For the first half of the 20th Century, Mount Wilson was the most famous observatory in the world. The biggest telescopes were here, and their new designs were changing the way astronomy was done. Among the many discoveries made on the mountain, a few revolutionized our understanding of our place in the Universe. Here, for the first time, Harlow Shapley measured the size of the Milky Way Galaxy and located our position in it, far from the center. Then Edwin Hubble proved that the mysterious spiral nebulae, which astronomers had speculated about for decades, were in fact distant galaxies similar to our own. Then Hubble teamed up with Milton Humason and discovered that this immense Universe was expanding. Space itself was getting bigger. This finding, when run backwards in time, lead straight to the Big Bang Theory. So this is where modern cosmology began, and thus, in our long search for our origins, Mount Wilson holds a unique place in human history. Today, our original solar and nighttime telescopes, the world’s largest for two generations of astronomers, have been joined by the new CHARA array, which has the highest resolution of any optical or infrared system ever built, achieving unprecedented views of the stars.
One Hundred Years Ago, July 1st, 1917, the 100-Inch Mirror Arrived atop Mount Wilson! Click here to read more.
In 1917, a crew drives an early Mack truck up the Mount Wilson Toll Road, with the precious 100-inch mirror crated and standing vertically in the back. Photo: Carnegie/ Huntington Library
Explore Mount Wilson in Person
- Take a Sat or Sun Guided tour.
- Schedule your own Private Group Tour.
- Free weekend Solar Observing.
- Have lunch at our Cosmic Cafe.
- View through 60-inch or 100-inch telescopes.
Explore Mount Wilson On-Line
- Take a spherical panoramic tour.
- Interactive map and virtual tour of the Observatory’s facilities.
- Learn about the Observatory’s history.
- Watch Huell Howser’s California’s Gold episode on Mount Wilson.
- Watch a 2012 oral history walking tour with Don Nicholson.
- Check out the CHARA Array website.
- Watch videos about CHARA’s cutting-edge technology.
- Look at the latest image of the Observatory from Towercam.
- See today’s sunspot drawing from the 150-ft solar tower.
- Watch Above the Inversion Layer and experience a full revolution of the 100-inch Telescope dome.
Support Mount Wilson Observatory
- Help keep the Observatory operations going and preserve its famous telescopes for future generations, Donate!
- Join the people who keep the Observatory programs going, Volunteer.
- Run the September 16th 5K, a fundraiser to add restrooms, benches, and scenic overlooks to the Observatory.
George Ellery Hale, 1910. Photo: Carnegie/ Huntington Library
The Observatory’s founder, George Ellery Hale, built four telescopes, each one in succession becoming the largest in the world. Here they are shown to the same scale. His first was the 40-inch refractor at Yerkes (in Wisconsin) on the left, but then he began building the more revolutionary–and more compact–reflector telescopes, using a large mirror instead of a lens. His next two are on Mount Wilson, the 60-inch and the 100-inch. (While not quite as grand as his last, these two had the light gathering power for astronomers to discover our place in the expanding Universe.) His fourth, the 200-inch Hale Telescope at Palomar, is represented on the right by one of Russell Porter’s famous cutaway drawings. This image has been reversed and extended on the left side for a better comparison of the relative sizes of the full domes. Hale’s telescopes were the biggest from 1897, when Yerkes opened, to 1993, when the Keck telescope in Hawaii was completed–a span of 96 years. To see these drawings enlarged, click here. Drawing credits: University of Chicago/Yerkes Observatory, Carnegie Observatories, Palomar Observatory/Caltech.
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