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DBSP Throughput CurvesAbstract![]() Red channel DBSP throughput curve for the 600/1000 grating/D55 dichroic filter combination at a grating angle of 29.5°. (Palomar/Caltech) This page reports on estimated Hale Telescope Double Spectrograph (DBSP) throughput in various configurations based on spectrophotometric standard data taken in 2010. These data were acquired prior to the red side CCD upgrade (late 2011) and will be updated to current values in the near future. The blue side is not expected to change appreciably. Estimated throughput curves are shown for both the red and blue DBSP channels and for a representative set of spectrograph configurations. Throughput dependence on gratings, grating angles, and the dichroic filter are illustrated in these results. Observation, reduction, and throughput estimation procedures are described below. Evan Kirby calculated the throughput curves and wrote this page. Thanks to Jeff Hickey and Kevin Rykoski for obtaining the measurements. Special thanks to the DBSP observers in 2010 who sacrificed some dark time to make these measurements possible. Procedure
Throughput CurvesThe following table gives throughput curves in graphical (plot) and tabular (data) form for different combinations of gratings and dichroic filters. In each table cell, the letter B or R indicates that the curve is valid for the blue or red channel. The following number is the grating tilt in degrees. Click on plot to see the graph of the throughput curve. Click on data to see the ASCII table with wavelength and precentage throughput. The curves show the sky-to-detector, telescope+spectrograph, and spectrograph-only throughput measurements (see steps 8-10 above). Finally, the date of the throughput measurement is given in parentheses. Some spectrograph configurations have more than one throughput measurement. Differences between them can give a rough idea of the uncertainty of the measurements. Large fluctuations in throughput within a small spectral range are not real. These can be caused by incompletely excised telluric absorption bands or bad traces near the ends of the CCD.
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