The Objective Lens of the Dunsink Ramsden Circle

Chinnici I. , “The relationship between the Ramsden circles at Palermo and Dunsink”, Journal for the history of astronomy, xl (2009), 321–33.

Wayman P. A. , Dunsink Observatory, 1785–1985 (Dublin, 1987), 262–6.

Private communication: Letter of P. A. Wayman dated 16 January 1996.

Ibid.

Wayman , op. cit. (ref. 2), 264.

Lens and glass type as quoted in a list of Dunsink historical items that was drawn up by W. Dumpleton, probably in the first half of the 1990s. Chapman A. (Dividing the circle (Chichester, 1995), 192, note 36) states that by 1790 the use of achromatic lenses was general in circular instruments. A single lens for the Dunsink Circle, delivered in 1808, is therefore interesting. Maybe the large size of this circle, ∼8 ft, rendered a single lens sufficient considering the relatively large focal length, or it might be indicative of the possible earlier origin, as the circle that had been intended for the Duke of Sermoneta (Chinnici, op. cit. (ref. 1), 325).

As in Ussher H. , “Account of the observatory belonging to Trinity College, Dublin”, Transactions of the Royal Irish Academy, i (1787), 3–21.

Chinnici , op. cit. (ref. 1), 326.

Chinnici , op. cit. (ref. 1), 325.

The Meridian Room features half-round ventilation holes (Ussher, op. cit. (ref. 7)).

Chinnici , op. cit. (ref. 1), 326.

Taylor W. B. S. , History of the University of Dublin (London, 1845).

Wayman , op. cit. (ref. 2), 9; Chapman , op. cit. (ref. 6), 117; Brinkley J. , “An account of observations made at the observatory of Trinity College, Dublin, with an astronomical circle eight feet in diameter …”, Transactions of the Royal Irish Academy, xii (1814), 33–75. J. Brinkley was (1790–1826) the second Director of Dunsink Observatory, as the successor of H. Ussher.

Wayman , op. cit. (ref. 2), 21.

Wayman , op. cit. (ref. 2), 284 (Appendix 2).

Chinnici , op. cit. (ref. 1), 327 (Conclusions).

Shuckburgh G. , “An account of the equatorial instrument”, Philosophical transactions, lxxxiii (1793), 67–128; see also Chinnici , op. cit. (ref. 1), ref. 27.