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Cycle 23 STIS Instrument Handbook
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Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 23 > Chapter 12: Special Uses of STIS > 12.6 Improving the Sampling of the Line Spread Function

12.6
In most configurations the point source spectral line FWHM is slightly less than two detector pixels (see Section 13.6). Most observations should not be affected, but if you are observing lines which are near to being unresolved in the grating of interest and require accurate line profiles, you can consider the following technique:
For MAMA observations, highres pixels may provide twice the sampling; however, flat-field variability may make it difficult to realize the benefit in resolution (see “Highres”). Note that all STIS data are taken by default in highres format, and then binned in calibration on the ground so all you need to do is recalibrate your data, changing the switch settings (see “STIS Calibration” chapter in the STIS Data Handbook) to fully exploit the highres data.
For MAMA echelle observations, consider using the very small 0.1x0.03 aperture. When used with very high signal-to-noise data in the highres format and with specialized data reduction techniques, resolutions as high as 200,000 are possible with the E140H and E230H echelle gratings (Jenkins & Tripp 2001, ApJS, 137, 297).

Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 23 > Chapter 12: Special Uses of STIS > 12.6 Improving the Sampling of the Line Spread Function

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