Achromatic telescope. Long brass telescope with smaller viewfinder telescope on a tall mahogany stand with three legs.

ABDNP:200006a

'Dollond's achromatic telescope of two and three quarter inch aperture and 4 feet focus, with polar axis, on a mahogany stand, 2 astronomical and 1 terrestrial eyepiece and a divided object glass micrometer.' The instrument in the University's possession fits this description except that it has only one eyepiece. It is signed 'Dollond, London' but unnumbered. Mackay records (in 'The Theory and Practice of finding Longitude at Sea or Land' pg 199, first edition, London 1793) that for observations of Jupiter's satellites he used powers of 'about 80 and 115 according to the state of the atmosphere.' In the observatory notebook (A.U.L. Ms 504) he records powers of about 70 and 126 and always refers to the telescope as the '46 inch achromatic of Dollond.' Maskelyne suggested (in a letter to Patrick Copland, dated 7th Dec. 1780 in A.U.L. Ms 2886) that Sisson should make the mount but there is no record of whether he did or not. The cost was pounds £73.10. A similar telescope was purchased by the Radcliffe Observatory in 1774 and is illustrated as item 183 in R.T.Gunther 'Early Science in Oxford' vol.II opposite pg 314 (Oxford,1923). Dollond's divided object glass is shown in a photograph in the Van Marum collection catalogue (66) pg 298, fig 224 and also in R.T.Gunther ibid. opposite pg 329.

On equatorial mount with remains of sighting telescope . Its focal length and aperture are correct, as in the mount type and material. With object glass micrometer (separate) and one steadying arm (separate).

1781-1783

Brass, wood, glass

Dollond and Co., London

Patrick Copland, astronomy, science, history of science

Physical Object

81517c81-212a-40d1-933f-4ce83cd0e2d2