HERMES is a four channel fibre-fed spectrograph with high resolution and multi-object capability. It provides a nominal spectral resolution of R~28,000, and an option of higher resolution of R~50,000 using a slit-mask at the cost of approximately 50% light loss. HERMES provides simultaneous observations in the following fixed optical bands:
Blue: 471.5 - 490.0 nm
Green: 564.9 - 587.3 nm
Red: 647.8 - 673.7 nm
IR: 758.5 - 788.7 nm
The HERMES system is built upon the AAT’s existing Two-Degree Field (2dF) optical fibre positioner. The Two Degree Field system ("2dF") is the AAT's most complex astronomical instrument. It is designed to allow the acquisition of up to 392 simultaneous spectra of objects anywhere within a two degree field on the sky. It consists of a wide-field corrector, an atmospheric dispersion compensator and a robot gantry which positions optical fibres to 0.3 arcseconds on the sky. A tumbling mechanism with two field plates allows the next field to be configured while the current field is being observed.