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Gregorian primary mirror
A 3-inch (76.2mm) primary Gregorian mirror made of speculum metal, focal length 1.5ft.
A Gregorian telescope typically has two mirrors - a large circular concave mirror with a hole in the middle called a primary mirror, this mirror is used to collect light from the distant object being viewed, and a small circular concave mirror known as a secondary mirror, for reflecting the light collected into the eyepiece. The hole in the middle of the primary mirror is there so the light can get from the secondary mirror to the eyepiece through the primary mirror. William Herschel made and used Gregorian telescopes before moving on to Newtonian and later Herschelian (to his own design) telescopes.
This mirror was found in a tin case, in a partitioned wooden box, with the 20ft telescope in the loft of the Herschel's family home in Slough.
A Gregorian telescope typically has two mirrors - a large circular concave mirror with a hole in the middle called a primary mirror, this mirror is used to collect light from the distant object being viewed, and a small circular concave mirror known as a secondary mirror, for reflecting the light collected into the eyepiece. The hole in the middle of the primary mirror is there so the light can get from the secondary mirror to the eyepiece through the primary mirror. William Herschel made and used Gregorian telescopes before moving on to Newtonian and later Herschelian (to his own design) telescopes.
This mirror was found in a tin case, in a partitioned wooden box, with the 20ft telescope in the loft of the Herschel's family home in Slough.
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Object Details
| ID: | AST0807 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Gregorian primary mirror |
| Display location: | Not on display |
| Creator: | Herschel, William |
| Date made: | Unknown |
| People: | Herschel, William |
| Credit: | National Maritime Museum, Greenwich, London, Herschel Collection |
| Measurements: | Overall: 8 mm; Diameter: 73 mm |