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Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 14

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F25QTZ-FUV-MAMA, Longpass

Description

The F25QTZ filter with the FUV-MAMA provides high-throughput broad-band far-UV imaging with better rejection of geocoronal emission than the F25MAMA or F25SRF2 modes and the same field of view and spatial resolution.

Recommended Uses

Recommended filter for broad-band far-UV imaging of faint targets.

Special Considerations

With this filter the background is dominated by detector dark current. The dark current is not constant across the detector and not constant in time. This could limit the sensitivity for very extended faint targets, however, note that the FUV-MAMA dark is extremely low.

Users may also want to consider whether the ACS SBC detector might be better for their observing program.

Pivot (Å)
FWHM (Å)
AB mag zeropoint
Speak
B
R80 (arcsec) Flux in central pixel
1595.1
227.8
21.539
4.29e+13
225.0
0.28
10%

Figure 14.78: F25QTZ FUV-MAMA Integrated System Throughput and Redleak


 

Table 14.32: Throughput and Sensitivity for F25QTZ FUV-MAMA
l
Sensitivity
Throughput %
1475.
3.93E13
1.17
1500.
4.25E13
1.24
1525.
4.05E13
1.17
1550.
3.75E13
1.06
1575.
3.38E13
0.94
1600.
3.01E13
0.83
1625.
2.72E13
0.73
1650.
2.46E13
0.65
1675.
2.19E13
0.57
1700.
1.85E13
0.48
1725.
1.60E13
0.41
1750.
1.38E13
0.35
1775.
1.16E13
0.29
1800.
9.75E12
0.24
1825.
7.59E12
0.18
1850.
3.75E12
0.09
1875.
1.83E12
0.04
1900.
8.71E11
0.02

Figure 14.79: Point source S/N vs. V+AB for the F25QTZ FUV-MAMA mode. Curves are labeled by required exposure time (sec).


 
Figure 14.80: Extended source S/N vs. V+AB for the F25QTZ FUV-MAMA mode. Top curves are for an area of 0.2 arcsec2; bottom curves are for 1 arcsec2. Average sky assumed. Curves are labeled by required exposure time (sec).


 

Table 14.33: Radial Profile for F25QTZ*
Radius
 
Fraction of Energy Encircled
Pix
arcsec
intensity
1
0.024
3.961e-02
0.172
2
0.037
2.515e-02
0.287
2
0.049
1.505e-02
0.398
3
0.073
5.412e-03
0.532
4
0.098
2.570e-03
0.609
5
0.122
1.373e-03
0.659
10
0.245
2.735e-04
0.778
15
0.367
1.447e-04
0.851
20
0.490
7.887e-05
0.909
25
0.613
4.703e-05
0.953
30
0.735
2.117e-05
0.980
40
0.980
1.135e-05
1.000

* See STIS ISR 2003-01.

Figure 14.81: Point Source Encircled Energy for F25QTZ FUV-MAMA


 
Figure 14.82: Point Source Intensity vs. Radius for F25QTZ FUV-MAMA


 
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