Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 17

25MAMA-NUV-MAMA, Clear

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Description

The 25MAMA mode with the NUV-MAMA provides high-throughput broad-band near-UV imaging with excellent pixel sampling and very high throughput at ~2500 Å. The field of view is 25x25 arcsec.

Recommended Uses

Available (but not recommended, see below) for broad-band near-UV imaging.

Special Considerations

NUV-MAMA clear images will be somewhat out of focus because the mirror optimally focuses for use of a filter. Whenever possible, use F25SRF2 or F25QTZ instead of 25MAMA for NUV-MAMA imaging.

For long exposures of faint targets, sky background is likely to be a limiting factor. Observers should consider the use of DARKTIME or (preferably) use the F25QTZ filter, which has nearly the same throughput but rejects geocoronal Lyman- and [O I] 1302+1306 Å air glow.

Users should also consider whether the ACS HRC with the F220W or the F250W filter might be a better choice for their science goals.

Pivot (Å)	FWHM (Å)	AB mag zero point	Speak	B	R80 (arcsec)	Flux in central pixel
2260.6	1209.1	23.994	1.60e+14	1162.5	0.32	8%

Figure 14.23: 25MAMA NUV-MAMA Integrated System Throughput and Redleak


 

Table 14.10: 25MAMA NUV-MAMA Sensitivity & Throughput

	Sensitivity	% Throughput
1200.	7.83E12	0.29
1300.	1.96E13	0.66
1400.	2.96E13	0.93
1500.	3.62E13	1.06
1600.	3.76E13	1.03
1700.	3.98E13	1.03
1800.	4.93E13	1.20
1900.	6.57E13	1.52
2000.	8.95E13	1.96
2100.	1.14E14	2.39
2200.	1.36E14	2.71
2300.	1.48E14	2.82
2400.	1.53E14	2.81
2500.	1.57E14	2.75
2600.	1.59E14	2.69
2700.	1.56E14	2.54
2800.	1.49E14	2.34
2900.	1.23E14	1.86
3000.	9.38E13	1.37
3100.	4.61E13	0.65

Figure 14.24: Point Source S/N vs. V+AB for the 25MAMA NUV-MAMA mode. Top curves are for DARKTIME. Bottom curves are for average sky. Top curves are for DARKTIME. Bottom curves are for average sky. Curves are labeled by required exposure time (sec).


 
Figure 14.25: Extended Source S/N vs. V+AB for the 25MAMA NUV-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 14.11: Radial Profile for 25MAMA*

Radius			Fraction of Energy Encircled
Pix	arcsec	intensity
1	0.024	3.267e-02	0.141
1.5	0.037	2.107e-02	0.236
2	0.049	1.345e-02	0.331
3	0.073	6.141e-03	0.467
4	0.098	2.981e-03	0.557
5	0.122	1.485e-03	0.614
10	0.245	3.377e-04	0.746
15	0.367	1.676e-04	0.834
20	0.490	9.542e-05	0.900
25	0.613	4.543e-05	0.947
30	0.735	2.065e-05	0.972
40	0.980	5.088e-06	0.994

*See STIS ISR 2003-01.

Figure 14.26: Point Source Encircled Energy for 25MAMA NUV-MAMA


 
Figure 14.27: Point Source Intensity vs. Radius for 25MAMA NUV-MAMA