Gratings

Below, for each grating mode of STIS, we provide the basic properties of the mode, wavelength ranges covered in each central wavelength setting, sensitivities and throughputs, dispersions and plate scales. Advice on use is provided where appropriate and comparisons of the G230L, G230M MAMA modes with their G230LB, G230MB CCD counterparts are shown.

• First-Order Grating G750L
• First-Order Grating G750M
• First-Order Grating G430L
• First-Order Grating G430M
• First-Order Grating G230LB
• First-Order Grating G230MB
• First-Order Grating G230L
• First-Order Grating G230M
• First-Order Grating G140L
• First-Order Grating G140M
• Echelle Grating E230M
• Echelle Grating E230H
• Echelle Grating E140M
• Echelle Grating E140H
• PRISM

Table 13.1: STMAG as a Function of Wavelength for Stellar Objects. STMAG is defined as the color-dependent correction from V magnitude to STMAG at wavelength .

Spectrum	Wavelength (Å)
	1500	2000	2500	3000	3500	4000	4500	5000	6000	7000	8000	9000	10000
O5 V	-4.80	-3.84	-3.03	-2.35	-1.74	-1.24	-0.77	-0.34	0.41	1.05	1.61	2.10	2.54
B0 V	-4.56	-3.47	-2.77	-2.10	-1.65	-1.20	-0.78	-0.37	0.43	1.03	1.57	2.04	2.48
B5 V	-3.01	-2.02	-1.64	-1.29	-1.00	-1.02	-0.68	-0.30	0.34	0.91	1.38	1.80	2.19
Vega	-0.75	-0.48	-0.13	0.01	0.17	-0.85	-0.60	-0.26	0.33	0.82	1.28	1.81	2.08
A0 V	-0.83	-0.41	-0.02	0.09	0.19	-0.79	-0.59	-0.27	0.31	0.80	1.25	1.58	1.87
A5 V	3.69	0.46	0.82	0.44	0.38	-0.57	-0.50	-0.22	0.27	0.72	1.10	1.40	1.67
F2 V	8.86	2.00	1.66	0.62	0.42	-0.24	-0.28	-0.13	0.17	0.49	0.78	1.04	1.31
F5 V	10.86	3.35	2.03	0.78	0.43	-0.16	-0.23	-0.09	0.13	0.43	0.70	0.96	1.21
G0 V	13.82	5.63	3.32	1.25	0.62	0.13	-0.12	-0.05	0.10	0.29	0.52	0.76	0.98
Sun	10.80	6.02	3.73	1.52	0.69	0.10	-0.11	-0.01	0.07	0.32	0.55	0.82	1.03
K0 V	7.08	6.72	5.13	2.49	1.18	0.53	0.05	0.01	0.01	0.18	0.39	0.61	0.84
M0 V	8.58	8.22	6.64	3.99	2.69	1.80	0.57	0.46	-0.22	-0.39	-0.49	-0.45	-0.38
B0.5 III	-3.86	-2.90	-2.43	-1.88	-1.47	-1.14	-0.71	-0.32	0.39	0.99	1.52	1.98	2.41
A0 III	-1.33	-0.76	-0.24	-0.12	0.05	-0.92	-0.60	-0.28	0.33	0.85	1.32	1.57	1.96
F0 III	8.93	2.09	1.84	0.80	0.51	-0.31	-0.38	-0.18	0.21	0.58	0.92	1.15	1.43
O9.5 I	-4.09	-3.20	-2.59	-2.01	-1.61	-1.19	-0.74	-0.33	0.40	1.02	1.57	2.04	2.48
B0 I	-3.78	-2.91	-2.45	-1.88	-1.48	-1.10	-0.70	-0.31	0.37	0.94	1.43	1.87	2.27
B5 I	-1.86	-1.33	-1.26	-1.11	-0.87	-0.92	-0.58	-0.26	0.31	0.85	1.34	1.63	2.06

.

Table 13.2: STMAG as a Function of Wavelength for Non-Stellar Objects. STMAG is defined as the color-dependent correction from V magnitude to STMAG at wavelength

Spectrum	Wavelength (Å)
	1500	2000	2500	3000	3500	4000	4500	5000	6000	7000	8000	9000	10000
Elliptical	3.35	3.19	4.17	2.92	1.60	0.70	0.17	0.15	-0.04	-0.08	-0.07	-0.13	n/a
S0	4.63	3.95	3.27	2.23	1.61	0.71	0.18	0.13	-0.03	-0.13	-0.02	-0.08	n/a
Sa	2.64	2.27	2.39	1.78	1.31	0.36	0.12	0.07	-0.06	-0.05	-0.00	0.02	n/a
Sb	1.70	2.59	2.04	1.32	1.12	0.43	0.17	0.10	0.02	-0.05	-0.01	-0.04	n/a
Sc	-0.18	0.44	-0.17	-0.68	-0.67	-0.51	-0.44	-1.25	0.18	0.40	n/a	n/a	n/a
Starburst,E(B-V)<0.1	-1.71	-1.15	-0.68	-0.43	-0.13	-0.42	-0.23	-1.24	0.21	0.40	0.70	0.85	n/a
Starburst,0.25<E(B-V)<0.35	-0.95	-0.87	-0.33	-0.10	0.08	-0.19	-0.19	-0.28	0.15	0.44	0.41	0.47	n/a
Starburst,0.51<E(B-V)<0.60	-0.40	-0.18	0.01	0.23	0.03	-0.14	-0.12	-0.36	0.07	0.07	0.18	0.29	n/a
Starburst,0.61<E(B-V)<0.70	0.05	0.31	0.31	0.15	0.27	-0.17	-0.13	-0.11	0.06	0.17	0.26	0.24	n/a

How to Use The STMAG Tables

1. Interpolate in the table to get STMAG for the spectral type and wavelength region of your target observation (e.g. G0 V @ 4300Å).
2. Add the target V magnitude to the STMAG derived from Step 1.
3. Find the S/N plot for the grating you want to use.
4. Locate V+STMAG on the horizontal axis and read off the S/N for the desired exposure time (or read off the exposure time for the desired S/N).