Astronomy on Mount Wilson

Before the 200-inch Hale Telescope on Palomar Mountain was completed, the 100-inch Hooker Telescope on Mount Wilson was the world's largest. And before that, the world champion was the 60-inch telescope, also on Mount Wilson.

The big Mount Wilson scopes were put out of business as heavy-duty deep-sky instruments not so much by the construction of the much larger telescope on Palomar as by light pollution from nearby Los Angeles. But taking long-exposure photographs of "faint fuzzies" isn't all that big telescopes are good for. The bigger a telescope's mirror, the smaller the features that it can resolve. If you want to see small features on planets, or split tight double stars, you need a big scope to do the job. You also need steady air, or "good seeing," as astronomers call it. And here Mount Wilson has a natural advantage — by all reports, it has some of the best astronomical seeing in the world. This results from steady on-shore winds lifting ocean-cooled air over the mountain, the same conditions found in Chile, Hawaii, the Canary Islands, and most other sites for major astronomical observatories.

This good seeing allows the big telescopes on Mount Wilson to operate near their theoretical resolving limits on some occasions.…

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