Minutes of the States-General of the Netherland, 2 October 1608. The Hague, Algemeen Rijksarchief, MSS. “Staten-Generaal”, xxxiii, 169r. See Van HeldenA., “The Invention of the Telescope”, Transactions of the American Philosophical Society, forthcoming.
2.
Johannes Kepler gesammelte werke (Munich, 1938–), iv, 387–9.
3.
Ibid., 388–9. Galileo discussed the projection of the Sun's image through a Galilean telescope in his second letter on sunspots (Le opere di Galileo Galilei. Ristampa della Edizione Nazionale (Florence, 1929–39), v, 136–7). In tracing sunspots on a paper on which the Sun's image is projected, the use of a Galilean telescope will result in a tracing in which top and bottom are inverted but left and right are correct, while the use of a Keplerian telescope will give a tracing in which left and right are inverted but top and bottom are correct. In either case the paper has to be held up to the light and the image transferred to the back of it for all the orientations to be correct. The only advantage of the Keplerian configuration is in the continuous adjustment of the telescope to keep the Sun's image on the paper: One does not have to remind oneself to do the opposite of what seems to be indicated.
4.
Rosa ursina (Bracciano, 1626–30), 129v–130r.
5.
Van HeldenA., “The ‘Astronomical Telescope’, 1611–1650”, Annali dell' Istituto e Museo di Storia della Scienza, forthcoming.
6.
Novem stellae circa Jovem (Louvain, 1643), 9.
7.
Oculus Enoch et Eliae (Antwerp, 1645), part 1, 336–56. Rheita's secreta is on p. 356.
8.
Ibid., 339.
9.
Cavendish to Pell, 20 November 1641 (o.s.), in HalliwellJames Orchard (ed.), A collection of letters illustrative of the progress of science in England (London, 1841, reprinted London, 1965), 74.
10.
Ibid., 72–74. Halliwell printed here six letters from Cavendish to Pell dated between 26 June 1641 and 5 February 1641/2 (o.s). Apparently unaware that it was the custom to begin the new year on 25 March, Halliwell mixed up the chronological order of the letters.
11.
Oeuvres de Descartes publiées par Charles Adam & Paul Tannery (Paris, 1897–1913), iii, 585–6.
12.
Halliwell, op. cit., 83.
13.
Ibid.
14.
Ibid., 85.
15.
Ibid., 87. In order to avoid confusion I have rendered all dates in the new style in the text of this article. Note that Halliwell made the same mistake (see ref. 10) in printing the letters from Cavendish to Pell written between 26 July 1644 and 27 June 1645 (o.s.), 76–88.
16.
Ibid., 77–78.
17.
Oldenburg to Hartlib, 23 July 1659 (o.s). The correspondence of Henry Oldenburg (Madison, London, 1964–), i, 288.
18.
British Museum, MSS. “Sloane” 651, 169–171. This document (in Latin) was reproduced in facsimile by Thomas H. Court and Moritz von Rohr in “New Knowledge of Old Telescopes”, Transactions of the Optical Society, xxxii (1930–31), 113–22, pp. 118–9.
19.
Oeuvres complètes de Christiaan Huygens (The Hague, 1888–1950), hereafter cited as O.C., i, 215, 224.
20.
O.C., i, 308–9. This is a letter with instructions for assembling a telescope sent by Wiesel. Although Wiesel described the instrument in question as a telescope with six lenses, one of these is merely a coloured glass for observing the Sun.
21.
O.C., xv, 10–15.
22.
O.C., ii, 7. Huygens mentions here that with this instrument he could see the entire Moon and a bit more at one time.
23.
Huygens was always hesitant to add more lenses to his telescopes. For a long time he preferred an erecting mirror (at 45° to the optical axis) to an erector lens, even though terrestrial telescopes of this construction showed left and right reversed. He began the passage in his Dioptrica in which his compound eyepiece is described with the words: “Quanquam lentes non frustra sint multiplicandae …” (O.C., xiii, 253, 463).
24.
O.C., ii, 7; xv, 56, 60, 350.
25.
O.C., ii, 362; xv, 230.
26.
O.C., ii, 358.
27.
O.C., iii, 417.
28.
O.C., ii, 521.
29.
O.C., iii, 58.
30.
O.C., iii, 45–46.
31.
British Museum, MSS. “Sloane” 1326, 23r–24v. This letter, “transcribed into modern English”, was first published by Court and Von Rohr, op. cit. (ref. 18), 121.
32.
O.C., xxii, 568–76. This is Huygen's journal of his stay in England. See also O.C., iii, 265–7.
33.
O.C., iii, 445.
34.
O.C., iii, 271–2; xxii, 575.
35.
O.C., iii, 445.
36.
The first mention of these mirrors was in 1654, O.C., i, 242. See also O.C., xiii, 264, note 3.
37.
When his father asked him to make a telescope with an erecting mirror for a highly placed person in Paris, Huygens sent such an instrument in May 1662 (O.C., iv, 132–3). In September he sent another instrument which had three lenses and a mirror (O.C., iv, 228–9). At that time he told his brother Lodewijk that he could have the first one “… car d'en faire present a quelqu'autre il n'a garde, a cause du secret de l'invention” (O.C., iv, 224).
38.
O.C., iv, 242–3.
39.
O.C., iv, 250.
40.
O.C., iv, 125.
41.
O.C., iv, 266–9.
42.
O.C., vi, 48. Huygens described the construction of one of Campani's terrestrial telescopes in his Dioptrica, O.C., xiii, 469–73, 607.
43.
O.C., xiii, 252.
44.
O.C., xiii, 252–3.
45.
O.C., xiii, L, note 4.
46.
E.g., BarlowBoris V., The astronomical telescope (London & New York, 1975), 60–61.
47.
In his Traité de la lumière of 1692 Huygens did not treat colours.
48.
On the dating of the various drafts of his posthumous Dioptrica, see O.C., xiii, I–XIII.
49.
O.C., xiii, 252.
50.
O.C., xiii, 262–4.
51.
O.C., xiii, L. Not until after 1685 did Huygens treat the size of the field theoretically (ibid., 450–3, 457–61, 468–73).
52.
NorthJohn, “Thomas Harriot and the First Telescopic Observations of Sunspots”, in ShirleyJohn W. (ed.), Thomas Harriot, Renaissance scientist (Oxford, 1974), 129–65, 146–7.
53.
Thomas Harriot had a 50-powered Galilean telescope, but it is mentioned only once in the record of his observations (ibid., 142). This telescope could not have had a field of view much larger than 5'. Note that such a small field was an even greater handicap in terrestrial observations. A telescope with a field of 15′ will show an area of about 12 feet at 1000 yards, while one with a field of 5′ will only show an area of about 4 feet at this distance.
54.
O.C., ii, 7; xv, 56, 60, 350.
55.
In his Novae coelestium terrestriumque rerum observationes (Naples, 1646), Francesco Fontana mentioned telescopes of 50 Neapolitan palms, i.e., about 40 feet (p. 21). Eustachio Divini mentioned telescopes of up to 45 Roman palms (about 35 feet) in length in an advertising sheet in 1649. See Bullettino di bibliografia et di storia delle scienze matematiche e fisiche, xx (1887), facing p. 614. From 1660 to 1662 Huygens was engaged in a controversy with Divini in which Divini claimed that his telescopes were better than those of Huygens because they were longer. See O.C., xv, 406–14.
56.
O.C., iv, 152.
57.
I thank Dr Marie Boas Hall for calling this letter to my attention.
58.
In the margin of this copy is a little sketch of Saturn as observed by Wiesel.
59.
This telescope, then, showed things inverted, and this raises a question as to the function of the “great ocular glas” in the second draw tube.
