INSTRUMENT SCIENCE REPORT
	TELESCOPE	FOS/CAL-018
	SGIENCE
	INSTFFUTE
FOS Line Widths (FWHM) as a Function of Aperture Size


ALJTHOR: Anne L. Kinney and Holland C. Ford	DATE:  May 1985 


FOS Line Widths (FWHM) as a Function of Aperture Size

A.L. Kinney and H.C. Ford

May 1985

Introduction and Summar~:

When observing extended sources stich as galaxies and nebulae which
fiu the FOS entrance aperture, the Iine profile will be a function of
the aperture size. We have characterized the line widths for the ten
entrance apertures on the red and the blue sides by Ineasuring the
FWHM of emission lines in spectra of an external calibration source
taken during the last FOS therinal-vacuum calibration at Martin
Marietta.


The FWHMs are approximately equal to the aperture size used in the
observation. The widths do not appear to vary when different gratings
are used, and the asymmetry for lines 011 the edge of the diode array
as shown by a ray trace, appear negligible. For the smallest aperture,
80% of the light in the line falls within a width of one diode.