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°.

Date Made: late 18th century

Location: Currently not on view

See more items in: Medicine and Science: Physical Sciences, Navigation, Measuring & Mapping


Exhibition Location:

Data Source: National Museum of American History

Id Number: PH.314493Catalog Number: 314493Accession Number: 204107

Object Name: octant

Measurements: overall: 7.6 cm x 37.8 cm x 46 cm; 3 in x 14 7/8 in x 18 1/8 inoverall: 3 in x 14 7/8 in x 18 1/4 in; 7.62 cm x 37.7825 cm x 46.355 cm

Guid: http://n2t.net/ark:/65665/ng49ca746aa-47dc-704b-e053-15f76fa0b4fa

Record Id: nmah_1187745

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.

If you would like to know how you can use content on this page, see the Smithsonian's Terms of Use. If you need to request an image for publication or other use, please visit Rights and Reproductions.