Next time you visit the Royal Society Library, do take a look at our latest exhibition Silent Harmony: Astronomy at the Royal Society. This takes a whistle-stop tour through 400 years of mankind’s quest to chart the heavens, from Galileo’s Sidereus nuncius or ‘starry messenger’ (1610), the first published work to incorporate scientific observations by telescope, to Bernard Lovell’s diary of the construction of the Jodrell Bank radio telescope in the 1950s.

One of my favourite items in the exhibition is a series of small photographs of a large telescope constructed at Birr Castle in Ireland. Made for Royal Society President Lord Rosse (William Parsons), this extraordinary reflecting telescope with a 72-inch mirror was first brought into use in 1845, its epic scale earning it the nickname ‘the Leviathan of Parsonstown’. These photographs were turned into illustrations for a paper by Rosse, ‘On the Construction of Specula of Six-Feet Aperture; and a Selection from the Observations of Nebulae Made with Them’ (1861).


The Leviathan of Parsonstown, c.1861 © The Royal Society, PT/62/8


Captured inside the telescope’s tube in the left hand image above is Lord Rosse, with his sons Richard Clere (standing foreground) and Charles Algernon (seated) alongside two other finely-dressed gentlemen.

Lord Rosse was especially interested in nebulae, at the time a catch-all term referring to ‘fuzzy objects’ in the night sky. Rosse wanted to increase the light-gathering power at his disposal in order to view such objects more clearly, and this power depends on the diameter or aperture of the lens or mirror used. Having previously succeeded in casting a three foot mirror, Rosse, with the assistance of the labourers on his estate, constructed not one but two six-foot mirrors, allowing one mirror to be used whilst the other was swapped out for polishing.

The photographs above were captured by Countess Mary of Rosse, who experimented with photographic techniques such as daguerreotypes and a wax paper process; the special dark room constructed at the castle for this purpose remains open to visitors today.

Lord Rosse catalogued a large number of nebulae, including some later recognized as galaxies – gravitationally-bound systems of stars, gas and dust. Rosse’s Leviathan was the first telescope to reveal the spiral structure of a galaxy, M51 or the ‘Whirlpool Galaxy’. Debates over the true characteristics of nebulae continued for many years, and were not resolved until the 1920s when Edwin Hubble recognized some of these ‘fuzzy objects’ to be galaxies like our own Milky Way.


Figures from ‘Observations on the Nebulae’ by Lord Rosse, (Phil. Trans. vol 140, 1850), including top left, the M51 spiral galaxy © The Royal Society


The Leviathan of Parsonstown remained the world’s largest telescope for over 70 years, until the opening of the 100-inch Hooker Telescope at the Mount Wilson Observatory in America, used by Hubble himself. Having fallen into disrepair, Rosse’s telescope underwent restoration and in 1999 became operational again, its incredibly heavy alloy mirrors replaced by aluminium.

After exploring the Silent Harmony exhibition, do pop into the Library where we can direct you to some of our latest printed works on the history of astronomy and help you to view related historical items from our collections. Audio from a lunchtime lecture on the Leviathan is also available to listen to online from the comfort of your armchair.


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