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 |
31-51% |
2 pixel spectral resolution when used with a MAMA detector |
|
52X0.1
|
yes |
50-75% |
2 pixel spectral resolution when used with the CCD |
|
52X0.2
|
no |
65-87% |
Good compromise between photometric throughput and spectral purity |
|
52X0.5
|
no |
83-93% |
Good spectrophotometry for point sources, but spectral purity is degraded
significantly |
|
52X2 |
no |
97-99% |
Best spectrophotometry for point sources, but wings of PSF compromise
spectral purity
|
|
52X0.2F1
|
no |
65-87% |
Nomenclature used to request placement of source behind a 0.5x0.2 arcsec
occulting bar
|
To mitigate CTE 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 |
35-59% |
2 pixel spectral resolution for E140M and E230M gratings |
|
0.2X0.09
|
yes |
42-69% |
2 pixel spectral resolution for E140H and E230H gratings |
|
0.2X0.2
|
no |
54-78% |
Good compromise between photometric throughput and spectral purity.
Photometric reference aperture. |
|
6X0.2
|
no |
66-84% |
Use to map extended sources with isolated emission lines. Severe order
overlap.
|
|
0.1X0.03
|
2
stage
|
20-37% |
Smallest STIS aperture. Best spectral resolution. |
|
0.2X0.06FP
|
yes |
38-64% |
Can reduce the impact of fixed pattern noise |
|
0.2X0.2FP
|
no |
55-78% |
Can reduce the impact of fixed pattern noise |
|
0.2X0.05ND
|
yes |
0.18-0.67% |
Use to observe sources too bright for standard apertures |
|
0.3X0.05ND
|
yes |
0.03-0.07% |
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.
Diagrams of the
52X0.2F1 occulting bar,
52X0.1
occulting bars,
angled
slits, and
Fixed-Pattern (FP) slits are available.
|
 |
|
