STScI Logo

Hubble Space Telescope
FOC Instrument Science Report 065

FOC Instrument Science Report 065  

"Reduction and Analysis of Objective Prism Images"  9/92
by W. Hack

Abstract excerpted from the report:

This paper discusses the calibration of the objective prisms and reduction 
techniques developed to analyze FOC objective prism spectra. The f/48 
objective prisms have not been calibrated in-flight due to lack of faint,
emission-line rich objects. The calibration of the f/96 objective prisms
reported in the FOC-Science Verification report (SV report) has been tested
using simulations. The simulations were reduced using several new IRAF tasks
and showed that the Far-UV prisms (FUVOP) are well calibrated while the Near-
UV prisms require further calibration. The application of the dispersion 
curves and the photometric response can produce calibrated FUVOP spectra and
calibrated NUVOP spectra with erros in flux of about 10% and 20-30%, 
respectively, at any given wavelength.

A new deconvolution technique has been developed which uses a user-supplied
catalog of PSFs. The effects of deconvolution using one PSF and using multiple
PSFs have been compared for their effectiveness in recovering or enhancing
spectral features and photometry. Because of the influence of the PSF across
the spectra, multiple PSFs should be used when deconvolving the spectra.