UC phonecon comments

From: Alan Uomoto

Submitted: Wed, 16 Apr 1997 13:58:08 -0400

Message number: 140 (previous: 139, next: 141 up: Index)

COMMENTS ON THE USER COMMITTEE MINUTES

Medium Resolution Gratings

With luck, these could be installed by 4Q97.  They will probably replace
permanently the current low dispersion set since there is no easy way to
switch out gratings at night.  Programs in progress requiring the current
low dispersion gratings should be identified to make sure they can tolerate
the new gratings.

DIS Noise & the Two-Peaked Histogram

The two-peaked histogram in the red chip is still present, and whatever
causes it is probably causing the high read noise of 21 electrons (reported
by Karen Gloria).  The best this chip can deliver must be around 15
electrons, however, so unless this difference is preventing science, I'd
suggest spending time looking for new detectors instead of trying to
squeeze more performance out of these.

DIS UV Throughput Fix

I'd like to delay this operation into the 3Q98 because I can't guarantee a
reasonable schedule this year.  The incentive to fix in parallel an
"overall throughput decline" is lower since I suspect the reason for this
was the telescope, not the spectrograph (but if anyone has other thoughts,
I'd like to know).

Alan Uomoto
April 16, 1997

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