With funding from the Rockefeller Foundation in 1928, he orchestrated the planning, design, and construction of the observatory, but with the project ending up taking 20 years he did not live to see its commissioning.

These telescopes were very successful, leading to the rapid advance in understanding of the scale of the Universe through the 1920s, and demonstrating to visionaries like Hale the need for even larger collectors.

Compared to the usual parabolic primary, this design would have provided sharper images over a larger usable field of view.

Construction of the observatory facilities and dome started in 1936, but because of interruptions caused by World War II, the telescope was not completed until 1948 when it was dedicated.

It has also used lucky cam imaging, which in combination with adaptive optics pushed the mirror close to its theoretical resolution for certain types of viewing.

[19] In the optical shop in Pasadena (now the Synchrotron building at Caltech) standard telescope mirror making techniques were used to turn the flat blank into a precise concave parabolic shape, although they had to be executed on a grand scale.

A mirror beyond that size would also sag slightly under its own weight as the telescope is rotated to different positions,[24][25] changing the precision shape of the surface, which must be accurate to within 2 millionths of an inch (50 nm).

[31] Halley's Comet (1P) upcoming 1986 approach to the Sun was first detected by astronomers David C. Jewitt and G. Edward Danielson on 16 October 1982 using the 200-inch Hale Telescope equipped with a CCD camera.

[33] One was Caliban (S/1997 U 1), which was discovered on 6 September 1997 by Brett J. Gladman, Philip D. Nicholson, Joseph A. Burns, and John J. Kavelaars using the 200-inch Hale Telescope.

[38] In October 2017 the Hale Telescope was able to record the spectrum of the first recognized interstellar object, 1I/2017 U1 ("ʻOumuamua"); while no specific mineral was identified it showed the visitor had a reddish surface color.

[39][40] In December 2023 the Hale Telescope began serving as the receiving antenna for the Deep Space Optical Communications experiment on NASA's Psyche mission.

Specifically, it is easier to obtain images when the planet is especially large (considerably larger than Jupiter), widely separated from its parent star, and hot so that it emits intense infrared radiation.

However, in 2010 a team from NASA's Jet Propulsion Laboratory demonstrated that a vortex coronagraph could enable small scopes to directly image planets.