Cassegrain Reflector

A type of reflecting telescope where the main mirror has a central hole. Light from an object is reflected off the primary mirror up to the secondary mirror and back through the hole in the primary to be focused in the eyepiece tube. The primary mirror is a spherical mirror and is therefore easier and cheaper to make than a parabolic (slightly elliptical) mirror. Correction for spherical aberration is made by having a parabolic secondary mirror. The path of the light is also folded on itself which makes its tube much shorter, lighter and more portable than a refracting or a Newtonian reflector of the equivalent aperture. Popularised by Meade and Celestron telescope manufacturing companies in a modified form.

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