Subject: Message from Russet: New DIS gratings

From: Michael Strauss

Submitted: Mon, 17 Jul 2006 09:25:36 -0400

Message number: 978 (previous: 977, next: 979 up: Index)

Hello all,

Last month we received two new gratings for DIS -- the B400 and R300
gratings described in Jon Holtzman's message at .  We
have mounted and characterized these gratings, and they both look
very nice.  The blue one gives a modest improvement in throughput and
a slightly higher resolution than the old blue low grating, and the
red one has distinctly better throughput along with a bluer blaze
(good for Halpha) compared to the old red medium grating.  Each
grating provides full spectral coverage from the dichroic cutoff to
the blue or red limit of the spectrograph.

The B400 and R300 gratings will now become the standard
lower-resolution setup for DIS.  If observers request low resolution
or blue low/red medium in their proposals or setup emails, we will
assume they want the new gratings UNLESS there is an explicit request
for the older ones (for example, to match earlier data).  So please
be specific in your requests.

Note that the old blue medium (B600) grating has been removed from
its mount for some measurements.  We are considering whether to
retire this grating and would like to hear from any observers
interested in working with it in the future.  The grating does have a
very blue blaze wavelength and therefore might be useful to observers
interested in features near the blue cutoff of the spectrograph;
however, the grating has suffered some damage in recent years and is
considered somewhat expendable.  If anyone wishes to use this
grating, let us know as soon as possible.

The high resolution gratings described in Jon's message have not been
delivered yet.  Like the new lower-res gratings, they will be tested
and characterized thoroughly before they become the default.

				    Russet McMillan.

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