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sextant click to hear : sextant

Optical instrument for measuring the angle between a heavenly body and the horizon to determine the ship’s position.
sextant image
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See sextant in : french | spanish
drum horizon shade micrometer screw vernier scale graduated arc frame horizon mirror index shade telescope lens hood index arm index mirror index

drum click to hear : drum

Thumbnail for turning the micrometer screw.

horizon shade click to hear : horizon shade

Colored glass that blocks certain rays in the light spectrum to filter out ambient light.

micrometer screw click to hear : micrometer screw

Screw with a head graduated in minutes that is turned to set the index arm precisely.

vernier scale click to hear : vernier scale

Small graduated rule that slides along the ruler and is used to read very precise measurements.

graduated arc click to hear : graduated arc

Arc graduated in degrees; the observed angle measurement is read from it.

frame click to hear : frame

Support for the various components of the sextant.

horizon mirror click to hear : horizon mirror

Fixed mirror in front of the telescope; it is aimed at the horizon and the image of the Sun is projected on it.

index shade click to hear : index shade

Colored glass that blocks certain rays in the light spectrum to filter out ambient light.

telescope click to hear : telescope

Optical instrument that magnifies an observed object.

lens hood click to hear : lens hood

Device attached to the telescope’s eyepiece that shields the eye from light coming from the source and from strong ambient light.

index arm click to hear : index arm

Moving arm on the sextant that measures the displacement angle on the graduated arc to determine the height of the observed heavenly body.

index mirror click to hear : index mirror

Mirror integrated with the index arm that is positioned so that the Sun reflects on the horizon mirror.

index click to hear : index

Guide mark that helps to read the graduation marks on the arc.