| RefNo | Title | Date |
| EC/1860/15 | Main, Robert: certificate of election to the Royal Society | |
| MC/7/191 | Letter from R [Robert] Main, Radcliffe Observatory, Oxford, to J Park Harrison | 29 March 1865 |
| MC/7 | Volume 7 of miscellaneous correspondence regarding business matters, sent to the Royal Society | 1864-1866 |
| AP/47/4 | Observations, 'Lunar curves of m [mean] temperature at Greenwich' by J Park Harrison | 1865 |
| HS/12/280 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 21 September 1868 |
| HS/12/281 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 30 September 1868 |
| HS/24/227 | Copy letter, from Sir John Herschel to Robert Main, dated at Collingwood | 19 September 1868 |
| HS/12/284 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 29 August 1870 |
| HS/12/282 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 1 October 1868 |
| HS/12/277 | Letter, from Robert Main to Sir John Herschel, dated at Greenwich | 6 April 1859 |
| HS/23/344 | Copy letter, from Sir John Herschel to Robert Main, dated at Collingwood | 25 October 1861 |
| HS/12/276 | Letter, from Robert Main to Sir John Herschel, dated at Greenwich | 5 April 1853 |
| HS/12/285 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 2 September 1870 |
| HS/24/229 | Copy letter, from Sir John Herschel to Robert Main, dated at Collingwood | 29 September 1868 |
| HS/12/283 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 26 January 1869 |
| HS/24/240 | Copy letter, from Sir John Herschel to Robert Main, dated at Collingwood | 24 November 1868 |
| HS/12/278 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 21 October 1861 |
| HS/12/279 | Letter, from Robert Main to Sir John Herschel, dated at Radcliffe Observatory | 29 January 1863 |
| HS/23/342 | Copy letter, from Sir John Herschel to Robert Main, dated at Collingwood | 17 October 1861 |
| HS/24/248 | Copy letter, from Sir John Herschel to Robert Main, dated at Collingwood | 30 January 1869 |