First-Order Grating G230L

Description

The G230L grating is used with the NUV-MAMA and has a relatively high throughput and a resolving power of ~500.

Recommended Uses

G230L is designed for observations where high spectral resolution is not required, but efficient, spatially resolved spectroscopy with full spectral coverage in the NUV is desired.

Special Considerations

Notice that the CCD G230LB grating mode also covers the NUV with comparable resolution; see Comparison of G230LB and G230L for a detailed comparison of these two grating modes in that wavelength regime.
 

Grating

Spectral Range

Average
Dispersion
(Å per Pixel)

Plate Scale
(arcsec/pixel)

Tilts

Central
Wavelengths

Complete

Per Tilt

G230L

1570–3180

1616

1.58

0.025

Prime

2376

Figure 13.30: Wavelength Range for the G230L Grating Setting.


G230L Sensitivities


Table 13.9: G230L Sensitivities & Throughputs for a Point Source.

λ

Sensitivity

% Throughput

1600

2.4E12

0.0

1700

2.2E13

0.4

1800

4.1E13

0.6

1900

5.9E13

0.8

2000

7.9E13

1.1

2100

1.1E14

1.4

2200

1.3E14

1.6

2300

1.5E14

1.8

2400

1.6E14

1.8

2500

1.7E14

1.8

2600

1.8E14

1.9

2700

1.7E14

1.8

2800

1.6E14

1.6

2900

1.4E14

1.3

3000

1.0E14

0.9

3100

6.0E13

0.5

Figure 13.31: G230L Point Source (left axis), and Diffuse Source (right axis) Sensitivities.


Note:

Point source sensitivity assumes full transmission (zero slit losses). Diffuse source sensitivity assumes a 0.1" wide slit. To convert point source sensitivities to diffuse source sensitivities multiply the point source values by the grating spatial (cross dispersion) plate scale in units of arcseconds per pixel and by the width of the desired slit in units of arcseconds.

G230L Signal-to-Noise

Note:

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/cm2/s/Å. The curves are labeled with exposure times in seconds.



Figure 13.32: Diffuse Source Signal-to-Noise as a Function of STMAG for G230L. 


Figure 13.33: Point Source Signal-to-Noise as a Function of STMAG for G230L.