Hooker Telescope, 100-inch telescope at Mount Wilson Observatory in California, US

The Hooker Telescope is a reflector telescope with a 100-inch primary mirror located on Mount Wilson in California. The instrument sits on a mechanical support system with a mercury flotation bearing that distributes its enormous weight and allows it to point anywhere in the sky.

George Hale persuaded John Hooker to fund a 2.54-metre mirror and the Carnegie Institution of Washington to supply the mount; the telescope was inaugurated on Mount Wilson in 1917. It remained the world's largest telescope for thirty years, until the five-metre instrument at Palomar took the title. In 1920 Edwin Hubble used it to find variable stars in the Andromeda nebula M31, showing it was a galaxy beyond the Milky Way.

The telescope's name honours John Hooker, the bureaucrat who paid for its 2.54-metre mirror, while the mount came from the Carnegie Institution of Washington. Edwin Hubble used the instrument in 1920 to find variable stars in the Andromeda Nebula M31, showing it was a galaxy beyond the Milky Way. The observatory on Mount Wilson keeps the instrument as a working historic site.

The telescope sits at an elevation of about 5,710 feet, so visitors should prepare for cooler temperatures and thinner air. Planning a visit here means dressing warmly and arriving ready for mountain conditions.

The mirror is held by 36 adjustable pressure points that keep it perfectly aligned no matter how the telescope rotates. This clever engineering lets the enormous mirror distribute its weight evenly while maintaining the precision needed for sharp observations.