AAOmega Grating Information

Grating Set

The full grating set now ordered is given in the table below. The aim is to allow simultaneous low dispersion use from 370nm-880nm; and to allow medium (R~3500) and high (R~8000) dispersion use over the whole wavelength range 370nm-950nm; and to do this with the minimum number of gratings. For IFU use, multiply all resolutions by 1.62 .

Name	Blaze	Wavelengths	Bandwidth	Angle	Dispersion	MOS Resolution
	nm	nm	nm	Degrees	nm/pix	R
580V	450	370 to 580	210	8	0.1	1300
385R	700	560 to 880	320	8	0.16	1300
1500B	400	370 to 450	80	18	0.038	3000
1500V	475	425 to 600	80	20 - 25	0.037	3700
1000R	675	550 to 900	120	18 - 25	0.057	3400
3200B	400	360 to 450	30	37.5 - 45	0.014	8000
2500V	500	450 to 580	40	37.5 - 45	0.018	8000
2000R	650	580 to 725	50	37.5 - 45	0.023	8000
1600I	860	725 to 950	60	37.5 - 45	0.028	8000
1700I	860	845 to 870	30	47	0.024	10000

One of the advantages of VPH gratings is that their peak efficiency (or blaze) wavelength can be altered by changing the grating angle. Some of the gratings are designed for use at a fixed angle, while others are designed to work at a variety of blazes to give full potential wavelength coverage at the desired resolution. When used at non-superblaze angles, the resolution changes as tan of the camera angle. The 1700I grating is a Dickson (or Baldry type-C) grating, with very high efficiency and dispersion, at the expense of fixed grating angle and hence wavelength coverage. The actual performance of the first delivered AAOmega grating is shown below.

First order throughput of delivered test Ralcon grating. The grating angle (+90°) is on the RHS. The grating was uncoated; MgF/solgel coating will increase the efficiciency by ~7%. The wavelength coverage on the CCD is 75 nm.