Newtonian secondary mirror

An elliptical plane mirror made as a secondary mirror for a Newtonian reflector telescope. The diameter of the minor axis of this mirror is 1.15inches (29.21mm).

In a Newtonian reflector telescope the eyepiece is at the side of the tube. Light comes in at one end, is reflected off the objective (or primary) mirror and onto this mirror which directs the light towards the eyepiece. William Herschel, with help from his brother Alexander and his sister Caroline made a number of these mirrors to go in the telescopes they made to use and to sell.

Object Details

ID: AST0823
Collection: Astronomical and navigational instruments
Type: Newtonian secondary mirror
Display location: Not on display
Creator: Herschel, Caroline Lucretia; Herschel, William Johann Alexander Herschel
Date made: circa 1800
Credit: National Maritime Museum, Greenwich, London, Herschel Collection
Measurements: Overall: 29.21 mm