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During the 2002-01-03 night, it was determined the spatial focus using different ISIS dicroics. The spectral focus was fix in the afternoon for the RED and BLUE arms of ISIS without any dichroic. During the night, we corrected the spectral focus offset introduced in the RED arm for every dichroic placed in the beam. The general set-up of the instrument was:
ISIS Arm Grating Central wavelength Collimator Position --------------------------------------------- RED R316R 7500 8784 BLUE R600B 4500 6279
The results obtained observing a bright star close to the zenit and using a slit width of 1 arcsec are summarized in the following table.
ISIS arm | BFOLD position | Best telescope focus _______________________________________________ RED Clear 97.75 BLUE Mirror 97.75 RED 6100 97.70 BLUE 6100 97.75 RED 5700 97.70 BLUE 5700 97.70 RED 4500 97.75 BLUE 4500 97.75 _______________________________________________
