We are in the process of determining the throughput of DEIMOS in spectroscopic mode
             for all the gratings and grating tilts of relevance. What you will find in the links below are down-
             loadable plots and tables with the results of observations of the star BD+28 4211, taken under
             photometric conditions during the months of June through September/2002.

                       Our throughputs are defined as follows:

             Throughput =  Nd/Nt

                        where:

             Nd = Number of photons detected
             Nt = Number of photons hitting the telescope's primary mirror

                        The latter is given by:

             Nt = Nst * 10 ** (-0.4*airmass*ext(lambda))

                         where Nst is the star's photon flux, in photon/sq.cm/s, taken from the HST/CALSPEC
             database of standard star fluxes, and ext(lambda) is the mean monochromatic extinction coefficient
             for Mauna Kea.
 
 

                       Throughput data taken with various combinations of grating tilts and order-blocking filters
              for the aluminum 600 and 900 l/mm gratings, and a more limited, preliminary set of data for the
              gold 830 and 1200 l/mm gratings are available. A more comprehensive data set for the latter
              two gratings and for the aluminum 1200 l/mm grating are in the process of being collected and
              reduced, and will be made available soon. By following the links below, you'll be able to view plots,
              or download postscript files and ascII tables with the measured throughputs.

                       We note that these throughputs are higher by a factor of 1.056 than the values from an earlier
              release, due to a correction in the value adopted for the collective area of the Keck telescope.
 

            Aluminum 600 l/mm

            Aluminum 900 l/mm

            Gold 1200 l/mm

            Gold 830 l/mm:      download ps      view plot