Crossley telescope

Lore & Background

The Crossley telescope was given to Lick Observatory in 1895 by British politician Edward Crossley. It was rebuilt from the ground up because its original mounting was very flimsy. The mirror and some initial mounts came from the 36-inch reflector originally mounted in Andrew Ainslie Common's backyard Ealing observatory, where Common used it from 1879 to 1886 to prove the concept of long exposure astrophotography. Common sold the telescope to Crossley, who set it up in Halifax, England in a new dome. Lick Observatory's first director, Edward S. Holden, learned that Crossley wanted to sell the well-regarded Common 36-inch telescope, and after exchanging letters, Crossley formally telegraphed in April 1895 that he would donate the telescope. Funds were raised to ship it to California, including donated services such as The Southern Pacific Company shipping heavy parts at no cost, a service valued at over US$1,000 at the time. Observations by Lick Director James Edward Keeler helped establish large reflecting telescopes with metal-coated glass mirrors as astronomically useful. In 1898 Keeler became director and used the Crossley to take a series of photographs of spiral nebulae, later identified as other galaxies. After Keeler died in 1900, Charles Dillon Perrine took charge of the Crossley, completing Keeler's photography and significantly reconstructing the telescope from 1902 to 1905. Perrine used the rebuilt Crossley to discover eight comets and the sixth and seventh moons of Jupiter. In the 1930s, the Crossley mirror was tested with vapor-deposited aluminum for reflection, and was aluminized in 1934, 1938, 1946, and 1951. Nicholas Mayall added a slitless spectrograph to extend its usefulness.

Reader's Guide

The Crossley telescope was notable for being the largest glass reflecting telescope in the United States for several years after its recommissioning in California. Lick Director James Edward Keeler remarked in 1900 that it was 'by far the most effective instrument in the Observatory for certain class of astronomical work.' Its observations helped establish large reflecting telescopes with metal-coated glass mirrors as astronomically useful, foreshadowing the success of large reflectors in the 1900s. Keeler used it to photograph spiral nebulae, observing that they outnumbered all other hazy objects detectable at that time. Charles Dillon Perrine used the rebuilt Crossley to discover eight comets and the sixth and seventh moons of Jupiter, and its effectiveness influenced his later establishment of a 60-inch reflecting telescope program in Argentina. The telescope was used until 2010 in the search for extra-solar planets, but was taken out of service due to budget cuts. Its legacy includes pioneering long-exposure astrophotography, early nebular photography, and contributions to the detection of exoplanets.

Did You Know?

• The Crossley telescope was originally built by Andrew Ainslie Common and used from 1879 to 1886 to prove the concept of long exposure astrophotography.
• James Edward Keeler used the Crossley to photograph spiral nebulae that were later identified as other galaxies.
• Charles Dillon Perrine discovered eight comets and the sixth and seventh moons of Jupiter using the rebuilt Crossley.
• The telescope was last used in 2010 in the search for extra-solar planets.