|Place of work||Greenwich|
||March or May 1765 – Nov 1766
Born in Brierly, Yorkshire, Joseph Dymond was the first assistant to be appointed by the fifth Astronomer Royal, Nevil Maskelyne. Although Bliss died on 2 September 1764, Maskelyne was not appointed as his successor until 8 February 1765. Meanwhile, (according to Abram Robertson who wrote the preface to the second volume of Bradley’s Observations), Charles Green (who had served under both Bradley and Bliss), continued as Assistant, apparently making his last observation on 15 March 1765, the day before Maskelyne took up residence. Howse (Nevil Maskelyne, Cambridge, 1989), goes on to say that Green left on Lady Day, 25 March, 1765.
One record left by Maskelyne (RGO4/28) indicates that Dymond started at the Observatory on 25 March. Another supposedly gives the date as 7 May, which is the date of Maskelyne’s first published observation with the transit telescope. There is also an inconsistency over the dates on which Dymond is supposed to have left, with one record said to state 11 November 1766, whilst (RGO4/28) states 14 November. The reason why either Green or Dymond left the Observatory when they did is not known.
Amongst Dymond’s duties was assisting Maskelyne with the testing of Harrison’s watch H4 for the Board of Longitude. In the published observations, those made by Dymond are signified with a D. (Maskelyne appears to have continued this practice with later assistants until the end of 1769).
The Royal Society organised two expeditions to observe the Transit of Venus on 3 June 1769 – one lead by Cook with Green as his astronomer, the other by William Wales (brother-in-law of Charles Green and one of the first Computers recruited by Maskelyne to work on the Nautical Almanac) with Dymond as his assistant. Whilst Cook was sent to Tahiti, Wales and Dymond were sent to Hudson’s Bay in Canada. Because of the pack ice present in Hudson Bay for most of the year, Wales and Dymond had to leave the previous year, departing at the end of May and arriving at their destination, Churchill, on 10 August 1768. The weather on the day of the Transit was less than perfect, but sufficient for the necessary observations to be made. The two observers however differed by 11 seconds in their measurements of the initial contact, causing Wales much distress. Arriving back in England at the end of the year, their results were eventually published in 1770. Whilst Wales continued to have a successful career, little is know of Dymond after the Hudson’s Bay voyage. According to Lalande in his Bibliographie Astronomique p.538, Dymond retired to Nottinghamshire.