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