This octant, which probably dates from the late eighteenth century, has a mahogany frame and index arm. The boxwood scale is graduated every 20 minutes from 0 to 90 degrees and read by transversals to 2 minutes of arc. The top of the scale is numbered counterclockwise for zenith distances. There is also a back sight and a back horizon glass that can be used to measure angles greater than 90°.
Our collection database is a work in progress. We may update this record based on further research and review. Learn more about our approach to sharing our collection online.