J. S. Plaskett and the Modern Large Reflecting Telescope

Robert W. Smith refers to instruments as “engines of discovery” in his insightful analysis of the historical literature of astronomical instrumentation: “Engines of discovery: Scientific instruments and the history of astronomy and planetary science in the United States in the twentieth century”, Journal for the history of astronomy , xxviii (1997), 49–77.

That the Victoria telescope was the prototype for conventional large reflectors may be well known, but is rarely if ever mentioned in the literature. One exception is Richard Learner , Astronomy through the telescope (New York, 1987), 147.

In this article, I refer only to ground-based telescopes. Space-based telescopes, although similar in their optical components to ground-based telescopes, require very different technological solutions for protection, power, control and data systems. See Robert W. Smith , The space telescope: A study of NASA, science, technology, and politics (New York, 1989).

In the period covered by this study, only four very large telescopes were built: The 100-inch at Mount Wilson (1918), the 200-inch at Palomar Mountain (1948), the 120-inch at Lick (1959), and the 102-inch at the Crimean Astrophysical Observatory (1960). Although astronomers today refer to mirror sizes in metres, inches were used during this period and to convert them would be anachronistic.

The standard work is Henry C. King , The history of the telescope (London, 1955). A still useful popular overview of instrumentation is Miczaika G. R. William M. Sinton , Tools of the astronomer (Cambridge, Mass., 1961), which replaced the earlier volume by George Z. Dimitroff James C. Baker , Telescopes and accessories (Philadelphia, 1945). See, also, Bennett J. A. , “The giant reflector, 1770–1870”, in Forbes E. G. (ed.), Human implications of scientific advance (Edinburgh, 1978), 553–8.

Grubb's Melbourne telescope had a cross-axis English equatorial mounting and a Cassegrain optical system, both of which became a standard in the twentieth century, but the telescope was deemed a failure. See King , History (ref. 5), 264–7.

Thomas Grubb was the first to employ what he called an “equilibrated lever” system, on a 15-inch reflector made in 1835 for Romney Thomas Robinson at Armagh. Lord Rosse , following Grubb's lead, designed a massive support system which include ball-and-socket joints and a complex of triangles and weighted levers. See Bennett J. A. , Church, state and astronomy in Ireland: 200 years of Armagh Observatory (Belfast, 1990), and Glass I. S. , Victorian telescope makers: The lives and letters of Thomas and Howard Grubb (Bristol, 1997).

Common described his efforts in the Memoirs of the Royal Astronomical Society , 1 (1890–91), 113–204. See also Dyson's Frank obituary of Common in the Monthly notices of the Royal Astronomical Society , xliv (1903–4), 274–8. Common was not so prescient about future large reflectors. While he believed that 8- or 9-foot mirrors would be possible, he expected they would by used as visual reflectors (with focal ratios of about f/12) and would have to be built with altazimuth mountings like Herschel's! See Common , “On the best form of mounting for a large reflector”, ibid. , liii (1892–93), 19–22.

A 36-inch (1879) that eventually found its way to the Lick Observatory as the Crossley Telescope, a 30-inch for Norman Lockyer (1888), a 36-inch for the Solar Physics Observatory in South Kensington (1889), and a 30-inch for the Khedival Observatory in Helwan , Egypt (1905).

Howard Grubb Sir produced a 30-inch for Greenwich in 1897 (mirror by Common); Zeiss a 33-inch for La Plata in 1896; Brashear a 37-inch for Lick's southern station in 1904, a 30-inch for the Allegheny Observatory in 1906, and a 37.5-inch for the University of Michigan in 1911; Clark a 44-inch for the Lowell Observatory in 1910.

Although André Danjon André Couder aver that “Plus décisif fut le rôle de l'Anglais Common, à qui l'on doit le prototype des grands instruments contemporains”, Lunettes et téléscopes (Paris, 1935), 691.

On Ritchey , see Donald E. Osterbrock , Pauper and prince: Ritchey, Hale, and big American telescopes (Tucson, 1993). For Hale , consult Helen Wright , Explorer of the universe: A biography of George Ellery Hale (New York, 1966).

Howard Grubb , “On great telescopes of the future” (abstract), Scientific proceedings of the Royal Dublin Society , n.s., i (1878), 1.

George E. Hale , “On the comparative value of refracting and reflecting telescopes for astrophysical investigations”, Astrophysical journal , v (1897), 119–31.

Ritchey G. W. , “A support system for large specula”, ibid. , 143–47.

He outlines his methods in “On the modern reflecting telescope, and the making and testing of optical mirrors”, part of vol. xxxiv (Washington, D.C., 1904) of Smithsonian Contributions to Knowledge. .

[ David Gill ], “Telescope”, Encyclopaedia Britannica , 11th edn (Cambridge, 1911), xxvi, 557–72.

On Plaskett's career, see Jarrell R. A. , The cold light of dawn: A history of Canadian astronomy (Toronto, 1988) and “The birth of Canadian astrophysics: J. S. Plaskett at the Dominion Observatory”, Journal of the Royal Astronomical Society of Canada , lxxi (1977), 221–33.

For background, consult Jarrell R. A. , “The origins of the Dominion Observatory, Ottawa”, Journal for the history of astronomy , xxii (1991), 45–53, and “Origins of Canadian government astronomy”, Journal of the Royal Astronomical Society of Canada , lxix (1975), 71–85.

His experiments in spectrograph design were published in: Canada, Department of the Interior, Report of the Chief Astronomer, 1908 (Ottawa, 1910), 86–99; Astrophysical journal , xxix (1909), 290–300; Journal of the Royal Astronomical Society of Canada , ii (1908), 157–8; iii (1909), 190–209, 287–305; iv (1910), 333–14.

Canada, Department of the Interior, Report of the Chief Astronomer, 1911 (Ottawa, 1915), 134–5.

Plaskett J. S. Campbell W. W. , 7 November 1910. Lick Observatory Archives.

Report of the Chief Astronomer, 1911 (ref. 21), 105.

Schlesinger Frank Plaskett J. S. , 7 October 1910. National Archives of Canada (NAC), RG 48, vol. xlvii.

Schlesinger Plaskett , 22 October 1910. NAC, RG 48, vol. xlvii.

Plaskett J. S. , “Description of the building and equipment”, Publications of the Dominion Astrophysical Observatory , i (1922), 7–103.

Frost E. B. Plaskett , 11 May 1912. NAC, RG 48, vol. xlviii.

Schlesinger Plaskett , 26 June 1912. NAC, RG 48, vol. xlvii.

Memorandum, King W. F. Buskard Mr , 12 September 1912. NAC, RG 48, vol. xlix.

Plaskett Adams W. S. , 21 November 1912. George Ellery Hale Papers, microfilm 95. Adams to Plaskett, 11 December 1912. NAC, RG 48, vol. xlvi.

Political considerations favoured siting the new telescope in Ottawa , but site testing by one of Plaskett's staff, Harper W. E. , showed that Victoria was far superior. Plaskett's American correspondents agreed and he was able to override his opponents. Initial plans appeared in King W. F. , “The new reflecting telescope for the Dominion Observatory”, Journal of the Royal Astronomical Society of Canada , vii (1913), 216–28.

Apart from Ritchey's telescopes, there were only moderate-sized reflectors with apertures less than 40 inches as models. The Common telescope at Harvard was not functional, the Melbourne telescope fallen into disuse, and the 47-inch Paris reflector of Martin practically useless.

Copies are in NAC, RG 48, vol. xliv.

Cory W. W. King , 2 April 1913. NAC, RG 48, vol. xliv.

Petitdidier O. King , 23 May 1913. NAC, RG 48, vol. xliv.

Ritchey G.W. King , 24 Aug 1912; Pickering E. C. King , 14 August 1912. NAC, RG 48, vol. xliv.

Ritchey King , 22 March 1913. NAC, RG 48, vol. xliv.

Here again is the inconsistent use of “modified German mounting”, which in this case refers to the cross-axis mounting.

Pickering E. C. King , 10 Mar 1913. NAC, RG 48, vol. xliv.

Schlesinger King , 12 Mar 1913. NAC, RG 48, vol. xliv.

Curtis H. D. Plaskett , 13 October 1913. NAC, RG 48, vol. xlviii.

Adams W. S. Plaskett , 5 May 1913. NAC, RG 48, vol. xlvi. Adams was referring to Perrine's contract with Warner Swasey for the 60-inch reflector for Argentina.

Plaskett , “Description” (ref. 26), 9.

Curtiss R. H. Plaskett , 13 May 1913. NAC, RG 48, vol. xlvii.

Plaskett , “Description” (ref. 26), 9. Exactly why he was impressed is not clear. The telescope was not much of a success and its mounting was replaced by Fecker in the 1930s.

Grubb H. King , 1 April 1913. NAC, RG 48, vol. xliv.

Grubb King , 21 May 1913. NAC, RG 48, vol. xliv.

Plaskett , “Description” (ref. 26), 10.

Grubb King , 11 June 1913. NAC, RG 48, vol. xliv.

Plaskett King , 17 July and 25 July 1913. NAC, RG 48, vol. xliv.

Sampson had corresponded with Ritchey since 1911 and supported his ideas. One wonders whether this was a factor in Sampson's criticism of Grubb .

Plaskett , “Description” (ref. 26), 19.

King Alvan Clark Sons , 16 April 1913; identical letter of same date to Brashear. NAC, RG 48, vol. xlix. McDowell J. B. King , 19 April 1913, and Carl Lundin A. R. King , 24 April 1913, ibid. .

Several copies are in Dominion Astrophysical Observatory (DAO), File 686. This file has been transferred to the NAC.

Plaskett , “Description” (ref. 26), 11.

Ibid. , 37.

“Specification & estimate from Sir Howard Grubb”, 4. Further details of his scheme can be found in Howard Grubb Sir , “Improvements in equatorial telescope mountings”, Scientific proceedings of the Royal Dublin Society , n.s. xiii (1912), 223–8.

Carl A. R. Lundin King , 16 August 1913. NAC, RG 48, vol. xlix.

Memorandum, King Cory W. W. , 6 October 1913. NAC, RG 48, vol. xliv. Several months later, the Carl Zeiss firm wrote to King , claiming it could now obtain sufficiently-large disks, quoting DM 281,000 for a 72-inch, plus DM 72,000 for a dome.

Grubb King , 21 July 1913. DAO, File 669. This file has been transferred to the NAC.

Their correspondence is in NAC, RG 48, vol. xlvii.

The Allegheny Observatory possessed a 31-inch Brashear reflector, which Plaskett would have seen in 1906 when it was installed; by the time tendering for the 72-inch was underway, Brashear was completing the 30-inch Thaw refractor for Allegheny.

Plaskett King , 5 November 1913. DAO, File 686.

Plaskett J. S. , The Dominion Astrophysical Observatory, Victoria, B.C. (Ottawa, 1923), 29.

Plaskett J. S. , “Edward P. Burrell”, Publications of the Astronomical Society of the Pacific , xlix (1937), 141–3.

I have found no evidence of any astronomer denigrating its performance. Young R. K. , who used it for several years, employed the same design for the David Dunlap Observatory telescope.

Judging from drawings and photographs, the ratio of the length of the tube to the polar axis was 2:1 for Melbourne, 1:1.1 for Ann Arbor and 1:1.3 for Victoria. The declination axis was nearly central on the polar axis for Victoria , but located close to the lower bearing of the polar axis in the other two. When the tube was parallel to the polar axis, the mirror cells of the older telescopes projected below the lower end of the polar axis. In the Victoria design, there was ample clearance for a spectrograph as long as eight feet.

Plaskett , “Description” (ref. 26), 11. This was a shot at Ritchey . Of course, Plaskett was on good terms with Hale Adams , which may have coloured his views of Ritchey . He does admit that the fork-mounted 60-inch was compact, lighter and required a small dome, but having mercury flotation, it could not reach the entire sky and Ritchey's mounting was not “seriously” considered. Ibid. , 10.

Ibid. , 72.

Delloyé J. Ambrose Swasey , 13 June 1914. NAC, RG 48, vol. xlv.

Telegram, Plaskett King , 23 August 1914. NAC, RG 48, vol. xlv.

Plaskett , “Description” (ref. 26), 19.

McDowell J. B. King , 6 August 1915. NAC, RG 48, vol. xlv.

Howard Sir relocated to England in 1918; on his death in 1925, Charles Sir Parsons assumed the firm, erecting a new works in Newcastle. Although the firm was called Howard Grubb Sir , Parsons and Company, it was commonly referred to as Grubb-Parsons. For background, see Glass I. S. , Victorian telescope makers (ref. 7).

Clyde Fisher , “James Walter Fecker builder of telescopes March 4, 1891 — November 11, 1945”, Popular astronomy , liv (1946), 17–19.

Clifford C. Crump , “The Perkins Observatory of the Ohio Wesleyan University”, Popular astronomy , xxxvii (1929), 553–9.

Crump C. C. Plaskett , 23 September 1920. NAC, RG 48, vol. xlvi.

Crump Plaskett , 26 July 1926. NAC, RG 48, vol. xlvi.

Crump Plaskett , 22 June 1922. NAC, RG 48, vol. xlvi.

The mounting and dome were completed by 1925 and Crump borrowed one of Harvard's 60-inch Common disks for tests.

Stetson H. Harper W. E. , 22 June 1926. NAC, RG 48, vol. xlvi.

Stetson Plaskett , 12 October 1931. NAC, RG 48, vol. xlvi.

Struve O. Plaskett , 11 July 1933. DAO, Struve Correspondence File. This file has been transferred to the NAC. Struve became involved with the Perkins Observatory because its director. Stetson , was not an active researcher and Yerkes had no immediate prospect of a large reflector of its own. A cooperative arrangement was worked out and Struve despatched Franklin Roach to Ohio as observer. Research continued at Perkins later under Yerkes alumni Bobrovnikoff N. T. Hynek J. A. .

Rufus Carl W. , “Astronomical observatories, Ann Arbor”, in Wilfred B. Shaw (ed.), The University of Michigan: An encyclopedic survey (Ann Arbor, 1951), ii, 473ff.

Curtiss Plaskett , 5 October 1915. NAC, RG 48, vol. xlvii.

For an overview, see David S. Evans , “Astronomical institutions in the southern hemisphere, 1850–1950”, in Owen Gingerich (ed.), The general history of astronomy. Astrophysics and twentieth-century astronomy to 1950: Part A (Cambridge, 1984), 153–65, and Under Capricorn: A history of southern hemisphere astronomy (Bristol, 1988). On Perrine , consult John Hodge , “Charles Dillon Perrine and the transformation of the Argentine National Observatory”, Journal for the history of astronomy , vii (1977), 12–25.

Plaskett first heard the news from Schlesinger. Schlesinger Plaskett , 7 June 1912. NAC, RG 48, vol. xlvii.

“Sixty-inch reflector for the Argentine National Observatory”, Popular astronomy , xxx (1922), 593–7.

Enrique Gaviola , “The Cordoba Observatory”, Sky & telescope , i (1942), 3. It is unclear when the mounting was designed, as opposed to constructed. Judging from the photograph accompanying the article, it seems far less elegant than either Ritchey's 60-inch mounting or the Victoria mounting.

See David S. Evans Mulholland J. Derral , Big and bright: A history of the McDonald Observatory (Austin, 1986); also consult Donald E. Osterbrock's Yerkes Observatory, 1892–1950: The birth, near death, and resurrection of a scientific research institution (Chicago, 1997), chap. 8.

Otto Struve , “The W. J. McDonald Observatory of the University of Texas”, Publications of the Astronomical Society of the Pacific , lv (1943), 123–35. Frost had suggested obtaining a 60- or 72-inch reflector for Yerkes as early as 1928; when Struve succeeded him as director in 1932, it was high on his priority list. See Evans Mulholland , Big and bright (ref. 90), 22–23.

Struve O. Plaskett , 20 October 1932; Plaskett to Struve, 29 October 1932. DAO, Struve Correspondence File.

Stilwell C. J. Plaskett , 20 April 1933. DAO, Struve Correspondence File.

Struve reported the same story (“that this is a lie is obvious”) to Plaskett, identifying Ritchey as the likely culprit. Struve had decided at that point to accept Warner Swasey for the entire telescope, but also wanted a letter from Plaskett supporting his choice. Struve Plaskett , 26 June 1933; Plaskett's reply, 29 June 1933. DAO, Struve Correspondence File.

Plaskett Bliss Philip , 6 May 1933. DAO, Struve Correspondence File.

Struve wanted to forgo having a Newtonian focus. Plaskett argued that guiding from the prime focus was difficult at Victoria , and with an f/4 primary, would be even more so. He suggested adding the Newtonian in the design stage rather than having to retrofit the telescope if prime focus guiding turned out to be too difficult. The advice was ignorEd. Plaskett Struve , 5 July 1934. DAO, Struve Correspondence File.

Plaskett Struve , 9 January 1934. DAO, Struve Correspondence File.

Solon I. Bailey , The history and work of Harvard College Observatory 1839 to 1927 (New York, 1931), 47f.

Carl Zeiss suggested a “radical” design. Young found little difference between the designs of Fecker , who also tendered, and Grubb-Parsons; a key factor was the recent rise in the American dollar and drop in sterling, making a British contract more reasonable. Young R. K. , “The 74-inch telescope of the David Dunlap Observatory”, Journal of the Royal Astronomical Society of Canada , xxviii (1934), 97–119. For background on the observatory, see Chant C. A. , Astronomy in the University of Toronto: The David Dunlap Observatory (Toronto, 1954).

Young , “The 74-inch telescope” (ref. 99), 104.

For specific technical details, see “74-in. reflecting telescope for Toronto University”, Engineering , 9 March 1934, 281–3; 30 March 1934, 365–6; 20 April 1934, 447–50.

“The 74 in. Pretoria reflector”, The engineer , 12 Sept. 1938, 298–301; 23 Sept. 1938, 326–8; 30 Sept. 1938, 353–4.

The initial staff at Pretoria Redman R. O. Evan Williams , wanted to concentrate on stellar spectroscopy along the lines of Victoria. When the telescope was finished, and after Williams's death and Redman's removal to Cambridge, Evans D. S. carried on a B-star programme to complement the work of the DAO. Redman had cut his teeth under Plaskett at the DAO and had married the sister of the wife of his fellow spectroscopist, Beals C. S. . By the time Redman was planning his programme, Beals was Dominion Astronomer in Canada.

Olin J. Eggen , “The Australian Commonwealth Observatory”, Sky & telescope , xv (1956), 340–3.

Jean Dufay Charles Fehrenbach , “France's Haute Provence Observatory”, Sky & telescope , xxii (1961), 4–9.

See Barlow B. V. , The astronomical telescope (London, 1975) for design features of very large telescopes.

For example, at Victoria , the prime focus was virtually never used and the Newtonian only briefly by Helen S. Hogg for globular cluster photography. The rest of the staff concentrated upon spectroscopy of O and B stars; a similar programme prevailed at Toronto (again, except for Helen Hogg's work). The original research programme for the Pretoria telescope was along the same lines as Victoria's. Nebular spectroscopy or faint-object photography, featured at Mount Wilson Palomar , employed Newtonian or prime foci.

Aden B. Meinel , “Design of reflecting telescopes”, in Gerard P. Kuiper Barbara M. Middlehurst (eds), Telescopes (Chicago, 1960), 25–42.

This table was compiled from the appendix to Kuiper Middlehurst , Telescopes (ref. 108), supplemented by a variety of articles. A shorter version is provided by Barbara L. Welther , “The world's largest telescopes, 1850–1950”, in Gingerich (ed.), op. cit. (ref. 86).