[7] Decommissioned instruments include the Palomar Testbed Interferometer and the first telescopes at the observatory, an 18-inch (46 cm) Schmidt camera from 1936.

Astronomer George Ellery Hale, whose vision created Palomar Observatory, built the world's largest telescope four times in succession.

[8] He published a 1928 article proposing what was to become the 200-inch Palomar reflector; it was an invitation to the American public to learn about how large telescopes could help answer questions relating to the fundamental nature of the universe.

A larger telescope would not only furnish the necessary gain in light space-penetration and photographic resolving power, but permit the application of ideas and devices derived chiefly from the recent fundamental advances in physics and chemistry."

It was built by Caltech with a $6 million grant from the Rockefeller Foundation, using a Pyrex blank manufactured by Corning Glass Works under the direction of George McCauley.

Astronomers using the Hale Telescope have discovered quasars (a subset of what was to become known as Active Galactic Nuclei) at cosmological distances.

Porter was also responsible for much of the technical design of the Hale Telescope and Schmidt Cameras, producing a series of cross-section engineering drawings.

The Hale Telescope[3] remains in active research use and operates with a diverse instrument suite of optical and near-infrared spectrometers and imaging cameras at multiple foci.

The survey covered the sky from a declination of +90° (celestial north pole) to −27° and all right ascensions and had a sensitivity to +22 magnitudes (about 1 million times fainter than the limit of human vision).

The Digitized Sky Survey (DSS) produced images which were based on the photographic data developed in the course of POSS-I.

The camera for the Palomar QUEST Survey was a mosaic of 112 charge-coupled devices (CCDs) covering the whole (4° × 4°) field of view of the Schmidt telescope.

Current research programs on the 200-inch Hale Telescope cover the range of the observable universe, including studies on near-Earth asteroids, outer Solar System planets, Kuiper Belt objects, star formation, exoplanets,[29] black holes and x-ray binaries, supernovae and other transient source followup, and quasars/Active Galactic Nuclei.

[5] The 60-inch telescope operates robotically, and supports ZTF by providing rapid, low-dispersion optical spectra for initial transient classification using the for-purpose Spectral Energy Distribution Machine (SEDM)[31] integral field spectrograph.

[35] Similarly the observatory actively maintains an extensive website[36] and YouTube channel[37] to support public engagement.