The completed 100-inch telescope dome at Mt. Wilson Observatory, as seen from the 150-foot tower telescope in 1916
The completed 100-inch telescope dome at Mt. Wilson Observatory, as seen from the 150-foot tower telescope in 1916 © Observatories of the Carnegie Institution for Science Collection at the Huntington Library

Wednesday, Nov 1, marks the centennial of the 100-inch Hooker telescope. When it gathered its first light on Nov.1, 1917, it overtook its 60-inch neighbor and became the largest telescope in the world — a position it held for more than three decades.

The Hooker 100-inch reflecting telescope, side view with tube 40 degrees from horizontal. Edwin Hubble's chair, on an elevating platform, is visible at left
The Hooker 100-inch reflecting telescope, side view with tube 40 degrees from horizontal. Edwin Hubble's chair, on an elevating platform, is visible at left © Observatories of the Carnegie Institution for Science Collection at the Huntington Library