NUV Grating G285M

Description

The G285M grating samples wavelengths between about 2500 and 3200 Å. The grating has 17 central wavelength settings.

Special Considerations

G285M spectra consist of three 41-Å stripes separated by two 74-Å gaps. To acquire a complete spectrum requires the use of eight central-wavelength settings.

 

Grating	Resolving Power R = λ/Δλ	Dispersion (mÅ pixel–1)	Spatial Resolution (milliarcsec pixel-1)	Plate Scale (milliarcsec pixel-1)		FP-POS Step (Å step-1)
				Disp. Axis	Cross-Disp. Axis
G285M	20,000 - 24,000	40	56 ± 1	24.3	24.4	2.1

Figure 13.22: Wavelength Ranges for the G285M Grating

Dark lines represent wavelengths sampled by all four FP-POS positions.

G285M Point-Source Sensitivity

Table 13.10: G285M Point-Source Sensitivity for PSA

Wavelength (Å)	Throughput	Sensitivity (counts pixel-1 sec-1 per erg cm-2 sec-1 Å-1)	Effective Area (cm2)
2500	4.206E-03	9.7E+11	1.90E+02
2600	4.859E-03	1.2E+12	2.20E+02
2700	5.060E-03	1.3E+12	2.29E+02
2800	4.697E-03	1.2E+12	2.12E+02
2900	4.165E-03	1.1E+12	1.88E+02
3000	3.186E-03	8.8E+11	1.44E+02
3100	2.002E-03	5.7E+11	9.06E+01
3200	1.033E-03	3.1E+11	4.67E+01

Figure 13.23: G285M Point-Source Sensitivity for PSA and BOA

G285M Signal-to-Noise Ratio

Figure 13.24: Point-Source Signal-to-Noise as a Function of STMAG for G285M

The top axis displays constant Fλ values corresponding to the STMAG units (V+STMAGλ) on the bottom axis. Recall that STMAG = 0 is equivalent to Fλ = 3.63E-9 erg cm-2 s-1 Å-1. Colors refer to exposure times in seconds. The edge of the shaded area corresponds to the bright-object screening limit. Use of the PSA is assumed.