Introduction

This manual is intended for observers, support astronomers, and telescope operators who are using or supporting the William Herschel Telescope (WHT) for direct imaging observations with CCD detectors. The WHT provides five instruments which are capable of taking direct images, these are:-

• The Prime Focus Imaging Platform (PFIP), which can take images at the f/2.8 corrected prime focus of the WHT.
• The Auxiliary Port of the Cassegrain A&G box, which can take images at the f/11 Cassegrain focus, via a 45 flat mirror in the A&G box.
• The Taurus Fabry-Perot interferometer, which without its etalons acts as a focal reducer with interchangable f/2.11 and f/3.96 cameras, which can be used for direct imaging at those focal ratios.
• The LDSS low dispersion spectrograph, which without its grisms and masks acts as a focal reducer with an f/2.0 camera, and can take direct images. This arrangement is usually used to provide data for making the masks for LDSS spectroscopic observations.
• The ISIS double-beam spectrograph, in which either of the gratings can be replaced by a flat mirror, allowing direct imaging at the f/3.33 focal ratio of the ISIS cameras. This arrangement is used primarily for imaging polarimetry.

Imaging applications with Taurus, LDSS and ISIS are described in the respective manuals for those instruments. This manual is for users of Prime and Cass Auxiliary focii.

• WHT Prime Focus
  • Prime Focus Optics
  • The Prime Focus Rotator
  • The Prime Focus Instrument Platform
  • Control Electronics
  • Autoguider
• Auxiliary Focus Imaging
  • The Cassegrain A & G Box
  • Autoguider
  • The Auxiliary Focus Filter Unit