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.