Marine Sextant
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Marine SextantHusun (H. Hughes & Son)

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This 20th c. marine sextant was produced in London and evolved from the earlier octant, with an arc extended to 120°. Its paired mirrors align a celestial body with the sea horizon, so the navigator can read the angle directly from the instrument. Combined with an accurate time reference, such sights support reliable latitude fixes, and the same optics can also measure horizontal angles between landmarks.