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Hubble Space Telescope
GHRS Instrument Science Report 083

GHRS Instrument Science Report No. 83

"The Far Wings of the GHRS PSF"

A.B. Schultz, S. Hulbert, L. Sherbert, and D. Soderblom

September 21, 1997


The GHRS Point Spread Function (PSF) was measured directly by stepping
(dwell scan) the Small Science Aperture across the star HD106343
(program ID: 6210) using the G160M and G270M gratings. Two scan
directions were sampled, along the instrument x-axis at wavelengths
1400A and 2700A, and along the +y-axis at 2700A. The scan steps were
spaced 0.4 arcsecond apart and went out to a radius of 3.0 arcsec from
the star. RAPID mode (sample time of 1 second) was used to measure the
counts at each dwell position. Nine points (9) were extracted from the
data to define the PSF envelope. The PSF exhibits a low intensity side
lobe peaking at a radial distance of ~2.0 arcseconds.