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CRSP Changes for Fall 1992 (1Sep92)
(from KPNO, NOAO Newsletter No. 31, 1 September 1992)

Two events scheduled for this summer should result in changes to the
Infrared Cryogenic Spectrometer operation. The first is the
installation of an f/15 secondary at the 4-m, giving f/15 operation at
all three telescopes on which CRSP operates. This should yield
approximately the same pixel scale (0.9 arcsec) as before, while
illuminating most of the array in the cross-dispersion dimension.

The second event comes about due to the IRIM upgrades discussed
elsewhere in this Newsletter. Since IRIM is getting a larger format
detector (see previous article), the ex-IRIM array is available for
installation in CRSP. This detector has a number of potential
advantages, including highly desirable cosmetic quality, no QE gradient
along the columns, and a somewhat more linear behavior. The residual
image effect seen with the present CRSP array is much smaller (or
perhaps absent) in the IRIM array, so it may be possible to operate
without the nuisance of the vgate cycle before each picture.

Finally, for those who may wish to correct previously obtained CRSP
data for detector non-linearity, a recent lab test (possibly the last
with the old detector) showed that data <  13000 ADU could be linearized
by the third-order function

ADU' = ADU [ 0.999 + 7.06 E-06 * ADU + 2.19 E-10 * ADU**2 ]

For those using the IRAF ctio.irlincor task, the three coefficients are
0.999, 0.231, and 0.235.

Dick Joyce

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