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COB Moves to the Blanco 4-m Telescope (1Mar96)
(from CTIO, NOAO Newsletter No. 45, March 1996)

The NOAO Cryogenic Optical Bench (COB) will be moving from KPNO to CTIO
in October 1996, following a detector upgrade to a 512 x 512 Aladdin
InSb array in July-September. We are offering it for use at the 4-m
beginning in November 1996. Image scale with the f/14 secondary will be
0.1" per pixel, producing a 50" field of view.

This scale has been chosen to exploit tip-tilt image stabilization at
the 4-m. However, tip-tilt capability will NOT yet be available next
semester. Hence COB's temporary ecological niche is for programs which
benefit from oversampling the seeing limited image (typically 0.4"-0.7"
FWHM at K) in a restricted field of view. Operationally, optimum use
will be for broad and narrow band imaging and polarimetry, including
use of focal plane occulting spots with bright sources. A wide
assortment of filters is provided. While COB has a tunable Fabry-Perot
filter for imaging in the two micron window, and low resolution
spectroscopic capability using grisms, performance in these
low-background modes at this plate scale is likely to be unimpressive
without tip-tilt image sharpening. Spectroscopic proposals will be
better served by the upgraded IRS spectrometer, the subject of a
separate note in this Newsletter. We also discourage use beyond 2.5 um
until we have characterized system performance with the Wildfire controller
and larger array under CTIO background conditions.

Briefly, COB's capabilities include broadband imaging at 1.0 um, J, H,
K, K' (2.0-2.3 um), L, and L'; narrowband imaging at 1-4 um, including
1-2% filters at 1.08, 1.25, 1.28, 1.64, 1.99, 2.12, 2.14, 2.16, 2.22
(4%), 2.36, 2.38, 3.08, 3.30, 3.35, 3.40, 3.60, 4.00, 4.05 um;
polarimetry in broadband filters and 2 m narrowband filters;
occultation of a central bright source for imaging and polarimetry,
with focal plane spots occulting 2"-6" diameter on the 4-m; imaging at
resolution ~500 in the 2 um window using a tunable Fabry-Perot and the
narrowband filters as order sorters; spectroscopy at resolution ~300 in
the J, H, and K bands with a grism and focal plane slit.

Further information and performance estimates for COB can be found in
the CTIO Web pages, or from one of us.

Richard Elston, Ron Probst

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