cassegrainteleskooppi

A Cassegrain telescope is a type of reflecting telescope that uses a combination of a primary parabolic mirror and a secondary hyperbolic mirror to form an image. Light enters the telescope tube and strikes the primary mirror, which reflects it towards a focal point. Before reaching the primary focal point, the light is intercepted by a small, convex secondary mirror placed in front of the primary mirror. This secondary mirror reflects the light back down through a hole in the center of the primary mirror, where it is then focused by the primary mirror to form a final image at the eyepiece or detector.

This design offers several advantages. It is more compact than a Newtonian reflector of the same focal length because the light path is effectively folded. This makes the telescope tube shorter and more manageable. The Cassegrain design also provides a longer effective focal length compared to its physical tube length, which can be beneficial for achieving high magnification.

The primary mirror is typically parabolic, and the secondary mirror is hyperbolic. The precise curves and positioning of these mirrors are critical for achieving a sharp image. Cassegrain telescopes are widely used in both amateur and professional astronomy. Many large observatory telescopes, such as the Hubble Space Telescope, utilize variations of the Cassegrain design, often incorporating additional optical elements to correct for aberrations and improve image quality. Simpler versions, known as Newtonian reflectors, share the principle of using two mirrors but differ in the shape and placement of the secondary mirror and the location of the focuser.