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Mount Wilson Observatory

The Hooker Telescope

The Hooker Telescope - vintage postcard
The Hooker Telescope - vintage postcard ca 1920

Mount Wilson Observatory is perched above the Los Angeles basin, above the smog and in a paradoxically ideal location for an observatory. The very inversion layer that traps pollutants in the L.A. basin is also responsible for the best astronomical "seeing" in the continental United States. This excellent "seeing" was appreciated by late 19th century astronomers and in 1904 led George Ellery Hale to build the Mount Wilson Solar Observatory on the site. 1904-1905 also saw the installation of the Snow Telescope - a device for spectroscopic and spectroheliographic studies of the sun and bright stars. In 1907 a 60" reflector telescope was completed and remains operational to this day.

Shortly after installation of the 60", work began on a 100" reflector - the largest mirror telescope attempted at the time. Financing for the mirror was provided by John Hooker with completion funds donated by Andrew Carnegie. The 100" bears John Hooker's name.

The grinding of the mirror and design and construction of the mount, clock drive and dome were daunting tasks. And transporting the parts up the Mount Wilson Toll Road by mule and mule-assisted truck was in itself a combination of ingenuity, brute force and determination. [A good account of the early days of Mount Wilson can be found in Woodbury, David (1939) The Glass Giant of Palomar Dodd, Mead & Co., New York, 368 pgs.]

In 1917 the 100" Hooker Telescope was completed and the term "Solar" was dropped from observatory's name. Many important discoveries were made with the Hooker. Among these, Edwin Hubble revised our understanding of the size of the Universe and found convincing evidence of an expanding universe at the time when Einstein's theories were first being put to the test.

View inside Hooker dome
View of the Hooker Telescope
(mirror at base)
©1999 Gary Fisher
Hooker Telescope - 3-D anaglyph
View of the Hooker Telescope
Anaglyph 3-D Version
©1999 Gary Fisher
requires red -green 3-D glasses

The Hooker remained the largest telescope in the world until 1948 when the 200" Mount Palomar Telescope was put into operation. In 1981 the Hooker Telescope was dedicated as a International Historical Mechanical Engineering Landmark.

Visiting Mount Wilson

Mount Wilson is about 25 miles from La Canada via the Angeles Crest Highway and the five mile Mount Wilson Road (no "toll" fee required). You can visit the observatory seven days a week and even get a look at the 100" Hooker from inside its protective dome.

At the terminus of the Mount Wilson Road and immediately before entering the observatory grounds you will pass a forest of transmitting and relay antennas that beam TV and radio signals to the Los Angeles basin below. I am always struck by the strangely sci-fi movie appearance of these antennas which rise above small unmanned transmitter and relay buildings jammed with electronics and humming with the sound of cooling fans.

Enter the observatory grounds and park in an overly-large lot below the modern visitor's center. Then take a short hike along an access road and back into history. Along the way you will find a small one-room exhibit building with vintage rear-illuminated celestial photos taken at Mount Wilson over the years; it's worth taking in. To the right of the exhibit building you'll see the 150 foot Snow Telescope. Walking further you will pass the 60" Telescope. Then cross a modern suspension bridge leading to the Hooker which rises majestically above the surrounding pines. Follow the path to the visitor entrance to the dome and climb a couple of flights of narrow steps in a submarine-like metal-sheathed stairway to the glass-windowed observation room. Through the windows you'll see the Hooker Telescope looming massively before you. In the dim light it has a compelling, mechanistic beauty. You can even see the chair that Hubble sat in for many cold nights while steering the giant telescope and exposing his hypersensitized plates.

After leaving the Hooker, take the short hike out to Echo Point for a panoramic view of the San Gabriel Mountains, the Los Angeles basin and, of course, the Hooker Telescope.

Panorama from Echo Point
©1999 Gary Fisher
drag picture with your mouse

Today, Mount Wilson is entering a new era. It is the home of Georgia State University's CHARA Telescope Array. CHARA stands for Center for High Angular Resolution Astronomy. While still under construction, the array when completed will consist of six telescopes within a 1300 foot circle with vacuum pipes bringing the light from each telescope to a central combining building. The result will be a telescope which can resolve detail equivalent to a single telescope 1300 feet in diameter! At the time of this writing (late 1999) you can see several of the telescopes that have already been installed. The CHARA array is scheduled to be operational in early 2001.

one telescope in the array
One Telescope in the Array - tree shows scale
©1999 Gary Fisher

text and photographs © 1999 Gary Fisher

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