Flux standard data and empirical throughput

The figure below shows the results from throughput measurements of flux standards using the EEV12 and RED+ CCDs in the blue and red arm respectively, and the new 5300 dichroic. The Y-axis is the apparent AB magnitude of star observed at zenith which gives one detected photon per second per Angstrom. The lowest resolution grating was used (R158R) in the red arm (without any order sorter filter) and the R300B grating was used in the blue arm. Spectra were obtained with a wide slit (10 arcsec). The conditions were photometric, with negligible dust levels present. This figure shows the response of the whole ISIS red and blue arms (i.e. WHT primary + secondary + dichroic + ISIS optics + detector response) from ~3200 to ~9300Å.