e.g. for aluminising) are all incorporated. The size and shape of the shutter allow observations down to 12° above the horizon, which corresponds to an airmass of 4.8. The total moving mass of the dome is , which is mounted on top of a three-storey cylindrical building. The dome was designed to minimise wind stresses and can support up to its own weight again in ice during inclement weather. The dome and telescope rest on separate sets of foundations (driven down into the volcanic basalt), to prevent vibrations caused by dome rotation or wind stresses on the building affecting the telescope pointing. Attached to the dome is a three-storey rectangular building which houses the telescope control room, computer room, kitchen etc. Almost no human presence is required inside the dome, which means the environmental conditions can be kept very stable. As a result, the WHT obtains perfect dome seeing. This building also houses a detector laboratory and a realuminising plant. Because the WHT has the largest single mirror at the Roque de los Muchachos Observatory, its realuminising plant has a vacuum vessel large enough to accommodate the mirrors from any other telescope on the mountain. As a result, all of the other telescopes at the observatory contract to use the WHT plant for their realuminising (with the exception of the Gran Telescopio Canarias, which has its own plant). Operations The WHT is operated by the Isaac Newton Group of Telescopes (ING), together with the 2.5m Isaac Newton Telescope and 1.0m Jacobus Kapteyn Telescope. Offices and administration are located an hour's drive away in Santa Cruz de La Palma, the island's capital. Funding is provided by the UK's Science and Technology Facilities Council (STFC, 65%), the Netherlands' Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO, 25%) and Spain's Instituto de Astrofísica de Canarias (IAC, 10%) (2008 values). Telescope time is distributed in proportion to this funding, although Spain receives an additional 20% allocation in return for use of the observatory site. Five percent of observing time is further reserved for astronomers of other nationalities. As a competitive research telescope, the WHT is heavily oversubscribed, typically receiving applications for three to four times as much observing time as is actually available. The vast majority of observations are carried out in visitor mode i.e. with the investigating astronomer physically present at the telescope. A shift to service mode operations (those carried out by observatory staff