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This telescope was made by Thomas Grubb of Dublin and was equatorially mounted, with clock movement, under the East dome. The mirror was of speculum metal. The Earl of Rosse made and presented the Observatory with a duplicate of the mirror in 1843. In the Observatory Minute Book for 1843 it was noted that two micrometers were applied to the declination circle, its cast iron axis was replaced with a stronger one, and a machine to polish the specula was completed. The mirror cell was, it is believed, the first ever to employ a compound triangular system of balanced levers to support the main mirror (see Proc. Roy. Soc., 135, p.iv, 1932 and H.C. King in 'The History of the Telescope', Griffin & Co., 1955). T.R. Robinson spoke well of this telscope as the resolving power was good enough to separate some difficult double stars (see Phil. Trans. Roy. Soc., 159, 132, 1869). The mirror was re-figured in 1871 by Grubb. A good observation of the 1882 transit of Venus was obtained (see Copernicus, 3, 18, 1882).
Last Revised: 2015 January 8th