The Yapp 36-inch reflecting telescope situated in Dome B is open to the public during the day. Learn more about it on one of our telescope tours.
Built in 1932 by Grubb Parsons of Newcastle-upon Tyne at a cost of about £15,000 (including the dome), the 36-inch reflector was a
gift from Mr William Yapp, a prominent industrialist. The telescope was moved to Herstmonceux in 1958 after 21 years of service in Greenwich, where it had been the largest working telescope.
There is a large concave mirror - the primary mirror - at the bottom of the telescope, facing upwards. Light from the stars falls onto this large mirror and is bounced back up the tube where a smaller mirror near the top reflects this light back through the a hole in the centre of the main mirror. The primary mirror aperture measures 91cm with a focal length of 4.6m and a cassegrain focus of f/15.
This telescope was used for astronomical research - mainly stellar spectroscopy and photometry - and later as a test bed for equipment developed for use elsewhere, particularly the Isaac Newton telescope, installed at Herstmonceux in 1967. Astronomers used this telescope mainly to find out about individual stars.
