William Herschel and Herschelian Reflectors

Herschel William , “An account of the discovery of two satellites revolving round the Georgian Planet”, Philosophical transactions, lxxvii (1787), 125–9, p. 125.

Lemaire Jacques (fl. Paris, 1720–40), Machines et inventions approuvées par l'Académie Royale des Sciences…, vi (Paris, 1735), 61–3. There seems no way in which William Herschel could have known of Lemaire's work.

On Herschel see for example Hoskin Michael , Discoverers of the universe: William and Caroline Herschel (Princeton, 2011).

RAS MS Herschel W.5/12.1, 5.

Hoskin , Discovers of the universe (ref. 3), 94.

RAS MS Herschel W.2/1.7, 24v; 4/1.5, 462.

As we shall see, the chair was in use before 15/16 August 1784, when Faujas de Saint-Fond visited Herschel: Travels in England, Scotland, and the Hebrides, transl. from the French of B. Faujas Saint-Fond, i (London, 1799), 79.

Hoskin , Discovers of the universe (ref. 3), 95–100. The chair is illustrated in the famous watercolour by Thomas Rackett , ibid., Plate 2.

Saint-Fond Fauja , op. cit. (ref. 7), 79–84.

RAS MS Herschel W.2/1.10, 20.

Herschel William , “On the construction of the heavens”, Philosophical transactions, lxxv (1785), 213–66.

The paper is dated 1 January 1785.

p. 262.

RAS MS Herschel W.2/3.3.

RAS MS Radcliffe Hornsby 78.

RAS MS Herschel W.2/3.6.

Ibid. Eventually Herschel arranged to have two sliders for carrying the eyepiece, one on each side of the tube. This would allow him to use either his left or his right eye. See his letter to J. H. Schroeter, 4 January 1794, RAS MS Herschel W.1/1, 198–9, cited in full in Lubbock Constance A. , The Herschel chronicle (Cambridge, 1933), 214–15.

Herschel William , “Catalogue of one thousand new nebulae and clusters of stars”, Philosophical transactions, lxxvi (1786), 457–99.

The receipt for this reflector, in thirteen packing cases destined for St Petersburg, is dated 25 September 1805, RAS MS Herschel W.5/10. Herschel's instructions for assembly show that it was front-view despite its modest size: “Take out the sliding rack bar VIII, 7, which carries the eye-piece, and place it in the sliding groove at the mouth of the tube…”, ibid., W.5/9, 7. Cf. the description of VIII, 7, in W.5/10, f. 10.

Herschel explained his change of heart in a note added at the end of the catalogue: ” The Front-view is a method of using the reflecting telescope different from the Newtonian, Gregorian, and Cassegrain forms. It consists in looking with the eye glass, placed a little out of the axis, directly in at the front, without the interposition of a small speculum; and has the capital advantage of giving us almost double the light of the former constructions. In the year 1776 I tried it for the first time with a 10 feet reflector, and in 1784 [error for 1783] again with a 20 feet one; but the success not immediately answering my expectations, it was too hastily laid aside. By a more careful repetition of the same experiment I find now, that several other considerable advantages, added to the brilliant light before mentioned, make it so valuable a construction that a judicious observer may avail himself of it at least in all cases where light is more particularly wanted; and from the experience of 30 sweeps, which I have already made with it, I may venture to announce it to be a very convenient and pleasant, as well as useful, way of observing. With regard to the position of objects, it differs from other constructions, by inverting the north and south, but not the preceding and following”.