The Role of Images in Astronomical Discovery
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30 Fourth Earl of Rosse, An Account of the Observations on the Great Nebula in Orion, Made at Birr Castle, with the 3-feet and 6-feet Telescope, between 1848 and 1867, With a Drawing of the Nebula, Philosophical Transactions of the Royal Society of London, 1867, Vol. 158, pp. 57–73.
31 C. Mollan, William Parsons, 3rd Earl of Rosse: Astronomy and the Castle in Nineteenth-Century Ireland, Manchester: Manchester University Press, 2014.
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Fig. 2.5 William Parsons, 1860 portrait by Stephen Catterson Smith. Credit: University of
Cambridge, Institute of Astronomy.
soberly dressed in a watercolour painted around the time of her wedding; but her serious
nature suited William admirably and she concealed huge energy behind her girlish looks.
Also, she was extremely rich.”32 There is evidence that Mary contributed intellectually
to the lord’s multiple ventures in politics, national scientific and local community affairs.
Assisted by his extraordinary wife, Parsons applied his organizing talent, passion and
skills in engineering to build telescopes. He adopted Herschel’s proven technology of large
metal-mirror telescopes and improved their design to realize larger and more ambitious
instruments.33,34
Parsons’ home, Birr Castle in Ireland, soon became a lively research center and observa-
tory, except during the Great Famine (1846–1848), when activities were drastically reduced.
32 Alison, Countess of Rosse, Mary, Countess of Rosse (1813–85), in William Parsons, 3rd Earl of Rosse: Astronomy and the castle in nineteenth-century Ireland, C. Mollan (editor), Manchester: Manchester University Press, 2014, p. 55.
33 C. Mollan, A consummate engineer, in William Parsons, 3rd Earl of Rosse: Astronomy and the Castle in Nineteenth-Century Ireland, C. Mollan (editor), Manchester: Manchester University Press, 2014, pp. 159–209.
34 C. Parsons (editor), The Scientific Papers of William Parsons, Third Earl of Rosse 1800–1867, Cambridge: Cambridge University Press, 2011.
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Part I – Images and the Cosmos
Started in the late 1840s, the observatory functioned actively over more than three decades.
A comprehensive paper reporting on the first years of observing with the Leviathan was pub-
lished in 1861 demonstrating the power and achievements of the giant reflector.35 In 1878,
William’s son, Lawrence Parsons, Fourth Earl of Rosse (1840–1908), published the results
of 30 years of observing at Birr Castle.36 Read today, these publications, together with oth-
ers by Parsons and collaborators, are fascinating as they provide unique insights into the
developing technology and their careful operational and observing processes. Numerous
illustrations of equipment and sketches of “nebulae” with detailed descriptions supplement
these publications.
Parsons’ perspicacious observations had been empowered by his new giant telescope.
Using first a 3-ft (mirror size) telescope based on Herschel’s design, Parsons made many
excellent drawings. Determined to show that a nebula could be resolved into stars and that
angular resolution was related to the mirror size, Parsons built the “Leviathan,” a giant
telescope with a 6-ft mirror. No less important in the discovery process was the obsessive
operational care of the instrument together with the innovative observing techniques Par-
sons and his team had put forward.
The Leviathan, with a 6-ft diameter metal mirror, was a colossal instrument for the time
and remained the largest telescope until 1917. It followed the principles of Herschel’s tele-
scopes, but every aspect of its construction and material used had been greatly improved.
As Herschel had not published technical details on his telescopes, Parsons had to re-invent
most of the complex steps.37 Eager to share his ideas and experiences, he described in
minute detail the steps of making large speculum mirrors and assembling the complex
structures for his big transit telescope. In the extensive article of 1861, Parsons aimed at
giving enough details that a team of competent engineers could repeat the steps and create
their own observatory.38 However, the efforts and challenges described could frighten off
even the most venturous entrepreneurs.
The 3-ft and 6-ft telescopes were strikingly impressive (Fig. 2.6). More innovative were
Parsons’ operational strategies, such as the careful steps taken by the team to ensure that
the mirror quality remained always optimal. The speculum, a metal mirror made of a cop-
per and tin alloy, was subject to quick tarnishing by oxidation. Therefore there were two
mirrors provided for the Leviathan and two as well for the 3-ft telescope, so that one mirror
might be on the polishing machine in the laboratory, while the others were in use.39 Frequent
35 Third Earl of Rosse, On the Construction of Specula of Six-feet Aperture, and a Selection from the Observations of Nebulae Made with Them, Philosophical Transactions of the Royal Society of London, 1861, Vol. 151, pp. 681–745.
36 Fourth Earl of Rosse, Observations of Nebulae and Clusters of Stars Made with the Six-Foot and the Three-Foot Reflectors at Birr Castle from the Year 1848 up to the Year 1878, Scientific Transactions of the Royal Dublin Society, 1878, Vol. II.
37 W. Steinicke, Birr Castle Observations of Non-Stellar Objects and the Development of Nebular Theories, in William Parsons, 3rd Earl of Rosse: Astronomy and the Castle in Nineteenth-Century Ireland, C. Mollan (editor), 2014, Manchester: Manchester University Press, pp. 210–270.
38 Third Earl of Rosse, On the Construction of Specula of Six-feet Aperture, and a Selection from the Observations of Nebulae Made with Them, Philosophical Transactions of the Royal Society of London, 1861, pp. 681–745.
39 G. Johnstone Stoney, in Fourth Earl of Rosse, Observations of Nebulae and Clusters of Stars Made with the Six-Foot and the Three-Foot Reflectors at Birr Castle from the Year 1848 up to the Year 1878, Scientific Transactions of the Royal Dublin Society, 1878, Vol. II, Appendix p. III.
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Fig. 2.6 Photograph of the Leviathan. Credit: University of Chicago Photographic Archive, [apf6–
01245], Special Collections Research Center, University of Chicago Library.
re-grinding and polishing were the most straightforward ways to restore reflectivity. Ameri-
can astronomer Ronald Buta explains that visually the Leviathan had the power of a modern
1-m-class telescope with an aluminium-coated primary glass mirror.
Attentive care was given to the operational procedures, including continuous optical test-
ing during mirror refiguring, just as in modern optical shops. And this was quite a sizeable
enterprise. A comment by George Johnstone Stoney (1826–1911), one of the Birr Castle
telescope night observers, conveys a perspective on the size of the mirrors and the care
taken in their manipulation. Stoney wrote: “The whole had to be lifted from the polishing
machine, and transferred to a large truck, on which it was slowly dragged by twenty-five
or thirty men for a distance of about a quarter of a mile to the Observatory.”40 One gets
additional insight into the scale of things by noting that the Leviathan mirrors, with levers
40 G. Johnstone Stoney, ibid., p. iii.
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Part I – Images and the Cosmos
and carriage, weighed about seven tons. The goal of this demanding maintenance was that
the mirrors had to be of a quality that their figures would match the image finesse delivered
by the atmosphere on the best observing nights. And operating the Leviathan was not for
the weak heart. At nighttime, the giant instrument had to be moved by two men with the aid
of cables and pulleys placed between two large 18-m-high stone piers. The observer was
often positioned in the dark on a high platform, tens of meters above the ground.
George Bond and the Andromeda “Nebula”
At about the same time, the young American astronomer George Bond (1825–1865) was
using the new Harvard 15-inch refractor to study Messier 31. As an object of prominent
interest for testing the new refractor, Bond aimed the instrument in the direction of the con-
stellation of Andromeda. In 1848, he published a fine article with a beautiful drawing of the
“nebula” and described its stars, its clusters of stars and dark bands (Fig. 2.7; compare with
Plate 1.1). He reviewed his recorded historical viewings of the Andromeda “nebula”: “the
only one the discovery of which preceded the invention of the telescope.”41 Commenting
on features already known, Bond also noticed the “sudden termination of the light on the
side of the nebulae preceding in right ascension, . . . a sudden interruption of light, appearing
like a harrow, dark band, . . . exterior to this, with respect to the axis, was another band or
canal.” He described them as “openings” and “canals.” Bond was re-discovering the dust
features John Herschel had reported in 1833.42
Bond’s drawing of the Andromeda Galaxy is quite stunning even compared to modern
photographs. Some remarkable features are noticeable such as the satellite galaxies Messier
32 and NGC 205, and its star-like nucleus. But most innovative for the time was Bond’s
excellent sketching of the two main dust lanes, or “canals,” appearing against what we
know now to be the nearside of the galaxy. The crispness of the observations was likely
enabled by the high contrast provided by the fine optics of the new instrument. Bond gave a
detailed description of the procedure to capture the fine details of the “nebula” that appeared
“fifteen to twenty times” larger than the field of view of the refractor. One had to wait until
Heber Doust Curtis’s photographic work on spirals at Lick Observatory 60 years later to
recognize that the famous dust lanes were not unique to the “great nebula” in Andromeda
(Chapter 3). Bond, also a pioneer of astrophotography, passed away too soon, killed by
tuberculosis at the prime age of 40.
The period between 1855 and 1876 was rich in astronomical sketching and drawing
at Harvard College Observatory. Magnificent engravings of the Moon, Sun, planets and
“nebulae” were produced and published by William Bond, George Bond and Joseph
41 G. P. Bond, An Account of the Nebula in Andromeda, Memoirs of the American Academy of Arts and Sciences, New Series, 1848, Vol. 3, pp. 75–86. Some authors have suggested that Italian astronomer Giovanni Battista Hodierna would have observed Messier 33 as part of his never completed atlas Il Cielo Stellato Diviso in 100 Mappe.
42 J. H. Herschel, Observations of Nebulae and Clusters of Stars, Made at Slough, with a Twenty-Feet Reflector, between the Years 1825 and 1833, Philosophical Transactions of the Royal Society of London, 1833, Vol. 123, pp. 359–505.
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Fig. 2.7 Sketch of the “great nebula” in Andromeda. From Bond (1848), Memoirs of the American
Academy of Arts and Sciences. Courtesy of John G. Wolbach Library, Harvard College Observatory,
2016.
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Part I – Images and the Cosmos
Winlock.43 French artist and astronomer Étienne Léopold Trouvelot, working at Har-
vard Observatory, created a splendid set of sketches of astronomical objects including
“nebulae.”44
Discovering and Imaging Spirals
Following five years of construction, the Leviathan was put into operation in February 1845.
The quality of early observations and findings are testimonies of the power and optical
quality of this telescope and a tribute to the acuity and professionalism of the Birr Cas-
tle observers. One of the research goals of the Rosse team was to resolve “nebulae” into
stars or whatever structures they might show. These drawings were generally a sketch of
a single observing session. A picture or a portrait was built up over time, with pencil on
paper or chalk on black cardboard. “As a collation or composition ordered and arranged by
a routine procedure, therefore, what appears in a final visual result is multiple layers of dif-
ferent nights and days of work – a whole history of looking, discerning, and recording.”45
As mentioned above, object Messier 51 in the constellation of Canes Venatici was on the
program of the first observing sessions.
It was William Parsons himself who first sketched the Messier 51 “nebula” and its spiral
structure, perhaps in March or April 1845, the first portrait ever of a spiral galaxy (see
Fig. 0.2).46 John Herschel presented the early work of the Leviathan and considered it
extraordinary (Fig. 2.8). The event was the Cambridge meeting of the British Association
for the Advancement of Science on 19 June 1845. Herschel, who had produced a rough
sketch of Messier 51 in 1833, recognized the details and the spiral structure drawn by Par-
sons. He praised the new drawing as a major achievement in nebular imaging. Herschel
paid tribute to the Earl of Rosse and his machine with its optical quality. He stated that he
himself was most familiar with the appearance of that particular “nebula” viewed in pow-
erful telescopes, emphasizing that he could appreciate the major step forward in nebular
imagery.
From Herschel’s report, we get an interesting description of William Parsons’ method
of observing and sketching. It is worth quoting at length: “On the Nebula 25 Herschel or 61
[sic] of Messier’s catalogue. Parsons exhibited to the Section what he called his work plan
of this nebula and explained his method. He first laid down, by an accurate scale, the great
features of the nebula as seen in his smallest telescope, which being mounted equatorially,
enabled him to take accurate measurements; he then filled in the other parts, which could
not be distinguished in that telescope, by the aid of the great telescope; but as the equatorial
mounting of this latter was not yet complete, he could not lay these smaller portions down
43 W. C. Bond, G. P. Bond and J. Winlock, Results of Observations, Annals of the Astronomical Observatory of Harvard College, 1876, Vol III.
44 E. L. Trouvelot, Astronomical Sketches Taken at the Harvard College Observatory 1878–18. Originals are held at the Harvard University John Wolbach Library.
45 O. W. Nasim, Observing by Hand: Sketching the Nebulae in the Nineteenth Century, Chicago: University of Chicago Press, 2013, p. 18.
46 M. Hoskin, The First Drawing of a Spiral Nebula, Journal for the History of Astronomy, Vol. XIII, 1982, pp. 97–101.
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Fig. 2.8 John Herschel, from an engraving by William Ward of a painting by H. W. Pickersgill.
Credit: University of Cambridge, Institute of Astronomy.
with rigorous accuracy; yet as he had repeatedly gone over them, and verified them with
much care, though by estimation, he did not think the drawing would be found to need
much future correction.”47 Herschel was himself a fine artist astronomer, as testified by his
beautiful hand drawing of the Large Magellanic Cloud (Fig. 2.9).48
Not surprisingly, M51 continued to be a prime target for the Leviathan observers. The
numerous sketches made later captured all the main features of the Whirlpool Galaxy.
The most faithful and dramatic portrait of the galaxy was published as a full-page plate
in the seminal 1878 paper that assembled all the observing notes made over 30 years by
the Leviathan observers. Messier 51 got its nickname, the “Whirlpool Galaxy,” from the
47 J. Herschel, Report of the Fifteenth Meeting of the British Association for the Advancement of Science held at Cambridge in June 1845, London, 1846, p. xxxvi.
48 D. L. Block and K. C. Freeman, Shrouds of the Night, Masks of the Milky Way and Our Awesome New View of Galaxies, New York: Springer, 2008.
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Part I – Images and the Cosmos
Fig. 2.9 Large Magellanic Cloud as seen with the naked eye from South Africa. Published in 1847,
the superb drawing shows the elongated bar and hints of arms. Courtesy of William Cullen Library,
University of the Witwatersrand, Johannesburg.
spiral structure that appeared as an indication of vortices and motions, A vivid compari-
son can be made by looking at the M51 portrait of 1878, based on the Leviathan telescope
observations, alongside a recent image of the same galaxy produced with the Hubble Space
Telescope (Fig. 2.10 a and b; see also Fig. 0.2). On the reproduction of the drawings exe-
cuted at the telescope, Lawrence Parsons, William’s son, explained: “Into the text have been