Although acquired as a portrait of Nevil Maskelyne, fifth Astronomer Royal at Greenwich (1765 -1811), the late Derek Howse, former Head of Astronomy at NMM and Maskelyne's biographer, firmly believed that this received attribution was wrong, given the sitter's dissimilarity to Louis van der Puyl's Maskelyne portrait of 1785 owned by the Royal Society. The latter shows him in clerical dress against the background of the Royal Observatory but is itself rather untypical in suggesting sharper features than Maskeyne had, compared to other portraits more recently added to the NMM collection. These include an oil of 1804 by John Russell (ZBA5100) and a miniature of 1801 (ZBA5688), both also showing him in black clerical dress, as one would expect in formal images. These and the Museum's undated head study in pastel by Russell (ZBA4305) confirm the matter by clearly showing Maskelyne had blue eyes while the sitter's here are hazel. This otherwise fine portrait, against a suitably learned or senatorial classical column, is therefore probably another non-clerical astronomer or theoretician, so far unidentified. He has some resemblance to George Parker, 2nd Earl of Macclesfield (1697-1764) who was an eminent amateur astronomer and President of the Royal Society from 1752 to his death, and was also painted by Hogarth. However, this is also doubtful given that Macclesfield died in 1764 and the painting is signed and dated 'Jno Downman Pinx 1779'. The book and fold-out planetary plate that he holds - apparently of Saturn and Jupiter - are an obvious clue to his specific interests but have not yet been identified. The van der Puyl portrait of Maskeyne is reproduced in colour in Howse, 'Greenwich Time and the Longitude', (2nd ed., NMM/Philip Wilson 1996).