William Herschel Telescope

ISIS - single-slit spectroscopy, R < 10000, 4' slit, spectro-polarimetry
LIRIS - IR spectroscopy, R < 4000, and imaging (including imaging polarimetry), 4' field
ACAM - optical imaging, low-resolution spectroscopy, 8' field
Prime-focus imager - optical imaging, 16' field
AF2/WYFFOS - multi-object fibre-fed spectroscopy, R < 9000, 40' field
NAOMI/OASIS - integral-field spectroscopy with or without natural-guide-star adaptive optics (NGS AO), R < 4000, 17" field
NAOMI/INGRID - IR imaging with or without NGS AO, 40" field (coronagraphy is also possible, with OSCA, 25" field)

Visiting instruments are mounted at the Cassegrain or Nasmyth f/11 foci. Recent visiting instruments include CANARY, EXPO, FASTCAM, GHaFaS, INTEGRAL, PLANETPOL, PNS, SAURON, SPIFS, TRIFFID and ULTRACAM. The enclosure at the spare Nasmyth focus includes an optical bench, and can be used for experimental work, e.g. for instruments requiring mechanical stability.

Targets with significant proper motion (e.g. comets) can be observed with differential tracking.

The median seeing at the WHT is 0.7 arcsec. The dark-of-moon sky brightness at high ecliptic latitude is similar to that at other good dark sites, V ~ 21.9 mag arcsec².

The CANARY laser guide star is currently in use at the WHT during a few nights per semester (May 23-25, July 17-19, 22-24 and July 17-19 in 2013A). During these nights, the risk of collisions with the pointing of other telescopes can be queried via the laser traffic control system pages.

News:
2013 February: Differential tracking with autoguiding is now available, but is not compatible with some dither/nodding scripts. Observers interested in dithered, autoguided, observations of a moving target should contact ING.
2013 January: Vignetting at low elevation: the WHT lower dome shutter is currently (and probably until July 2013) out of action, and observations at elevation < 25 deg will be vignetted (plot).