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The efficiency curves for FOS-I and FOS-II are plotted as a function of wavelength in Figures gif and gif respectively. The peak efficiency of FOS-1 in first order is 76 per cent, and for FOS-2 is about 70 per cent.


Figure: The efficiency of FOS-1


Figure: The efficiency of FOS-2

The efficiency of the total system (atmosphere, telescope and FOS with the extended blue response CCD) derived from observations of flux standards under photometric conditions is 12.5% for FOS-1, and 17% for FOS-2, at 7000Å, measured at the zenith.

The AB magnitude for 1 photon/s/Å/ at the zenith is given in Tables gif and gif in Appendix gif.

Tue Aug 15 16:42:46 BST 1995