Pencil drawing of the 'great sunspot of March 29th 1837', with a scale of minutes and seconds, and various recorded measurements.

In March 1837 John would have been in South Africa with his family, working on his project to catalogue the nebulae, star clusters and double stars visible through his 20ft telescope for southern hemisphere.

A sunspot is a cool area on the Sun's surface which appears a dark dot when the Sun is observed through appropriate filters. These areas have higher magnetic activity as well as lower temperatures than the surrounding areas. Sunspot activity has a cycle of around 11 years, with a large number of sunspots visible at the height of its activity and none at its minimum. It is during its height that the Northern Lights (aurora borealis) are most likely to be seen.

The drawing is on a thin, rectangular piece of paper irregular along one long edge and torn along the opposite edge. The paper is contained in brown envelope.