Cassegrain configuration

(kass -ĕ-grayn) One of the configurations in which a large reflecting telescope can be used. A small secondary mirror with a convex hyperboloid shape intercepts the beam of radiation before it reaches the prime focus of the primary mirror (see illustration). The secondary reflects the beam back down the tube, through a central hole in the primary mirror, to a focal point just behind it. This is the Cassegrain focus. It is more accessible than the prime focus and is incorporated into many reflecting telescopes, notably the Schmidt telescope and the Maksutov telescope.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Mentioned in

References in periodicals archive

A few years later, Italian optical designer Massimo Riccardi worked Honders's system into the Cassegrain configuration found in today's astrographs.

Officina Stellare's Veloce RH200 astrograph: this 8-inch f/3 catadioptric system hits a lot of sweet spots for today's astrophotographers

The cassegrain configuration for the X-band portion of the antenna is an adaptation of a 17th century optical telescope design.

Subreflector Developed for Simultaneous S and X-Band from a Single Antenna

For our night of observing it was set up in its "bent" Cassegrain configuration. Because the primary mirror isn't perforated, the only way to achieve a Cassegrain focus is to direct the light path out the side of the tube with a flat tertiary mirror.

An Amateur's Night on Mount Wilson

We have been unable to find any written records that address the condition of the reflecting surfaces of the three mirrors used in the Cassegrain configuration. (The 100-inch primary is not perforated.) If all three mirrors were not silvered, the resulting light loss would be about 3 1/2 magnitudes per unsilvered surface.

First-light doubts on Mount Wilson

This has led to a need for shorter feeds for use in Cassegrain configurations.

A compact monopulse feed for tracking antennas. (Product Feature)

Maksutovs in f/10 to f/16 Cassegrain configurations have been popular in the astronomy marketplace since Questar introduced its 311/42-inch model in the 1950s.

A Pair of High-Performance Maksutovs: Here's the optical lowdown on a pair of high-end Maksutov catadioptrics from Russia