Sextant john campbell
For example, the sextant shown alongside has a scale graduated from −10° to 142°, so that is basically a quintant: the frame is a sector of a circle subtending an angle of 76° (not 72°) at the pivot of the index arm.
The necessity for the doubled scale reading follows by consideration of the relations of the fixed ray (between the mirrors), the object ray (from the sighted object) and the direction of the normal perpendicular to the index mirror.
The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart—for example, sighting the Sun at noon or Polaris at night (in the Northern Hemisphere) to estimate latitude.This article is about the sextant as used for navigation.For the astronomer's sextant, see Sextant (astronomical).Full-size Vernier sextants were, in skilled hands, instruments of great accuracy, practicality and beauty - a joy to own and use, but also essential to the safety of the ship. £0.00 per line for up to 50 characters including space per line (max 6 lines).
Additional characters £0.00 each Express delivery will take an extra day for all personalised products.Our replica is dedicated to Royal Navy Captain John Campbell, who developed the instrument in 1757.