Centennial: Mt. Wilson Observatory's 100-inch Hooker Telescope

Image of the observatory with the historic 100-inch Hooker Reflector Telescope on Mount Wilson in Los Angeles County, California.
(Image Source: Los Angeles Times, Photographer: Francine Orr)

By Glenn A. Walsh

Reporting for SpaceWatchtower

The historic, 100-Inch Hooker Reflector Telescope, at Mount Wilson Observatory in Los Angeles County, California, marks 100 years of discoveries today (November 3). It was the night / early morning of 1917 November 2 to 3 that First Light shone through the Hooker Telescope.

In fact, 100 years ago as of the hour of the posting of this blog-post, 2017 November 3 at 3:00 a.m. Pacific Standard Time (PST) / 7:00 a.m. Eastern Daylight Saving Time (EDT) / 11:00 Coordinated Universal Time (UTC), it is believed to be the time the actual First Light occurred.

[It would be another year before the first Daylight Saving Time would be established in America, due to the United States entry into World War I. Daylight Saving Time proved unpopular to many people, particularly those in the rural areas. Hence Congress repealed Daylight Saving Time shortly after the end of World War I.]

[The international time scale used by scientists, based on the time at the Royal Observatory in Greenwich, London, England, is known as Coordinated Universal Time. At the time the Hooker Telescope began scientific research, this time was known as Greenwich Mean Time (although for Greenwich Mean Time, the day began at Noon).]

Actually, there is some dispute as to the exact time of First Light, and whether it occurred on November 2 or November 3 (or even November 1). The object viewed through the telescope is also in dispute.

The first attempt at First Light seems to have occurred on the evening of November 2, when the telescope was pointed toward Jupiter. However, the image was quite poor, and the astronomers in attendance [George Ellery Hale (first Mount Wilson Observatory Director), Walter S. Adams (second Mount Wilson Observatory Director), George W. Ritchey (also telescope-maker), Francis G. Pease (also designer of the Hooker Telescope), and Ferdinand Ellerman] feared the mirror may be defective (as happened in 1990 after the orbiting of the Hubble Space Telescope).

However, the telescope dome had been open most of the day, for construction workers to finish their work. The scientists decided the observatory interior, including the mirror, was not cool enough for proper observations. So, they agreed to allow the mirror to cool and come back later.

When George Hale and Walter Adams returned at around 3:00 on the morning of November 3, they pointed the new telescope at the bright star Vega (although the star viewed is in dispute). They saw a very sharp image of this celestial object, which is considered the actual First Light.

The dispute in the date of the First Light is due to Walter Adams' later recollection that First Light was on the evening of November 1 to 2, while the diary of George Hale and the post-dated telescope log of night assistant Wendell P. Hoge stated that First Light was on the night of November 2 to 3.

However, most astronomical research did not really get underway until 1918, when the construction of the telescope was completely finished.

Mount Wilson Observatory Director George Ellery Hale was a very ambitious astronomer. By 1908, Mount Wilson Observatory already had the largest, operational telescope in the world, a 60-Inch reflector telescope. A larger 72-Inch reflector telescope, built in 1845 in Parsonstown, Ireland, remained in use until about 1890 and was partly dismantled in 1908.

However, Director Hale was not satisfied. He wanted an even larger telescope. In fact, even before the 60-Inch telescope could be tested, a 4.5-ton disk for the mirror of a 100-Inch telescope had been cast.

A good friend of Director Hale, local businessman John D. Hooker, pledged $45,000 for an 84-Inch (later increased to 100-Inch) glass mirror disk, along with the equipment and facilities to create such a large mirror. Now, Dr. Hale had to find the money (more than $500,000) to build an observatory building to house this new, giant telescope and other needed facilities.

Mr. Hooker's gift only covered 10 per-cent of the total cost of the project. And, the Carnegie Institution of Washington, which owned and operated Mount Wilson Observatory, could not help. Their endowment was needed to maintain their existing research departments.

However, Dr. Hale found an enthusiastic supporter: industrialist and philanthropist Andrew Carnegie, who had created the Carnegie Institution of Washington! Even from his early days as a steel entrepreneur, Andrew Carnegie had greatly appreciated the importance of science and technology.

Mr. Carnegie's science philanthropy had begun in 1895 with the opening of Pittsburgh's Carnegie Museum of Natural History, which he enhanced in 1907 with, what has become, one of the world's best collections of dinosaur skeletons. He had also helped astronomer and telescope-maker John A. Brashear complete a new, 3-dome Allegheny Observatory in Pittsburgh, with all of the steel donated by the Carnegie Steel Company.

Andrew Carnegie had visited Mount Wilson Observatory in 1910 [the same year he donated an 11-Inch Brashear refractor telescope to the Carnegie Institute of Technology in Pittsburgh (today's Carnegie Mellon University), so the students could see Halley's Comet] and had been quite impressed with the 60-Inch reflector telescope. In 1911, Mr. Carnegie donated another $10 million to the Carnegie Institution of Washington. The donation came with a suggestion: “I hope the work at Mount Wilson will be vigorously pushed, because I am so anxious to hear the expected results from it. I should like to be satisfied before I depart, that we are going to repay to the old land some part of the debt we owe them by revealing more clearly than ever to them the new heavens.”

Once completed, the Hooker Telescope did not disappoint. Astronomer Edwin Hubble, for whom the Hubble Space Telescope is named, used the telescope to prove that Andromeda was not just a nebulae in our galaxy as scientists had concluded, but a whole separate galaxy of stars—one of thousands of separate galaxies.

Six years later, Dr. Hubble and Milton Humason used the Hooker Telescope to discover that the Universe is expanding, and they measured the expansion and the size of the Universe. In the 1930s, Fritz Zwicky found evidence for Dark Matter and Seth Nickolson discovered two more Moons of Jupiter (numbers 10 and 11). In the 1940s, Walter Baade used the telescope to find two different types of Cepheid Variable Stars, which led to a new estimate for the size of the Universe, double the estimate Dr. Hubble had calculated.

The 100-Inch Hooker Reflector Telescope was the world's largest reflector telescope from 1917 to 1949. In 1949, the 200-Inch Hale Reflector Telescope at Palomar Observatory in San Diego County, California, named after George Ellery Hale, became the largest telescope in the world.

In the 1980s after ending Mount Wilson Observatory's research program, the institution became a public observatory operated by the Mount Wilson Institute (but still owned by the Carnegie Institution for Science). The Institute sells telescope time to private groups, as well as providing educational tours to local youth groups and to the general public.

Special Thanks: Marilyn E. Morgan, Mount Wilson Observatory.

Internet Links to Additional Information ---

Good photograph of 100-inch Hooker Reflector Telescope:
Link >>> http://spacewatchtower.blogspot.com/2017/11/astronomical-calendar-2017-november.html

100-inch Hooker Reflector Telescope  --
Link 1 >>> http://amazingspace.org/resources/explorations/groundup/lesson/scopes/mt_wilson/
Link 2 >>> https://en.wikipedia.org/wiki/Mount_Wilson_Observatory#Hooker_telescope
Building the Telescope: Link >>> https://www.mtwilson.edu/building-the-100-inch-telescope/

Mount Wilson Observatory, Los Angeles County CA --
Link 1 >>> https://www.mtwilson.edu/
Link 2 >>> https://en.wikipedia.org/wiki/Mount_Wilson_Observatory

Khan, Amina.
"At Mt. Wilson, scientists celebrate 100th birthday of the telescope that revealed the universe."
Los Angeles Times 2017 November 1.
Link >>> http://www.latimes.com/science/la-sci-sn-mt-wilson-centennial-20171101-htmlstory.html

Nicholson, Don and Bob Eklund. "First Light Doubts on Mount Wilson."
Reflections, Mount Wilson Observatory, Mount Wilson Institute. Fall Quarter / 2017 September,
Page 3.
Link >>> http://buhlplanetarium.tripod.com/MtWilson/Reflections_Sept_2017Rev_screenres.pdf

Morgan, Marilyn. "The Amazing Mister Carnegie."
Reflections, Mount Wilson Observatory Association Winter Quarter / 2005 December.
(Includes photo of Andrew Carnegie and George Ellery Hale at Mount Wilson Observatory in 1910 March)
Link >>> http://andrewcarnegie.tripod.com/astro/Reflections-Dec2005.pdf

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
             2017 November 3.

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gaw

Glenn A. Walsh, Project Director, Friends of the Zeiss: < http://buhlplanetarium.tripod.com/fotz/ >
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Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
  < http://www.planetarium.cc >
* Adler Planetarium, Chicago:
  < http://adlerplanetarium.tripod.com >
* Astronomer, Educator, Optician John A. Brashear:
  < http://johnbrashear.tripod.com >
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* Civil War Museum of Andrew Carnegie Free Library:
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* Duquesne Incline cable-car railway, Pittsburgh:
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* Public Transit:
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