Low Dispersion Survey Spectrograph (LDSS-2)

First light: March 1992. First scheduled observation: August 1992.

Last commissioning: June 1999.

Designed and built by: Durham University and RGO.

Description: The Low Dispersion Survey Spectrograph (LDSS-2), mounted at the Cassegrain focus of the WHT, is a system designed to obtain spectra of objects lying in the apparent magnitude range 20 to 23. In the case of these faint objects one requires a spectrograph of high efficiency avoiding light losses that occur in fibre feeds. The LDSS system is a focal reducer providing a collimated space where grisms of different dispersion may be placed. A focal plane mask is used to isolate the objects to be studied together with regions of night sky, and multiple spectra may be recorded on a CCD.

Some scientific highlights:

• A gravitationally lensed z=2.515 star-forming galaxy (1996)