Sextant - Brass

A reproduction Stanley pocket sextant (essentially a circular vernier sextant) that measures angles between two objects—usually the sun or star and the horizon—using mirrors and a graduated arc. The sextant is unscrewed and the base joins to the instrument. The circular brass body holds a small sextant mechanism: a fixed mirror, a moving index mirror carried on the pivoted arm, and a silvered arc with degree graduations around the edge. The knurled micrometer drum and smaller clamp screw let you move the index arm extremely precisely along the arc, then lock it when you have the reading, you sight through the central peephole; one half of the view is direct, the other half is seen by reflection in the mirrors, just like a full‑size marine sextant. To measure an altitude, you hold the open instrument to your eye and point it so you see the horizon (or other reference) through the sight you then rotate the index arm with the micrometer until the reflected image of the sun/star drops down to just “kiss” the horizon in the sight when the two images coincide, you read the angle from the degree scale and micrometer, then apply the usual corrections (index error, dip, refraction, etc.) as with a standard sextant to obtain an accurate altitude or horizontal angle.

The sextant measures 7.5cm in diameter and is untested, it is a nice solid item.