An Etymological Dictionary of Astronomy and Astrophysics

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فرهنگ ریشه‌شناختی اخترشناسی-اخترفیزیک

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Herschelian telescope
  تلسکوپ ِ هرشل، دوربین ~  
teleskop-e Herschel, durbin-e ~
Fr.: télescope de Herschel  

A → reflecting telescope in which the → primary mirror is tilted so that light is focused near one side of the open end of the tube. The → eyepiece then picks up this light directly, avoiding light loss from reflection by a → secondary mirror. The drawback is → astigmatism, unless the → focal ratio is large. Herschel used this design in his giant 48-inch instrument.

See also: → Herschel; → telescope.