One of 41 bromide prints related to and showing various stages in the construction of the Hooker 100-inch reflecting telescope at Mount Wilson, California. This view shows the mirror at the early grinding stage in the optical workshop.

This photograph, one of a series, shows the machine used to grind and polish the mirror used on the Hooker telescope. The reflecting telescope with its 100-inch glass mirror was the largest instrument of its type when completed in 1917. The brainchild of George Ellery Hale it is located at over 5,000 feet overlooking the city of Los Angeles. Although light pollution from the encroaching city has degraded the once dark skies, the telescope is still used today. Using adaptive optics, which removes the blurring effects of the atmosphere, the telescope can now see much finer detail. These modifications have extended the useful working life of this venerable telescope, so that it is still at the vanguard of astronomical research.