* 1672-Laurent Cassegrain designs the Cassegrain telescope

In more complex designs, such as the Cassegrain and Gregorian, a secondary reflector is used to direct the energy into the parabolic reflector from a feed antenna located away from the primary focal point.

Offset feed is also used in multiple reflector designs such as the Cassegrain and Gregorian, below.

The designs of some specific types of parabolic antenna, such as the Cassegrain and Gregorian, come from similarly named analogous types of reflecting telescope, which were invented by astronomers during the 15th century.

* Aperture blockage-In front-fed parabolic dishes where the feed antenna is located in front of the dish in the beam path ( and in Cassegrain and Gregorian designs as well ), the feed structure and its supports block some of the beam.

They are also used to re-direct and extend the light path and modify the final image in designs such as Cassegrain reflectors.

The multilayer technology allows conventional telescope forms ( such as the Cassegrain or Ritchey-Chretien designs ) to be used in a novel part of the spectrum.

* Schmidt – Cassegrain telescopes are one of the most popular commercial designs on the amateur astronomical market, having been mass-produced since the 1960s.

This led to professional and amateur designers almost immediately experimenting with variations, including Newtonian, Cassegrain, and wide-field camera designs.

There are many Maksutov designs that use a Cassegrain configuration, mounting a convex secondary mirror near the focus of the primary mirror.

In the 1980s Dave Shafer and Ralph W. Field came out with sub-aperture Cassegrain designs based on this idea.

The 8 inch model employs a refractor style rack and pinion focuser while in the larger designs the primary mirror is moved as in most other small to medium sized Cassegrain designs.

This particular design is also unusual in that it is a Cassegrain design but has a fixed primary and refractor style rack and pinion focuser which removes the image shift issues seen with other catadioptric designs.

To avoid blockage from the sub-reflector asymmetric designs such as the open Cassegrain can be employed.

Schmidt – Newtonians also costs less than the more commonly produced Schmidt – Cassegrains since they don't have the added curved secondary mirror or the complicated primary mirror focusing mechanism found in most Schmidt – Cassegrain designs.

However in offset Cassegrain configurations, the primary dish reflector is asymmetric, and its focus, and the secondary reflector, are located to one side of the dish, so that the secondary reflector does not partially obstruct the beam.

The radii of curvature of the primary and secondary mirrors, respectively, in a two-mirror Cassegrain configuration are

They are often used with secondary reflector antennas such as the Cassegrain.

By convention these features are identified on lunar maps by placing the letter on the side of the crater midpoint that is closest to Cassegrain.

* Maksutov – Cassegrain telescopes are the most commonly seen design that uses a meniscus corrector, a variant of the Maksutov telescope.

Most Maksutovs manufactured today are this type of ' Cassegrain ' design ( called either a " Gregory – Maksutov " or " Spot-Maksutov ") that use all-spherical surfaces and have, as secondary, a small aluminized spot on the inner face of the corrector.

Sub-aperture corrector Maksutovs are currently manufactured by Vixen telescopes, their VMC ( Vixen Maksutov Cassegrain ) models.

One very well-corrected design example would be the concentric ( or monocentric ) Schmidt – Cassegrain, where all the mirror surfaces and the focal surface are concentric to a single point: the center of curvature of the primary.

There are three types of telescopes, all Cassegrain reflector antennas with parabolic primary mirrors and hyperbolic secondary mirrors:

In a symmetrical Cassegrain both mirrors are aligned about the optical axis, and the primary mirror usually contains a hole in the centre thus permitting the light to reach an eyepiece, a camera, or a light detector.

In the Argunov – Cassegrain telescope all optics are spherical, and the classical Cassegrain secondary mirror is replaced by a sub-aperture corrector consisting of three air spaced lens elements.

Four different instruments are available to be mounted at the Cassegrain focus.

* The Boyden-UFS Telescope, which is also known as the Rockefeller Reflector, is a Cassegrain reflector.

There is also a secondary focal station, the f / 15 Cassegrain focus, which possesses a 20 arcminute field of view and is the mount point for the IDS.

The Rutten Maksutov – Cassegrain ( also called a Rumak or Sigler Maksutov ) has a separate secondary mirror mounted on back of the meniscus corrector, sometimes similar to the corrector / mirror holder configurations found in commercial Schmidt – Cassegrains.

The Cassegrain design is also used in catadioptric systems.

An unusual variant of the Cassegrain is the Schiefspiegler telescope (" skewed " or " oblique reflector ", also known as " kutter telescope " after its inventor Anton Kutter ) which uses tilted mirrors to avoid the secondary mirror casting a shadow on the primary.

Later satellites had larger mirrors, with a diameter of around 2. 9 – 3. 1 m. Jane's Defence Weekly indicates that the secondary mirror in the Cassegrain reflecting telescope system could be moved, allowing images to be taken from angles unusual for a satellite.

In telecommunications and radar, a Cassegrain antenna is a parabolic antenna in which the feed radiator is mounted at or behind the surface of the concave main parabolic reflector dish and is aimed at a smaller convex secondary reflector suspended in front of the primary reflector.

* Another reason for using the Cassegrain design is to increase the focal length of the antenna, to improve the field of view Parabolic reflectors used in dish antennas have a large curvature and short focal length, to locate the focal point near the mouth of the dish, to reduce the length of the supports required to hold the feed structure or secondary reflector.

The convex secondary reflector of the Cassegrain increases the focal length, and thus the field of view, so these antennas usually use a Cassegrain design.

The elements were equatorially mounted 13-m Cassegrain antennas, on an ( almost ) east-west baseline.

The Cassegrain reflector is a combination of a primary concave mirror and a secondary convex mirror, often used in optical telescopes and radio antennas.

A beam waveguide antenna is a type of complicated Cassegrain antenna with a long radio wave path to allow the feed electronics to be located at ground level.

Just north of Copley is Keeble Observatory, which includes a 12 " Cassegrain reflector optical telescope and two radio telescopes.

A Cassegrain radio antenna – the 70 meter dish at Jet Propulsion Laboratory | JPL's Goldstone Deep Space Communications Complex | Goldstone antenna complex.