Utrecht Echelle Spectrograph (UES)

First light: November 1991. First scheduled observation: February 1992.

De-commissioned: 31 July 2002.

Designed and built by: Institute of Astronomy, Utrecht, under a contract placed by RGO with the Netherlands Foundation for Radio Astronomy. A formal specification was issued in May 1986. The acquisition and guidance unit was constructed at the Kapteyn Institute at Roden.

Description: The Utrecht Echelle Spectrograph (UES) is the principal high-resolution spectrograph for the William Herschel Telescope, and is permanently mounted at one of the f/11 Nasmyth foci. The design is similar from the astronomer's viewpoint to one being produced for the f/36 coudé focus Anglo-Australian Telescope by a team at University College London. This similarity is beneficial in the use of the spectrographs and data reduction as well as in the production phase.

A new UES derotator was commissioned in December 1997. The new derotator has high UV throughput, but a small field of view. The old derotator remains available for long-slit work.

Some scientific highlights:

• Post-AGB stars (1993)
• The best candidate to undergo a supernova explosion (2003)
• William Herschel Telescope Identifies the Companion Star to Type Ia Tycho Brahe's 1572 Supernova (2004)
• First Detection of Rubidium in Asymptotic Giant Branch Stars (2006)
• Diffuse Bands Don't Originate in Circumstellar Envelopes (2008)