Lick Observatory and Lowell Observatory in Flagstaff, Ariz., which opened in 1894, both remain active in astronomical research. Other historic observatories now focus primarily on public outreach and education, including Yerkes Observatory (1897) in Williams Bay, Wis., and Mount Wilson Observatory (1904), outside Pasadena, Calif. At each of these sites, you can step into the history of the cosmos — experiencing the deep time of the stars, as well as more recent histories of discovery. Looking through 19th-century glass at the Lick, you can see where E. E. Barnard spotted a new moon of Jupiter and James Keeler found a gap in Saturn’s rings. At Mount Wilson, Edwin Hubble, building on work done by Henrietta Swan Leavitt at Harvard, made an observation that proved there were other galaxies in the universe beyond the Milky Way. At Yerkes, you can peer through the 40-inch refracting telescope that surpassed Lick’s in size in 1897 and was used by a cadre of path-breaking women working in astronomy.

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Persons: Barnard, James Keeler, Mount Wilson, Edwin Hubble, Henrietta Swan Leavitt Organizations: Lowell, Yerkes Observatory, Mount Wilson Observatory, Harvard, Yerkes Locations: Lick, Flagstaff, Ariz, Williams Bay, Wis, Pasadena, Calif, Mount