William Herschel Telescope
Willam Herschel Telescope at the Observatory Roque de Los Muchachos in La Palma

The William Herschel Telescope (WHT) is the second largest telescope of Roque de Los Muchachos in La Palma. With a primary mirror of 4.2 m in diameter it is also the second largest telescope in Europe only after the Gran  Telescopio de Canarias (primary mirror 10.4 m). At present this telescope is of modest size, nevertheless remains one of the most productive in scientific publications of the world. It has a f2.8 focal ratio and is Cassegrain-Nasmyth type.
The William Herschel telescope can be visited at concerted visits. To book a visit to the Observatory: Visits.



The UK’s Science and Engineering Research Council (SERC) began planning the telescope in 1974 with a final budget of 10 million pounds. In 1981, 20% of the SERC negotiated a 20% stake with Holland, so the telescope belongs to the United Kingdom and the rest to the Netherlands. The first light of the telescope was on June 1, 1981 using the instrument TAURUS-2.


The most outstanding results extracted with data obtained in this telescope are:
* The discovery of the first evidence of a supermassive black hole (Sgr A*) in the center of the Milky Way.
* The first optical observation of a gamma ray burst



* The telescope takes the name of the astronomer William Herschel (Germany 1738 – England 1822), a musician without scientific formation who began his interest in the astronomy to the 35 years of age. This astronomer discovered the planet Uranus with a 1.2m reflecting telescope that built the same along with his sister since he could not afford to buy a refractor telescope of similar size to the use at the time. Herschel was also a pioneer in the design of the azimuth mount that is now used in telescopes like the WHT. In 1981, with the first light of the telescope, was the bicentennial of the discovery of Uranus, hence the telescope bears the name of William Herschel.

* The WHT is like a Swiss Army Knife. In each focus an instrument is placed and in turn has several instruments interchangeable with each other with relative ease. Currently professional astronomers can request observation time for the following instruments:


    • ISIS – espectrograph
    • LIRIS – infrarred espectrograph
    • ACAM – ccd camera and low resolution spectroscopy
    • AF2/WYFFOS – multiobject espectroscopy
    • NAOMI/OASIS – espectroscopy
    • Adaptative optics
    • NAOMI/INGRID – infrarred imaging


More about the other telescopes at the Observatory Roque de Los Muchachos can be found on the official website of the Observatory or at Telescopio Nazionale Galileo and Gran Telescopio de Canarias.


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