The transit of Venus

An animation of Jules Janssen’s photographic sequence showing the transit of Venus, 8 December 1874

5-6 June 2012, will see the transit of the planet Venus across the face of the Sun. It’s worth looking out for, not least because the next time it occurs won’t be until 10 December 2117.

It was certainly something to look out for on 8 December 1874, when French scientist Pierre-Jules-César Janssen (1824-1907), a keen observer of eclipses (and now most famous as the discoverer of Helium), decided to try and capture the motion of Venus crossing the sun through sequence photography, something now recognised as one of the key milestones on the route to cinematography itself.

Janssen’s purpose was not to capture motion for its own sake, however. What was of particular interest to astronomers was capturing the very point of contact between planet and sun, which was needed to help determine solar distance more precisely. Since the exact moment could not be predicted, making a single-shot photograph strategy a hazardous one, Janssen planned to take a rapid sequence of photographs – or at least as rapid as the technology of 1874 would allow. This he achieved by constructing a ‘revolver photographique’ – a camera, somewhat similar in concept to a Colt revolver, driven by a clockwork-driven Maltese Cross-like mechanism capable of taking forty-eight exposures on a Daguerrotype plate over a period of seventy-two seconds. Daguerrotypes were becoming an antiquated technology, but, as Stephen Herbert explains on Who’s Who in Victorian Cinema:

… the metal plate ensur[ed] an absence of halation (flare) that could have been a problem if a glass plate had been used – and a wet plate would in any case have been inconvenient to use in such a camera. With the sun as the source there was no shortage of light, so the ‘slow’ daguerreotype process was ideal.

Janssen’s revolver photographique, pointed at a heliostat (a clockwork-operated mirror following the movement of the sun), as published in La Nature in 1875. The operator was the Brazilian astronomer d’Almeida

Janssen journeyed to Japan to take his photographic sequence (the actual operator of the revolver was a Brazilian, Francisco Antônio d’Almeida), while inspiring several British expeditions with the same purpose to use similar photographic apparatus constructed by J.H. Dallmeyer and using a form of dry plate photography (the expeditions were based in Egypt, India, Australia, Rodrigues, Honolulu, New Zealand and the Kerguelen Islands). Janssen presented the results to the Société Française de Photographie in 1875 – as still images, that is, not of course as a projected sequence, the technology for which was several years away from being invented. We can animate the sequence now, and all six seconds of it can be seen in the video above. The conditions under which Janssen ‘filmed’ were not ideal, it being a cloudy day, and the images were touched up slightly, making Janssen perhaps as much a proto-animator as he was a proto-cinematographer. (Although Janssen definitely produced a successful series of photographs, some suggest that the images we have today are from an earlier simulation made by Janssen to test his equipment).

Janssen’s work inspired others to capture scientific subjects through sequence photography, notably the physiologist Etienne-Jules Marey, and he lived long enough not only to see cinematography becaome a reality, but to appear in two early Lumière films: Débarquement du Congres de Photographie a Lyon and M. Janssen causant avec M. Lagrange, filmed on 11 June 1895.

The transit of Venus as photographed by Professor David Peck Todd on 6 December 1882

Jules Janssen’s capturing of the transit of Vanus as a sequence of images invariably features in pre-histories of cinema (or histories of pre-cinema). The British astronomers using similar technology are seldom mentioned, and in none of the histories will you find mention of the next transit of Venus, which took place on 6 December 1882, and which was also captured in sequence on photographic plates by astronomers ahead of eventual motion picture technology.

How many did so in 1882 I do not know, but one who definitely did was the American astronomer Professor David Peck Todd (1855-1939). Positioned on Mount Hamilton in California, his ‘solar photographic telescope’ was constructed by the optical firm Alvan Clark & Sons and enabled Todd to capture 147 wet-plate glass negatives. These images were rediscovered 120 years later, digitally copied and animated, and premiered before the International Astronomical Union in Sydney in July 2003. The conditions under which Todd operated were better, and the photographic plates superior, to Janssen’s expdition in 1874, and the resultant video is marvellously sharp. Once again, it needs to be pointed out that the images preceded motion picture projection by some years and were never seen in this way in 1882.

There is an excellent article on Janssen and his British imitators by Francoise Launay and Peter D. Hingley, ‘Jules Janssen’s “Revolver Photographique” and its British derivative, “The Janssen Slide”‘, originally published in Journal for the History of Astronomy vol. 36 pt. 1 no. 122 (2005).

From the same journal comes William Sheehan and Anthony Misch, ‘Ménage à trois: David Peck Todd, Mabel Loomis Todd, Austin Dickinson and the 1882 Transit of Venus‘ vol. 35 pt 2 no. 119 (2004), which includes the reanimation of Todd’s photographic plates and plenty on his interesting private life (his wife Mabel was responsible for the rediscovery of the poetry of Emily Dickinson).

After 1882, the next transit of Venus was in 2004. Tomorrow’s transit will be best viewed under cloudless skies around the Pacific Ocean, while in Europe we’ll see the transit already underway during sunrise on June 6th. There’s a guide on how and where to see it (don’t look at the sun with the naked eye, please) provided by The Guardian here. You can be certain of following it by watching one of the main live video streams on offer, a guide to which is provided here.

Everything you could possibly want to know about the transit of Venus is at www.transitofvenus.org, which rather wonderfully has a counter counting down the days until the 2117 transit. Just 38,538 days to go …

Follow

Get every new post delivered to your Inbox.

Join 300 other followers