FOS Instrument Science Report 096

"Location of FOS Spectra: Cycle 1 and Cycle 2 Results"
by Anuradha Koratkar and Cynthia J. Taylor

Abstract excerpted from the report:
	The optimal locations of the FOS spectra were determined for non-
	polarized grating/detector combinations using calibration maps obtained
	during Cycle 1 and Cycle 2 (proposal IDs 2817 and 4097).  The location
	of the spectrum as a function of diode number deviates from linearity	
	by up to +/- 20 YBASE units because of small distortions of the magnetic
	fields in the Digicons.  In addition, the spectra are rotated by small
	angles (typically 0.05 degree for the high resolution gratings) with
	respect to the diode array.  New optimal locations of the spectra
	(YBASES) determined during the analysis have been updated in the
	Project Data Base (PDB) on August 11 1993.

	The anaylsis showed that there is a trend in the position of the spectra
	for all gratings observed with the blue detector, while the locations of
	the spectra for all gratings with the red detector are relatively 
	stable.  Photometric errors and errors in the measured shape of the
	continuum due to the incorrect usage of YBASE values for Cycle 2 and 
	early Cycle 3 observations are typically <3% on the blueside and <1% on
	the redside.

For more information, please contact the above authors.