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Hubble Space Telescope
STIS Apertures


Supported Long Slits for First Order Gratings

Detectors record 25, 28, or 52 arcsec of spatial information. Various slit widths trade spectral purity against photometric throughput.

Aperture Peakup Throughput Comment
52X0.05 yes 21-51% 2 pixel spectral resolution when used with a MAMA detector
52X0.1 yes 33-75% 2 pixel spectral resolution when used with the CCD
52X0.2 no 40-87% Good compromise between photometric throughput and spectral purity
52X0.5 no 49-93% Good spectrophotometry for point sources, but spectral purity is degraded significantly
52X2 no 57-99% Best spectrophotometry for point sources, but wings of PSF compromise spectral purity
52X0.2F1 no 42-87% Nomenclature used to request placement of source behind a 0.5x0.2 arcsec occulting bar

To mitigate CTI degradation effects, pseudo-apertures have been defined with "E1" suffixes.

Supported Apertures for Echelle Gratings

Generally short enough to prevent order overlap. Various aperture widths trade resolution against photometric throughput.

Aperture Peakup Throughput Comment
0.2X0.06 yes 23-59% 2 pixel spectral resolution for E140M and E230M gratings
0.2X0.09 yes 27-69% 2 pixel spectral resolution for E140H and E230H gratings
0.2X0.2 no 34-83% Good compromise between photometric throughput and spectral purity. Photometric reference aperture.
6X0.2 no 50-85% Use to map extended sources with isolated emission lines. Severe order overlap.
0.1X0.03 2 stage 13-36% Smallest STIS aperture. Best spectral resolution.
0.2X0.06FP yes 25-64% Can reduce the impact of fixed pattern noise
0.2X0.2FP no 34-83% Can reduce the impact of fixed pattern noise
0.2X0.05ND yes 0.13-0.63% Use to observe sources too bright for standard apertures
0.3X0.05ND yes 0.02-0.07% Use to observe sources too bright for standard apertures

All supported combinations of aperture, optical element, and observing mode appear in Table 10.4 of the Phase 2 Proposal Instructions.

Only data obtained with supported apertures will be fully calibrated in the archive. Use of other available apertures must be justified.

A description of barred spectroscopy and diagrams of the 52X0.1 occulting bar, angled slits, and Fixed-Pattern (FP) slits are available.