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7ft
Unfinished 6-inch Newtonian primary mirror of speculum metal. When finished this mirror would probably be made to have a focal length of around 7ft. The actual diameter of this mirror is 165.1mm. One surface has been roughly smoothed, in preparation for grinding.
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. A mirror of this size and focal length would have been used in one of their 7ft telescopes.
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. A mirror of this size and focal length would have been used in one of their 7ft telescopes.
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Object Details
| ID: | AST0863 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Unfinished Newtonian primary mirror |
| Display location: | Not on display |
| Creator: | Herschel, William |
| Date made: | 1773-1822 |
| Credit: | National Maritime Museum, Greenwich, London, Herschel Collection |
| Measurements: | Overall: 18 mm; Diameter: 167 mm |