Apertures

Accordion

• 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 in Appendix A.2 of the instrument handbook.