Space Telescope Imaging Spectrograph Instrument Handbook for Cycle 17

CCD Long-Pass Imaging F28X50LP

---

Description

The F28X50LP mode is useful for deep imaging longward of 5500 Å. For a fixed exposure time it can detect point sources roughly as faint as with WFPC2 with the F606W filter, but with higher spatial resolution. The field of view is 28x50". The ACS/WFC with the F814W filter will be more appropriate for most programs.

Recommended Uses

Recommended for deep high-resolution imaging between 5500 Å and 10,000 Å. Default aperture for target acquisitions.

Special Considerations

Very red sources may show significant wings from detector halo (see Section 7.2.7).

Pivot (Å)	FWHM (Å)	AB mag zero point	Speak	B	R80 (arcsec)	Flux in central pixel
7223.4	2693.2	25.266	1.76e+15	3486.8	0.15	14%

Figure 14.7: Throughput for F28x50LP


 

Table 14.4: F28X50LP Sensitivity & Throughput

	Sensitivity	% Throughput
5400.	2.38E14	1.93
5600.	1.19E15	9.32
5800.	1.49E15	11.30
6000.	1.67E15	12.23
6200.	1.70E15	12.05
6400.	1.74E15	11.95
6600.	1.75E15	11.61
6800.	1.66E15	10.71
7000.	1.69E15	10.58
7200.	1.64E15	10.01
7400.	1.60E15	9.47
7600.	1.44E15	8.33
7800.	1.40E15	7.89
8000.	1.28E15	7.04
8200.	1.18E15	6.29
8400.	1.10E15	5.76
8600.	1.00E15	5.11
8800.	1.01E15	5.03
9000.	1.01E15	4.93
9200.	9.76E14	4.66
9400.	9.46E14	4.42
9600.	8.74E14	4.00
9800.	7.19E14	3.22
10000.	5.25E14	2.30

Figure 14.8: Point Source S/N vs. V+AB for the F28X50LP filter. Top curves are for low sky; bottom curves are for average sky. Curves are labeled by required exposure time (sec).


 
Figure 14.9: Extended Source S/N vs. V+AB for the F28X50LP filter for gain=1. Top curves are for a source area of 0.2 arcsec²; bottom curves are for 1 arcsec². Average sky assumed. Curves are labeled by required exposure time (sec).


 

Table 14.5: Radial Profile for F28X50LP

Radius			Fraction of Energy Encircled
Pixels	Arcsec	Intensity
1	0.050	1.703e-02	0.337
1.5	0.075	7.468e-03	0.512
2	0.100	4.196e-03	0.632
3	0.150	1.733e-03	0.804
4	0.200	4.246e-04	0.883
5	0.250	1.660e-04	0.911
10	0.500	2.469e-05	0.976
15	0.750	5.360e-06	0.996
19.25	0.963	3.333e-07	1.000

Figure 14.10: Point Source Encircled Energy for F28X50LP


 
Figure 14.11: Point Source Intensity vs. Radius for F28X50LP