Joseph Crabtree observatory magnifier
- Author: Anonymous
- Publication date: late nineteenth century
- Physical description: Brass with glass dome.
- Dimensions: (diameter) 22cm (8.5 inches).
- Inventory reference: 12771
The observatory magnifier is believed to have been designed in 1804 by the legendary British inventor and polymath Joseph Crabtree (1754–1854). It was intended to aid the reading of nautical charts aboard ship, and is still in use today. The present example is particularly large measuring 22 centimetres in diameter.