Hamilton Throughput (with 3-meter and CAT)
The plots shown below give the full-system throughput (telescope plus
spectrograph plus detector) as a percentage of the light incident on the
primary mirrors of the 3-m and CAT telescopes.
The plots are derived from standard star observations made
using old dewar 8, a CCD that is no longer in use. The plots, which show
overall performance with one of the two CCD's (dewar 6) currently available
with the Hamilton, were extrapolated from the original measurements by
comparing the QE's of old dewar 8 and dewar 6.
Not given here are preformance curves for the second array currently
available with the Hamilton: the LBL high-resistivity device now in dewar 8.
Overall performance with the LBL device may be roughly estimated by comparing
the CCD's relative QE's. See the
Dewars and Detectors
section of this manual. (When choosing the detector for your
program, bear in mind that the two devices differ in several other
characteristics besides QE.).
Hamilton performance, particualarly with the 3-meter,
is strongly seeing-dependent. The throughput measurements were made with
a 4-arcsecond slit in 1 to 2 arcsecond seeing; the typical 3-meter
observing slit is just over 1-arcsecond.
Note the change in the Y-axis scale of the CAT plot compared to the
3-meter plot.
The better relative performance of the CAT results from
the larger projected slit afforded by that telescope's more favorable plate
scale. (On a typical night, the CAT's performance is only about a factor
of seventeen less than the 3-meter's, rather than the factor of twenty-five
predicted by relative apertures alone.)