On a closely connected peak half a mile to the east of the Observatory, and 50 feet higher, are the reservoirs from which water for household and photographic purposes is distributed.

Another peak seven-eighths of a mile to the east is the summit of Mount Hamilton; it is 180 feet higher than the Observatory, and supports the reservoirs supplying power for moving the dome, raising the movable floor, and winding the driving clock of the great telescope.

It is 18 metres (60 ft) in diameter, and can be raised or lowered through a distance of 16+1⁄2 feet (5.0 m), its purpose being to bring the observer within convenient reach of the eye end of the telescope.

He gave the contract for casting the high quality optical glass blanks, of a size never before attempted, to the firm of Charles Feil in Paris.

On the evening of January 3, the telescope saw first light,[2] and users found that the instrument could not be focused—an error in the estimation of the lens' focal length had caused the tube to be built too long.