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
• AF2/WYFFOS - multi-object fibre-fed spectroscopy, R < 3000, 40' field
• NAOMI/OASIS - integral-field spectroscopy with or without adaptive optics (AO), R < 4000, 17" field
• NAOMI/INGRID - IR imaging with or without AO, 40" field (coronagraphy is also possible, with OSCA, 25" field)
• LIRIS - IR spectroscopy, R < 4000, and imaging, 4' field
• prime-focus - optical imaging, 16' field
• auxiliary port - optical imaging, 1.8' field

Visiting instruments are mounted at the Cassegrain or Nasmyth f/11 foci. Recent visiting instruments include CIRPASS, INTEGRAL, PLANETPOL, PNS, SAURON, S-CAM 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.

Development work at the WHT is currently focussed on the AO suite (NAOMI, OASIS, INGRID), and on provision of a Rayleigh laser guide star ( GLAS, first light expected late 2006), which will allow AO observations almost anywhere on the northern sky.

The median seeing at the WHT is 0.7 arcsec. The sky brightness is similar to that at other good dark sites, V = 21.9 mag arcsec².

See the ING astronomy, PR, and home pages for other information. Useful links: documentation, the ING newsletter, La Palma technical notes, fault reporting, the service programme, overrides, the data archive, observation logs, ING staff list, weather, La Palma, instrumentation directory, list of useful links.