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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

Visiting instruments are mounted at the Cassegrain or Nasmyth (GRACE) f/11 foci or at the f/3 prime focus. The enclosure at the Nasmyth focus includes an optical bench. Recent visiting instruments include AOLI, CANARY, EXPO, FASTCAM, GHaFaS, HiPERCAM, PAUCam, PNS, SAURON and ULTRACAM.

AF2, prime-focus imaging and NAOMI (AO) are no longer offered. It's expected that the new wide-field MOS WEAVE will be commissioned at WHT prime focus in late 2019.

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

The median seeing at the WHT is 0.8 arcsec during April - November. 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.


2017 March: The lower dome shutter has been repaired. Observations at elevation < 25 deg will no longer be vignetted by the dome (plot).

2017 February: AF2 and the prime-focus imager (16-arcmin field) will not be available in 2017B.

2017 January: Vignetting at low elevation: the WHT lower dome shutter is currently stuck in a raised position, and observations at elevation < 25 deg will be vignetted (plot).

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.

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.

For older/retired news items, click here.

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Contact:  (WHT Manager)
Last modified: 16 August 2018