Supported and Available Apertures
The tables below provide a complete list of supported STIS apertures for spectroscopy, together with comments regarding their characteristics or purposes. For most apertures, the numbers in the aperture name are the length in the spatial direction followed by the width in the dispersion direction in arcseconds.
Only a small fraction of the 65 available spectroscopic apertures are currently supported on STIS. For more information on the available but unsupported apertures, see Appendix A.2.
For more detailed information regarding specific apertures see the Instrument Handbook.
Accordion
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.
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 in Appendix A.2 of the instrument handbook.