System Efficiency

The quantum efficiency of the Loral 1K measured in the lab is given in Table 7 and shown in Figure 6. Also given is the quantum efficiency for the GEC CCD that the Loral 1K replaced; the Loral 1K offers a 2-$3 \times$ gain in quantum efficiency over the GEC at most wavelengths.

  

Figure 6: Quantum efficiency curves for the Loral 1K and GEC CCDs

 

 

Table 7: Quantum efficiency of the Loral 1K and GEC CCDs

Wavelength	Quantum Efficiency
(Å)	(%)
	Loral 1K	GEC
3000	25	20
3500	48	19
4000	65	17
5000	83	22
6000	93	35
7000	91	45
8000	83	30
9000	59	14
10000	10	3

Efficiency measurements of the complete telescope/spectrograph/CCD combination using observations of spectrophotometric standard stars were obtained with gratings 09 and 32 on engineering nights in 1995 November. The results are given in the Table 8 and Figure 7 in terms of the percentage of photons striking the telescope primary mirror which are eventually detected. Also given in Table 8 and Figure 7 are the estimated efficiencies for gratings 11 and 13 that are obtained by scaling the measured system efficiencies with the GEC CCD by the ratio of the Loral and GEC quantum efficiencies.

  

Figure 7: System efficiency curves for gratings 09, 11, 13 and 32

 

 

Table 8: System Efficiency of the 1.5-Meter Cassegrain Spectrograph with Gratings 09, 32, 11 and 13

Wavelength	System Efficiency
(Å)	(%)
	09	32	11	13
3000			0.0	1.4
3500	7.5		0.5	4.0
4000	13.5		3.4	7.6
4500	16.5
5000	17.0		8.3	10.2
5500	16.0
6000	13.5		18.6	13.0
6500	10.0	14.8
7000		13.6	12.9	7.3
7500		11.8
8000		8.5	9.9	5.5
8500		6.5
9000		5.0	6.3	2.9
9500		2.9
10000			1.3	0.0