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Prism
Pair of 11 inch lens prisms forming part of declination and horizontal intensity magnetograph in a box. The second prism has been marked AST0720.1 and can be found via the Whole/Part toggle.
On manuscript: "162 Combination of cylindrical Lens and reflecting prism used in the original magnetograph from November 1880 onwards. The purpose was to bring the traces of Declination and Horizontal Intensity (which were projected from opposite sides of the recording drum and had previously differed in time-phase, therefore, by approximately 12 hours) into the same time-phase. Their exact inclination was controlled by micrometer-screw with a graduated head to read the setting W M Mitchell 1939 July 12"
On manuscript: "162 Combination of cylindrical Lens and reflecting prism used in the original magnetograph from November 1880 onwards. The purpose was to bring the traces of Declination and Horizontal Intensity (which were projected from opposite sides of the recording drum and had previously differed in time-phase, therefore, by approximately 12 hours) into the same time-phase. Their exact inclination was controlled by micrometer-screw with a graduated head to read the setting W M Mitchell 1939 July 12"
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Object Details
| ID: | AST0720 |
|---|---|
| Collection: | Astronomical and navigational instruments |
| Type: | Prism |
| Display location: | Not on display |
| Creator: | Unknown |
| Date made: | 1880 |
| Credit: | National Maritime Museum, Greenwich, London |
| Measurements: | Overall: 16 mm x 280 mm x 33 mm |
| Parts: | Prism |