- Flamsteed , John . 1982 . The ‘Preface’ to John Flamsteed's ‘Historia Coelestis Britannica’, 1725 Edited by: Chapman , A. 113 – 126 . London based on a translation by D. Johnson, National Maritime Museum Monograph No. 52
- Smith , Robert . 1738 . A Compleat System of Opticks 350 – 350 . Cambridge para. 885.
- For a full account of this instrument's early history and use at Greenwich, see Howse H.D. Greenwich Observatory III: The Buildings and Instruments London 1975 79 81 It was also described in Abraham Rees, The Cyclopaedia: Or, Universal Dictionary of Arts, Sciences, and Literature, 45 vols (London, 1819–20), plates vol. I (1820), section ‘Astronomical Instruments’, plate XIII.
- Bradley , James . 1832 . Miscellaneous Works and Correspondence Edited by: Rigaud , S.P. 56 – 56 . Oxford
- Maskelyne , Nevil . 1776 . Astronomical Observations Vol. I , xii – xii . London The necessary alignment of the polar axis could be accomplished by ‘a small common quadrant’ claimed Smith (footnote 3), 353, para. 891.
- Maskelyne . 1975 . Greenwich Observatory III: The Buildings and Instruments Edited by: Howse . 81 – 81 . London cited by
- Hind , John Russell . 1852 . The Comets: A Descriptive Treatise upon these Bodies 149 – 149 . London
- Yeomans , Donald K. 1991 . Comets, A Chronological History of Observation, Science, and Folklore 157 – 158 . New York I am also grateful to Dr David Hughes of Sheffield University for his comments on the ‘fashionable’ status of comets in astronomy in the wake of the return of Halley in 1758–9: private correspondence, July 1994.
- Bird to Hornsby, Royal Astronomical Society 1771 January 29 [hereafter RAS] Radcliffe MS, Hornsby A1.13.
- Bird to Hornsby, RAS Radcliffe MS 1771 February 3 Hornsby A1.15.
- The Sector had clearly been desired by Hornsby right from the start. An undated memorandum speaks of ‘one Equatorial Sector of 5 feet with achromatic Object Glasses & Circles of 3 feet diameter’, RAS Radcliffe MS Hornsby A1.8.
- Articles of Agreement, Bird and Radcliffe agents, March 1771 2 MHS Radcliffe MS 29.
- Maskelyne to Hornsby RAS Radcliffe MS 1771 June 13 Hornsby A1.60 (1–3). As early as 29 January 1771, however, Bird had clearly formulated some plans when he suggested to Hornsby ‘An Equatorial Sector with 5ft. Dollond's Tel. and Circles of 3ft. such as the Astro. Roy. is now about [£]200·00’ (footnote 10).
- Bird to Hornsby, RAS Radcliffe MS 1772 May 5 Hornsby A1.18.
- Howse . 1975 . Greenwich Observatory III: The Buildings and Instruments 81 – 82 . London
- Bennett , J.A. 1993 . “ Equipping the Radcliffe Observatory: Thomas Hornsby and his Instrument-Makers ” . In Making Instruments Count. Essays on Historical Scientific Instruments presented to Gerard L'Estrange Turner , Edited by: Anderson , R.G.W. , Bennett , J.A. and Ryan , W.F. 232 – 241 . Aldershot : Variorum . (234)
- Hornsby first purchased a 43-inch transit from Bird in 1760, and a 32-inch quadrant in 1767. Both were his private property; Gunther R.T. Early Science in Oxford Oxford 1923 II 318 318 Also Bennett (footnote 17), 233.
- ‘Manuscript Book formerly belonging to the Duke of Marlborough’, MHS Radcliffe 16 (prepared by Thomas Hornsby for the Duke). See Equatoreal at Oxford 122 123 Undated but placed between transcribed astronomical letters of December 1785 and August 1786.
- Smith . 1738 . A Compleat System of Opticks 350 – 351 . Cambridge para. 886
- Vince , Samuel . 1790 . A Treatise on Practical Astronomy 147 – 147 . Cambridge
- Howse . 1975 . Greenwich Observatory III: The Buildings and Instruments 82 – 82 . London Vince (footnote 21), prefatory note.
- Howse . 1975 . Greenwich Observatory III: The Buildings and Instruments 82 – 82 . London
- Pearson , William . 1829 . An Introduction to Practical Astronomy Vol. II , 524 – 524 . London Howse (footnote 4) reproduces the observations of the 1815 comet from John Pond's Astronomical Observations (London, 1815), 242 as his Figure 76. Howse mentions the cannibalization on p. 82.
- Kongelige Bibliotek Copenhagen MS Ny. kgl. Saml. 377e. Thomas Bugge's travel diary, August-December 1777. Unpublished English translation (copy in MHS), 66 left.
- Note by S. P. Rigaud, 9 September 1830, RAS Radcliffe MS G.1, and cited in Guest Ivor Doctor John Radcliffe and his Trust London 1991 258 258 Quoted without source by Gunther (footnote 18), 336. Rees (footnote 4), XIII, (1819), article ‘Equatorial Instrument’ by William Pearson. Pearson says that it was better than Sisson's Greenwich Sector (which he had just described from Vince) and ‘was begun by Mr. Bird in the last year of his life, or the year preceding, for the Observatory at Oxford, and was finished by Mr. Troughton (the senior) about the year 1773 by order of Mr. Bird's executors’. Unpaginated, sig. 3H3 verso.
- MHS Radcliffe MS 46(2) This drawing of c. 1775–7 is on a loose sheet inserted into a volume of Abraham Robertson's papers in the Radcliffe collection.
- Draft of an unsigned letter by Thomas Hornsby, c. 1773, quoted in full by Gunther Early Science in Oxford Oxford 1923 II 336 336 No location is given for the original.
- Estimates for Radcliffe Buildings, 1772 [no further date or authorship], RAS Radcliffe MS A1.31. The Equatorial House was also referred to by John Hudson (Clerk to James Pears, the Oxford builder who finished the decorative work on the Observatory Tower in 1794) in a letter of 7 February 1834: ‘The Circular Building for the Equatorial was built by Mr. Keene—therefore between the years 1774 & 1776’ (when Keene was replaced by James Wyatt as Radcliffe Observatory architect): MHS Radcliffe MS 67.
- Hind . 1852 . The Comets: A Descriptive Treatise upon these Bodies 151 – 154 . London
- Published in The Herschel Chronicle Lubbock Lady Constance Cambridge 1933 79 79
- Published in The Herschel Chronicle Lubbock Lady Constance Cambridge 1933 80 80 J. B. Sidgwick, William Herschel, Explorer of the Heavens (London, 1953), 73ff. When discussing the search for Uranus, Sidgwick consistently refers to Hornsey at Oxford!
- Hornsby to Duke of Marlborough September 1781 25 RAS Radcliffe MS A2.12(2).
- Hornsby to Duke of Marlborough September 1781 26 RAS Radcliffe MS A2.13(1). At 04:30 hours on 25 September 1781, Uranus would have been high in the south-eastern sky before dawn, and would have crossed the meridian around 06:03 hours. I am indebted to Mr Ken Sheldon for having undertaken this calculation for me.
- MHS Radcliffe MS 16 Equatoreal at Oxford 122 122
- Hornsby to Duke of Marlborough, November 1781 29 RAS Radcliffe MS A2.20(1).
- Lubbock . 1933 . The Herschel Chronicle Edited by: Lubbock , Lady Constance . 106 – 107 . Cambridge discusses Hornsby's caution about herschel's ‘Comet’, and prints Hornsby's letter to William Herschel of 26 February 1782 on the matter. By 29 December 1781, he was acknowledging it as ‘The New Star’ in the Zenith Distances Observing Ledger (RAS Radcliffe MS 2.2), and by 30 December 1783 (RAS Radcliffe MS 2.3) as ‘Georgium Sidus’ though he had acknowledged its status as a planet before this date.
- The undated list of Radcliffe Observatory instruments itemizing ‘1 Equatorial Sector’ is in Abraham Robertson's papers, RAS Radcliffe MS B66. A similar reference to ‘1 Equatorial Sector’ exists as item 16 on an undated list among Robertson's papers in MHS Radcliffe MS 53. Also ‘Inventory of Astronomical Instruments & C. & C. in the Observatory at Oxford belonging to the Rt. Honble. & Honble. the Radcliffe Trustees’, MHS Radcliffe MS 53, 6. There is no contemporary date in ink on the document although ‘1827’ has been added in pencil. If 1827 is indeed the correct date, it would have been drawn up by Rigaud. See Rigaud (footnote 26). By 1863 the Equatorial Sector had sunk so far from general awareness in the Observatory that in the published Results of that year it was not even included with the Quadrants and Zenith Sector as part of the preserved ‘ancient instruments’: Results of Astronomical Observations made at the Radcliffe Observatory, Oxford, in the year 1863 Oxford ii undated)
- Gunther . 1923 . Early Science in Oxford Vol. II , 311 – 311 . Oxford
- MHS Radcliffe MS 46(2)
- Barrett , H.G.S. and Balk , J.G. 1934 . June MS drawing of Equatorial Sector and accompanying notes dated 13 in MHS MS Gunther 27 (5).
- The Sisson Sector for Greenwich, however, was not designed to read Declinations, but had a ‘Circle graduated to show North Polar Distances’, with 90° at the poles: Vince A Treatise on Practical Astronomy Cambridge 1790 142 142 I wish to thank H. D. Howse for his advice regarding the Declination/NPD reading properties of the Greenwich Sector by Sisson (private correspondence, June 1994).
- MHS Radcliffe MS 16 Equatoreal at Oxford 122 122
- Vince . 1790 . A Treatise on Practical Astronomy Cambridge does not specifically mention the presence of counter-weights in the post-1780 rebuild of the ‘eastern’ Sisson Sector at Greenwich, although a counter-balancing structure appears on the engraving of the instrument. It is not clear whether counterpoises would have been present in the original design of 1773: p. 142, and pl. 48.
- Although the circles of the Sisson Sectors for Greenwich do not seem to have survived in their original form, they also supported a pair of vernier-carrying alidades set at right angles to the central axis of the Sector ‘wedge’. One of these 5-ft Sector wedges, the only part of the original Sisson instruments to survive, is in the National Maritime Museum, Greenwich, collection and is illustrated in Howse Greenwich Observatory III: The Buildings and Instruments London 1975 79 81 Figure 77.
- MHS Radcliffe MS 16 Equatoreal at Oxford 122 122
- Pearson . 1829 . An Introduction to Practical Astronomy Vol. II , 524 – 524 . London para. 16.
- Rees . 1819 . The Cyclopaedia: Or, Universal Dictionary of Arts, Sciences, and Literature Vol. XVI , London 45 vols article ‘Graduation’, sig. 3Y4r. Also A. Chapman, Dividing the Circle: The Development of Critical Angular Measurement in Astronomy 1500–1850 (Chichester: Ellis Horwood, 1990), 108–17.
- Chapman , A. 1995 . “ Thomas Hornsby and the Radcliffe Observatory ” . In Oxford Figures: 800 Years of Mathematics , Edited by: Flauvel , J. , Flood , R. and Wilson , R. Oxford : Oxford University Press . forthcoming chapter 9
- Howse . 1975 . Greenwich Observatory III: The Buildings and Instruments 82 – 82 . London
- Shuckburgh , George . 1793 . An Account of an Equatorial Instrument . Philosophical Transactions , 83 : 93 – 95 .
- Lax , William . 1808 . On a Method of Examining the Divisions of Astronomical Instruments . Philosophical Transactions , 99 : 232 – 232 .
- It is interesting to see how rapidly the Equatorial Circle developed in the 1790s as the Troughton and Huddart circles addressed the problem of structural rigidity after Ramsden's first—and very influential—essay in the genre for Shuckburgh. See McConnell Anita Instrument Makers to the World, A History of Cooke, Troughton & Simms York 1992 pls on 10 and 17, for illustrations of these instruments.
- December 1810 . Lord Aylesford to Robertson December , London 26 MHS Radcliffe MS 53. There is no evidence to suggest that Robertson ever used the Bird Equatorial Sector, for while two folio volumes of Transits, Zenith Distances, and Zenith Sector Observations that he made survive in MHS Radcliffe MSS 46–47, they contain no reference to the Equatorial.
- Pearson . 1829 . An Introduction to Practical Astronomy Vol. II , 524 – 524 . London The most complete technical treatment of the design and its performance was provided in Rees (footnote 4), XIII (1819), article ‘Equatorial Instrument’, and plates vol. I (1820), section ‘Astronomical Instruments’, plate XVI. J. A. Bennett, Church, State and Astronomy in Ireland: 200 Years of the Armagh Observatory (Belfast, 1990), 38–42. The Armagh Equatorial Circle aimed to achieve a rigid support by fabricating the polar axis from eight large brass cones, although as Robinson admitted, even the heat of the sun ‘totally deranges the Instrument’, Bennett, 42.
- Smyth , W.H. 1851 . Aedes Hartwellianae 244 – 244 . London
- Herschel's , John . 1883 . A Treatise on Astronomy 390ff – 390ff . London gives a good account of how this class of work was performed. Herschel none the less recognised ‘an unknown by comparison with that of a known object’ (99). He took a good equatorial refractor with a 5-inch object glass to the Cape of Good Hope, along with his more famous 20-ft reflector.
- Grant , Robert . 1852 . History of Physical Astronomy 191 – 192 . London gives a detailed account of Galle's procedure of searching for Neptune using the newly prepared Hora XXI chart, along with the Challis micrometric-comparison search.
- Johnson , Manuel J. 1852 . Astronomical Observations made at the Radcliffe Observatory, Oxford, in the Year 1850 Vol. XI , xi – xxxviii . Oxford for Johnson's account of the design and observing procedures of the new heliometer.
Annals of Science
Volume 52, 1995 - Issue 5
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