Anglo-Australian Observatory

AAOmega Grating Calculator

Mode: Grating: Order:
Calculate angles from wavelengths
Central wavelength (Å): Blaze wavelength (Å):
Calculate wavelengths from angles
Grating Angle (°): Camera Angle (°):

Both grating and camera angles are remotely adjustable. The blaze (peak grating efficiency) wavelength can be altered by slightly changing the grating angle. The wavelength coverage on the detector is determined primarily by the camera angle, with weaker dependence on the grating angle.

Because of slit curvature, the wavelength coverage, dispersion and resolution all vary between central and outer fibres. The dispersion also increases with wavelength; the dimensionless resolution (l/dl) increases more strongly with wavelength.
Most of the gratings are deliberately `slanted', meaning that the fringes are tilted within the grating (like a venetian blind). The reason is to avoid a 0th-order ghost that would otherwise lie in the middle of the detector when used in Littrow.
Spectrograph numbers: camera focal length is 247mm. Demagnification is 0.413 . Allowed grating angles are 0-49° ; allowed camera angles are 0-94.3° (blue arm) or 0-95.3° (red arm) . There are 2048 spectral x 4096 spatial 15um pixels. Dichroic crossover wavelength is 5700Å .

For further information see The AAOmega web pages

Questions or Comments? Please contact the AAOmega team

Adapted from the TTF Web page originally developed byPaul Markham