Hale Telescope at the Palomar Observatory

This week marks the 75th anniversary of "first light" on the 200 inch (5 meter) Hale Telescope at Palomar Observatory, on 26 January 1949. At that moment, the 200 inch telescope eclipsed the 100 inch Hooker Telescope, at Mt. Wilson Observatory, as the largest telescope in the world.

The driving force behind the creation of both telescopes (and indeed both observatories) was American physicist & astronomer George Ellery Hale [1868-1938], principal architect of the modern science & technology of astrophysics. Hale had been responsible for the three largest & most productive telescopes, before the 200-inch: the 40 inch (1 meter) refractor at Yerkes Observatory (1897-1908) [see footnote], the 60 inch reflecting telescope at Mt. Wilson Observatory (1908-1917), as well as the 100 inch Hooker telescope (1917-1949).

In 1976 the Soviet Union completed the 6 meter (236 inch) BTA-6, which then technically became the world's largest optical astronomical telescope. But it was poorly made & poorly sited, such that for imagery, the 200 inch Hale Telescope remained in effect the world's highest quality optical astronomical telescope until 1993, when the first 10 meter Keck Telescope opened in Hawaii.

So, in effect, and including the 200 inch Hale Telescope, George Ellery Hale was responsible for the world's largest optical astronomical telescope, or the world's most effective optical astronomical telescope, from 1897 to 1993.

The 200-inch Hale telescope continued the tradition of advancing the frontiers of astronomy, astrophysics & cosmology, seeing deeper into the universe than any of its predecessors. It played a key role in correcting the distance scale used earlier by Harlow Shapley [1885-1972] & Edwin Hubble [1889-1953], in their discoveries of the Milky Way galaxy, and the universe itself, during the first 3 decades of the 20th century. The Hale telescope was also used to identify the optical counterparts for the newly discovered quasi-stellar objects (quasars or QSOs). The 200-inch Hale telescope, and Palomar Observatory, remain active in astronomical research today.

Footnote: Although the 40-inch Yerkes refractor is commonly accepted as the world’s largest telescope, it was not. The Great Melbourne Telescope (the GMT of its day), a 48-inch speculum mirror, cassegrain reflector, completed in 1869, was in active use at the time. But it was an inferior telescope, for various reasons, and is now almost forgotten in astronomical history. George Ritchey, famous for his work at Yerkes & Mt. Wilson, and as a creator of Ritchey-Chretien optics, lamented that the GMT had set astronomy back 50 years. Some remnants of the old GMT were destroyed in the disastrous brush-fire that stormed through Mt. Stromlo Observatory in 2003. There is now a multi-organization project to restore the old GMT and return it to its original site at the Melbourne Observatory (see link below).

The photo of the Hale Telescope comes from Caltech & Palomar Observatory. The caption reads: “The Hale Telescope from the east. Notice the ‘cage’ under the mirror cell that houses instruments used at the telescope's Cassegrain focus. (Palomar/Caltech)”. The primary mirror is at the bottom of the vertical optical truss assembly. The yoke mount, with supports at top & bottom, is an improved version of the English yoke mount used for the 100-inch Hooker telescope, at Mount Wilson Observatory. The yoke (angled from lower left to upper right in the photo) is parallel to the rotation axis of the Earth, which allows for easier tracking of the sky as it moves, relative to the telescope.

The drawing is an original from Russell Porter. The caption reads: “Meridian cross-sectional drawing of the 200-inch Hale Telescope and dome by Russell W. Porter. White lines indicate the light path for an observer or instruments placed at the prime focus (top of the telescope) and at the coudé focus (lower left along the telescope’s polar axis). The labels identify the telescope’s main features. (Palomar/Caltech/Caltech Archives)”.

The third image shows Hubble’s Variable Nebula (NGC 2261). The image here is the first light image for the Hale Telescope, exposed on the night of 26 January 1949, by Edwin Hubble [1889-1953], from the prime focus cage. NGC 2261 is about 2500 light years away, and is likely variable due to dust clouds near the illuminating star, R Monocerotis.

This original post is from Tim Thompson, NASA Senior Astronomer (Retired)

https://en.wikipedia.org/wiki/Hale_telescope  (200-inch Hale Telescope - Wikipedia)

https://sites.astro.caltech.edu/.../telescopes/hale.html   (“The 200-inch (5.1-meter) Hale Telescope”; Photo & drawing source - Palomar Observatory, Caltech)

https://whatson.cmog.org/.../mirror-discovery-200-inch...  (The 200-inch disk - Corning Museum of Glass)

https://hdl.huntington.org/.../collec.../p15150coll7/id/4333  (“First Photographs with the 200-inch Hale Telescope”, 5-page typed document by Edwin Hubble - Huntington Library)

http://scihi.org/hale-telescope/  (“The Hale Telescope at Palomar Observatory” - SciHi Blog, 26 January 2020)

https://en.wikipedia.org/wiki/Palomar_Observatory  (Palomar Observatory - Wikipedia)

https://sites.astro.caltech.edu/palomar/homepage.html  (Palomar Observatory, Caltech)

https://www.newworldencyclopedia.org/.../Mount_Palomar...  (Mount Palomar Observatory - New World Encyclopedia)

https://en.wikipedia.org/wiki/George_Ellery_Hale  (George Ellery Hale - Wikipedia)

https://en.wikipedia.org/wiki/Great_Melbourne_Telescope  (Great Melbourne Telescope - Wikipedia)

https://greatmelbournetelescopeorgau.wordpress.com/  (Great Melbourne Telescope Restoration Project)

https://en.wikipedia.org/wiki/NGC_2261  (Hubble’s Variable Nebula, NGC 2261 - Wikipedia)