Date: Thu, 06 Feb 2003 15:32:35 -0700
From: "Peregrine M. McGehee"
Subject: Re: 2.5m obslog 20030204 (MJD 52675)
Observers,
I've had a look at the Spec1D outputs for plate 1247 and
recommend that it be reobserved.
Larry Carey reports that:
> Plates 1244, 45, 46, & 47 were drilled with a twist drill bit instead of
> with the spade bits we have been using for all production plates to date
> (to drill the science and guide fiber holes).  Before sending these plates
> to the mountain we tested all of the holes that the CMM would reach for
> both position and diameter (aprox. 630 to 650 holes per plate). The
> position error for the holes was no more than 7 microns (rms) on any of
> these plates. Our tolerance for acceptance is 9 microns max. The hole
> diameter measurements showed less scatter than the spade bits so i'm now
> considering switching to twist bits for production.
>
The target selection, design, regions on the sky, and the
fabrication process is identical for these plates 1244-1249.
Plate 1244 worked well yet plate 1247 had a (S/N)^2 ~1/3
of 1244.
As we are looking at switching over from spade to twist bits
in the plate drilling process it is important to understand
what happened.
Cartridge #1 presently has plate 1245 installed which will
serve as another test.
- Peregrine
--
Peregrine M. McGehee	peregrine@lanl.gov	(505) 667-3273
Sloan Digital Sky Survey / Spallation Neutron Source
MS H820, Los Alamos National Laboratory, Los Alamos, NM 87545