A superb early 19th Century antique navigator’s Octant engraved THOMPSON, YARMOUTH. - The early features found on this Octant probably date it from 1810 to 1820. - Simon Thompson is recorded as working from two addresses in Yarmouth from 1805 to 1844.

The Octant’s ‘T’ shaped frame is constructed from ebony with brass fittings and ivory scales. The arc scale is finely engraved and crisp, reading from -2 degrees to 99 degrees. It is further divided into 20 minutes of arc and can measure angles of up to 90 degrees. The arc scale is also engraved with the fouled anchor mark, this was a trade mark for scales divided by JESSE RAMSDEN who was recognised by the Board of Longitude for the accuracy of his scales.

The ivory makers plaque is situated on the crossbar of the octant frame and is engraved THOMPSON, YARMOUTH.

This Octant has the early flat and unbraced brass index arm, which is fitted with an ivory Vernier scale engraved from 0 to 20 and reading 1 minute of arc. There is a clamping screw to the reverse side and there is also a pivoting brass index arm back stop fitted to the frame.