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Chris Benn
WHT manager

William Herschel Telescope


Observers can apply for time with the following common-user instruments on the 4.2-m 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 (until end of 2016B only)

Visiting instruments are mounted at the Cassegrain or Nasmyth f/11 foci. Recent visiting instruments include AOLI, CANARY, EXPO, FASTCAM, GHaFaS, INTEGRAL, IQuEye, PLANETPOL, PAUCam, 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 in use at the WHT during a few nights per semester. During these nights, the risk of collisions with the pointing of other telescopes can be queried via the laser traffic control system pages.


2016 September: AF2 will now be available during semester 2017A (INTEGRAL will not).

2016 February: AF2 and INTEGRAL will not be available after the end of 2016B, due to preparatory work for WEAVE (first light expected 2018).

2014 August: As a result of the ongoing rationalisation of instrumentation at the WHT, the adaptive-optics suite (NAOMI/INGRID, NAOMI/OASIS) will not be offered after 31 January 2015, i.e. from 2015A onwards.

2014 February: Azimuth oscillations fixed. These affected many nights during December 2013 - February 2014, but the problem has not been seen since February 24, following replacement of a failing component in the azimuth power amplifier.

2013 August: WHT lower dome shutter is now again operational.

2013 February: Differential tracking with autoguiding is now available, but is not compatible with some dither/nodding scripts (as often used with e.g. LIRIS). Observers interested in dithered, autoguided, observations of a moving target should contact ING.

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Contact:  (WHT Manager)
Last modified: 13 October 2016