Secondary Mirror

A secondary mirror (or secondary) is a second light gathering and focusing surface in a reflector telescope. Light gathered by the primary mirror is directed towards a focal point typically past the location of the secondary. The secondary directs the light either out a side opening of the tube (Newtonian reflector) or back towards a focal point behind and through the primary (Cassegrain reflector). The secondary is typically supended by X-shaped struts (sometimes called a "spider") in the path of light between the souce and the primary, however it is important to realize that this does not cause large distortions in the image. Every point on the primary individually forms an image, with additional area increasing the brightness of the final image, not changing the shape of the image. That said, secondaries and their supports can cause minor distortion to the point spread function, resulting in the cross-shaped "diffraction spikes" radiation from bright sources in many popular images. See also: telescope

 

<< PreviousWord BrowserNext >>
boom, antwerp
vaginal lubrication
us weapon production (1942 1945)
national diabetes information clearinghouse
huell howser
champion (supermarket)
the eleventh hour
mna
clinux
equality party (quebec)
list of fleets
quebec general election, 1998
quebec general election, 1994
table mountain pine
quebec general election, 1989
quebec general election, 1985
quebec general election, 1981
japanese red pine
frederick winston furneaux smith, 2nd earl of birkenhead
ismail enver
british pacific fleet
3 (telecommunications)
quebec general election, 1976
battle of washita river
pitch (baseball)
quebec general election, 1973
quebec general election, 1970
quebec general election, 1966
national myth
british eastern fleet
islamic accounting
oligomeric proanthocyanidin
james kreuser
opc
edouard jacques burgues de missiessy
richard hofstadter
list of subcamps of mauthausen
quebec general election, 1960
list of allied warships that served at gallipoli
naafi
moreton island
british grand fleet
international bridge
pyrenean shepherd