A History of the Navigator's Sextant
This pre-history of the sextant, as we might call it, will emphasize the problems that were to be overcome in leading up to the invention, or rather evolution, of an instrument that has for long been the very symbol of the navigator's art.
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The Genesis of the Mariners Anglemeasuring
The Seamans Quadrant
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adjusted Alhidada alidade artificial horizon astronomical astronomical navigation axis backstaff backward observation beam compass brass celestial centre century chord circle coincidence cross-piece cross-staff Davis quadrant degrees described designed device diameter divided division edge Edmond Halley error eye-end field of view fitted frame graduated arc Hadley quadrant Hadley's half-transom Harriot heavenly body Hipparchus hole horizon glass horizon mirror horizon vane illustrated in figure inches index arm index bar index mirror instrument-maker invented Jesse Ramsden John Hadley latitude Lecky length limb London longitude mariner's astrolabe measuring altitudes measuring angles mercury meridian metal method minute of arc minutes Nautical Astronomy object observed body octant parallel pinnules planispheric planispheric astrolabe plate Portuguese position prism radius Referring to figure reflecting instrument Royal Society seaman's quadrant seamen sextant shadow vane ship speculum staff star Sun's altitude surface surveying tangent screw telescope transom tube upper vernier scale vide Wollaston prism