Encke's Comet, 22 September 1848.
© Science Museum / Science & Society Picture Library
Encke's Comet as seen from the observatory at Hartwell Manor, Buckinghamshire. Encke's comet (discovered by J L Pons in 1818) was named after German astronomer Johann Franz Encke (1791–1865) who calculated its orbit, found the period of recurrence (3.3 years), and accurately predicted the date of its return. Illustration from 'aedes Hartwellianae, or notices of the manor and mansion of Hartwell' by William Henry Smyth (1788-1865), published in London in 1851.