A faint object spectrograph for the William Herschel telescope
Open Access
- 1 May 1989
- journal article
- Published by Oxford University Press (OUP) in Monthly Notices of the Royal Astronomical Society
- Vol. 238 (2) , 603-619
- https://doi.org/10.1093/mnras/238.2.603
Abstract
This paper describes the Faint Object Spectrograph (FOS-2) recently commissioned on the 4.2-m William Herschel Telescope (WHT) of the Observatorio del Roque de los Muchachos, La Palma. The instrument is optimized for observations of faint objects which would not normally be attempted with general-purpose spectrographs. The collimatorless design offers high efficiency with a very large spectral range obtained from two cross-dispersed spectral orders. The dispersion is 8.7 Å pixel−1 in first order and 4.3 Å pixel−1 in second order with a resolution of 1.5 pixels (33 μm) FWHM. The total efficiency (including losses in the atmosphere) peaks at 16 per cent at 7000 Å and is greater than 1 per cent over the wavelength range 4000–9700 Å. We describe the design and performance of the spectrograph and show examples of data obtained during the first commissioning run in 1987 October. A comparison is made with an earlier spectrograph of this type.Keywords
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