Toronto Transit Talks

Posted on May 17, 2012 by Steven van Roode

On Saturday 28 April 2012 a Transit of Venus 2012 Symposium was held at the University of Toronto. This Symposium provided scientific, historical, cultural, artistic, and educational perspectives for the 5 June 2012 transit of Venus, the last one visible during the 21st century. Videos of the talks given at the Symposium have now been released.
Jay Pasachoff’s 1-hour keynote address deals with the atmosphere of Venus and the black drop effect. In six other talks the search for exoplanets, educational opportunities, safe solar observing, instrumentation and the history of the transits of Venus are discussed.

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Origin of a famed photograph

Posted on May 16, 2012 by Steven van Roode

You’ve probably seen this picture before. It’s a photographic plate of the transit of Venus, taken by one of the eight 1882 American expeditions and it’s depicted in many books on the transit. Of the hundreds of dry collodion emulsion plates exposed by the American expeditions in 1882, only eleven survive today. And even of these eleven plates, no one can tell anymore from which station they originated. Or can they?

A couple of years ago I purchased an antique book from 1883, Transito de Venus por el Sol written by Luis Zegers. It gives a vivid description of the observations of the transit of Venus made from Chile by the French, Belgian, American and Chilean astronomers. The book also has an interesting frontispiece: an albumen photograph to scale of the transit of Venus, taken by the two photographers of the American party at Santiago.

The eleven photographs all have an inscription in the middle: ‘Fl 82’. The photograph from Chile has a similar writing: ‘Ch 82’. These letterings stem from the glass reticule plate which was placed in front of the sensitive plate and which had a grid etched on it, as well as some identification of the station it belonged to. That way, a grid to measure the pictures afterwards as well as an identification of the station became visible on each photograph that was taken.

The eight American expeditions were stationed at the US Naval Observatory (Washington), Cedar Keys (Florida), San Antonio (Texas), Cerro Roblero (New Mexico), Wellington (South Africa), Santa Cruz (Patagonia), Santiago (Chile) and Auckland (New Zealand). It’s great to have this photograph from Chile, because it makes clear that the two letters in de middle of the plate most probably refer to the station, leaving little room for doubt. If ‘Ch’ stands for Chile, than ‘Fl’ likely stands for Florida.

Comparing both pictures, it also is apparent that they were taken from two different hemispheres. On the picture taken from Santiago, Venus is on the lower half of the solar disk. Because on the southern hemisphere the Sun is seen ‘upside down’, the other picture should, in contrast, originate from the northern hemisphere.

This sounds very plausible, but still, additional research should show for certain. Each plate has a number, which corresponds to an entry in the photographer’s log, stating the time the picture was taken. It still needs to be checked if the positions of Venus on the Sun’s disk, as computed from the times listed in the log, correspond to the actual positions as measured on the photographic plates. The Cedar Keys’ log, however, is securely kept at the National Archives in Washington…

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Colonialism and the transits

Posted on May 15, 2012 by Randall Rosenfeld

One of the fortunate outcomes of transit research agendas was the publication of more science than just contact timings, the diameters of Venus and the Sun, and the distances between their limbs. Perhaps it is more enlightening to conceive of transit science as embracing more than the astronomy of the transit. How much more? It depended on who was observing, but the fact that many astronomers of the 18th century (such as William Wales on the shores of Hudson’s Bay, 1768-1769) had wider interests in natural history helped. Some expeditions included men whose primary interests were botanical, but botanists (e.g., Daniel Solander on Cook’s 1769 transit expedition) could and did do astronomy as well. The transit expeditions harvested data to enrich the fields of physics, hydrography, geography, geology, meteorology, botany, biology, and anthropology among others (the names of the disciplines and their divisions would have been different at the time).

Chappe D’Auteroche offers one of the best justifications for this catch-all sort of science, if any justification were needed: “Whoever considers the prodigious extent of a passage of several thousand leagues… and reflects that one unlucky moment, the least intervening cloud, might in one day defeat all our hopes [pinned on the transit], and render fruitless so much toil and expence [sic.], will not wonder at my taking these precautions, to draw other advantages from this voyage: that in case we should be so unfortunate as to fail in our main purpose, we might in some measure make amends to the learned world for this loss. Astronomy [in addition to the transit observations], geography, physic, and natural history, were the objects I proposed” (Chappe d’Auteroche, A Voyage to California, to Observe the Transit of Venus…, tr. anon [London: Edward and Charles Dilly, 1778], pp. 2-3). This made scientific, moral, and economic sense.

Particularly valuable for anthropology were the astronomers’ general narratives of their voyages. These are prime sources of information on what is now termed the “colonialism” of the expeditions.

It does have to be acknowledged that the word “colonialism” largely post-dates the period to which it is applied. This invites the question whether the link between the transit expeditions and colonialism is real, or a retrospective creation of politically charged academic discourse. The term may not have been familiar to astronomers and their patrons in the 18th and 19th centuries, but the concept certainly was. The Rev’d Thomas Hornsby, Savilian Professor of Astronomy at Oxford, wrote: “How far it may be an object of attention to a commercial nation to make a settlement in the great Pacific Ocean, or to send out some ships of force with the glorious and honourable view of discovering lands towards the South pole, is not my business to enquire. Such enterprizes, if speedily undertaken, might fortunately give an advantageous position to an astronomer, and add a lustre to this nation, already so eminently distinguished both in arts and arms” (On the Transit of Venus in 1769…, Philosophical Transactions 55 (1765), 326-344, at p. 344). John Winthrop affirmed that George II made the direct connection between the transit expeditions, the improvement of navigation, and British commerce, as did the Governor of Massachusetts when convincing Yankee merchants to part with their gold for science (John Winthrop, Relation of a Voyage from Boston to Newfoundland, for the Observation of the Transit of Venus, June 6, 1761 [Boston: Edes and Gill, 1761], pp. 7, 22-23).

The term is fraught, but taking it seriously can be fruitful, provided one can resist populating one’s colonial world with two-dimensional characters and straw men. Any assumption that white European scientists were to a man power-hungry materialists glad to be unwitting cogs in the imperial machinery, blindly exploiting the virtuous and powerless non-white, non-European peoples makes victims of everybody. Native people weren’t stupid; faced with what they were faced with, they were quite capable of exploiting colonial technologies and information sources to their advantage.

Continue reading →

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The right word on eye safety

Posted on May 14, 2012 by Tim Cole

Yes, I’ve written about this before. Now that public interest is ramping up, there are people giving very bad advice on how to observe the Sun. In the last few weeks, I’ve seen some old and dangerous ideas for do-it-yourself solar filters, along with a few new and dangerous ideas.

There are only two safe approaches to observing the Sun visually (i.e. without using cameras):

  • projection techniques — you look at a projected image of the Sun, but never at the Sun itself;
  • solar filters — you use filters that are certified to pass only safe levels and wavelengths of sunlight;

Homemade filters are risky. You have no way of knowing how effective they are at blocking excessive sunlight.  Don’t use any filter material that was not explicitly designed for visual solar observing. It’s really that simple. Don’t risk your eyes for the sake of saving a few dollars on a proper filter.

You might notice I’m not telling you how to observe the Sun safely. There’s a simple reason for that: you have absolutely no way of knowing if I know what I’m talking about. So what I recommend instead is that you learn about solar observing from someone you do trust.

Enjoy this marvelous Transit of Venus! Do it safely, and make it an event you’ll remember fondly.

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Return to the sources

Posted on May 13, 2012 by Randall Rosenfeld

The cry ad fontes, “to the sources”, was―is―a powerful call to revisit the fundamental data behind a statement, interpretation, or theory. The phrase has exerted a powerful effect in the learned world. Scholars have proclaimed it since at least the late 15th century, and their cry was not without social effect.

In the history of the transits, as in history in general, there are many statements handed from author to author, endowed with gospel-like truth by the repetition, and retold yet again. Fewer are the statements whose factual basis has been revisited. It is not easy to check everything, and mistakes are easy to make. I know, for I have made them.

The best known instance of a return to the sources of transit history is Simon Newcomb’s 1883 re-examination of Fr. Hell’s 1769 Vardø transit observation journal. For over a century Hell had been suspected of falsifying his data―claims which reached a climax with the publication of Carl Ludwig Littrow’s P. Hell’s Reise nach Wardoe bei Lapland und seine Beobachtungen des Vemus-Durchganges im Jahre 1769 (Wien: Carl Gerold, 1835). Newcomb went back to the source document, critically examined it, and was thereby able to exonerate Fr. Hell of Littrow’s charges of falsification. (Enough time has passed that this should probably be done again, by a team of codicologists and palaeographers fully informed of the recent methods of examination of “the book as artifact”).

Another instance concerns the portable observatories used in the British 1769 transit expeditions, such as those of William Wales and Joseph Dymond to Hudson’s Bay, or James Cook and Charles Green to Tahiti. These are illustrated in many modern accounts by a plate which was first published in William Wales and William Bayly, The Original Astronomical Observations, Made in the Course of a Voyage Towards the South Pole, in His Majesty’s Ships the Resolution and Adventure… (London: W. & A. Strahan, 1777), pl. II. One problem with the use of that plate to illustrate the transit observatories is that it postdates the transit campaigns. A more serious problem is revealed in Wales’ text: “The Observatory was contrived by my associate Mr. W. Bayley, and is undoubtedly one of the most convenient portable Observatories that has yet been made”. In other words, Mr. Bayly’s portable observatory is something new, an innovative piece of technology designed and made specifically for the astronomers on Cook’s “Second Voyage” of 1772-1775. An equally serious objection is that Wales and Dymond’s portable observatory was designed by the great civil engineer John Smeaton, FRS (1724-1792), and not by Bayly. According to Harry Woolf: “… the [Royal] Society was also informed of the Hudson’s Bay Company’s cooperation [for Wales and Dymond], which included the recommendations that the building intended for the observatory be prefabricated in England because of the shortage of proper wood in the region. A special octagonal building was then designed by Smeaton, Maskelyne [the Astronomer Royal], and Ashworth, the Greenwich carpenter. It included brass rings and rollers for a slotted roof…” (The Transits of Venus: A Study of Eighteenth-Century Science [Princeton, NJ: Princeton University Press, 1959], p. 165). Wood was clearly the major component of the 1769 portable observatories for the transit, yet it is clear from the 1777 description that the major component of Bayly’s portable observatory was canvas (viii-x). Canvas would have proved a remarkably poor choice in a sub-artic climate in which Wales recorded that he and Dymond regularly awoke in winter with their bedclothes frozen! It should also be noted that Bayly’s observatory was not “octagonal” in form.

To add to the difficulties, there does not appear to be extant any images showing the elevation of the 1769 portable observatories prepared for the transit. One of the buildings shown in the published image of Cook’s Fort Venus is sometimes identified as an image of the portable observatories (the centrally placed cylindrical structure with the flag pole). This identification is untenable, because the plan of Fort Venus identifies that building as “Mr. Banks’s tent”, with the observatory located a considerable distance behind, and with a much smaller octagonal ground plan.

We know that the portable observatories for the 1769 transit were chiefly of wood, that they were octagonal, had a “slotted” roof, and were designed by Smeaton. Is it possible to hazard a reconstruction? The answer is yes, and the tentative result is in the image at the top of this piece, informed by a later image of the roof of a Smeaton observatory.

This reconstruction will have to do, until such time as a rendering of the elevation of one of the 1769 portable observatories should come to light.

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Out of Diaries: 12 May 1769

Posted on May 12, 2012 by Andrea Wulf

Vardø was hidden under a thick blanket of white. A few weeks previously yet another storm had bucketed more snow on to the little island, but at least the long months of winter darkness had ended. Maximilian Hell and his assistant János Sajnovics had lived a secluded life since their arrival in mid-October 1768. Only once had letters from Copenhagen been delivered, but strangely they were better informed about the progress of some of their fellow astronomers than their colleagues in the scientific societies of London or Paris. On 12 May 1769, a Norwegian captain brought news that Jeremiah Dixon and William Bayley were preparing for the transit in Hammerfest and on the North Cape.

North Cape

Maskelyne and the Royal Society had decided that Bayley and Dixon should split once they reached the Arctic Circle to increase the chances of at least one successful observation. Dixon’s arrival in Hammerfest had caused much confusion. When the frigate anchored in Hammerfest, the inhabitants feared that the British had come with military intent, bringing ‘destruction into their country’ – but Dixon convinced them of his peaceful mission. On 12 May, as Hell and Sajnovics heard about their British colleagues, Dixon was bringing his instruments on shore. For the past days he had struggled to fix timbers to the ground which was, he wrote in his journal, ‘much frozen and rocky’.

Two days later, Hell received more news in Vardø when the crew from another ship told him that one of the Russian observers had died on Kildin, a small island north of the Kola peninsula in the Barents Sea – this was the astronomer Ochtenski – the first but not the last transit astronomer to die while chasing Venus.

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The transit and longitude

Posted on May 11, 2012 by Steven van Roode

In his new book, The Day the World Discovered the Sun, Mark Anderson follows three travelling scientists on their way to observe the 1769 transit of Venus. By observing the transit from far-flung places they sought to uncover one of the 18th-century’s greatest scientific mysteries: the dimensions of the solar system. Tracking the expeditions Jean-Baptiste Chappe d’Auteroche to Baja California, Father Maximilan Hell to Vardø Norway, and most famously, the journey of Captain Cook to the island of Tahiti, we find out how these journeys also helped to revolutionise navigation at sea. Especially, new methods of finding one’s longitude were tested. Basically, there were two solutions to the longitude problem: one mechanical, using clocks, and one astronomical, making use of the position of the moon with respect to surrounding stars. The working out of these solutions found their high point around the time of the 1761 and 1769 transits of Venus. In an IEEE Spectrum magazine’s podcast interview, Mark explains what role the 18th century transit expeditions played in the longitude problem.

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Interactive transit

Posted on May 10, 2012 by Randall Rosenfeld

What are we to make of the upcoming spectacle?

Many, particularly in the 17th and 18th centuries, spoke of transits of Venus in terms we reserve for what hangs on the walls of art galleries, flourishes in formal gardens, or reverberates from the rose of a lute. Jeremiah Horrocks was moved to state: ecce jam rarius spectaculum, nostroque seculo, non iterandum (“Now behold this rarest of spectacles, and in our age one not to be repeated!”). John Winthrop, the ‘Hollisian Professor of Mathematics and Natural Philosophy’ at Harvard College, wrote in 1761 that: “we had the high satisfaction of seeing that most agreeable Sight, VENUS ON THE SUN”, and in 1769 that “On account of their rarity alone… [transits of Venus] must afford an exquisite entertainment to an astronomical taste”. The Rev’d Dr. Nevil Maskelyne, the fifth Astronomer Royal, and a good friend to Caroline Herschel, wrote of the beauty to be seen when viewing the transit through a telescope in the 1769 Nautical Almanac. The Rev’d Dr. Edmund Halley himself, Maskelyne’s predecessor and the effective architect of the hunt for the solar parallax via the transit, famously wrote in 1691 that: hoc etenim spectaculum inter Astronomica longe nobilissimum (“This, in fact, is by far the noblest sight among astronomical sights”).

The noblest sight among astronomical sights.

Or is it?

A distinguished colleague of mine has likened the actual experience of watching Venus progress across the face of the Sun “to watching paint dry”. Nick Lomb reports that one 17-year-old visitor to Sydney Observatory for the 2004 transit, noticing the large crowd which lined up to witness the event, remarked to a local newspaper that: “It’s a pretty big turnout for a dot”. So, who’s right about the transit, Horrox, Halley, and Miss Herschel’s friend, or the unimpressed teenager and the jaded historian?

If truth be told, all of them are right. The reason for this lies in the nature of our relationship to the transit, that is, in our individual relationships to the transit. Put in the simplest of modern terms, the transit of Venus is an interactive event. The quality of your individual experience of the transit depends entirely on how you fashion that experience, before, during, and after June the 5th-6th.

Each of you chooses the tweets you follow, the apps you download, the photos you upload, the profiles you create and the friends you select, just as you curate the digital music and videos you wear on your person. Your social-media presence is created out of sources combined and recombined, drawn from hither and yon. This blog, and others like it, are the source stuff out of which you can design an informed real-time encounter with live science on June the 5th-6th. In the memory’s eye and ear each of us can mix our own images and sounds into a powerful, allusive, and alive commentary on the transit, as it happens, which we can share with others then, and afterwards.

There are worlds new to each of us to be perceived through this process. And you won’t know what they are till that sunset in early June.

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Chasing Venus

Posted on May 9, 2012 by Steven van Roode

On June 5 and 6 millions will watch a rare astronomical spectacle for the last time this century: the transit of Venus. With the event quickly approaching, we’re looking forward most of the time: choosing an observing site, searching for venues, experimenting with equipment, enthusing others – in short: making sure we won’t miss this astronomical spectacle, as we won’t see it again until 2117. But at the same time we ought to look back: to the astronomers in history who were so fortunate to enjoy the view of Venus against the solar disk. Our own observation on June 5 and 6 may benefit from their experiences. Knowing what astronomers of yesteryear went through to catch a glimpse of the transit of Venus may put our own view of the very same phenomenon into perspective: it places us in a line of humans privileged to see a transit, running from Jeremiah Horrocks to our own time.

Andrea Wulf’s new book Chasing Venus – The Race to Measure the Heavens gives us a lively insight into the transit of Venus enterprise in the 18th century. With a keen eye for detail she pictures the hazardous journeys of astronomers, sent out by their governments and scientific institutions to be part of what would become the first internationally coordinated astronomical campaign: the search for the distance to the Sun by measuring the 1761 and 1769 transits of Venus. If you want to be fully prepared for the transit next June, you should read this book! Next to the English edition (both UK and US), it’s being published in different other languages like German, Dutch, Portuguese, Italian, Japanese and Swedish.

Here’s Andrea herself, telling about her book:

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Star of China’s fortune

Posted on May 8, 2012 by Steven van Roode

On May 9 at 9:05 UT, astroid 139 Juewa will occult 12.2 magnitude star TYC 7446-00847-1. Juewa is a 157 km wide piece of rock orbiting the Sun in a highly eccentric orbit at a distance between 2.3 AU (perihelion) and 3.2 AU (aphelion). On earth, the occultation path extends roughly from Oklahoma, via Venezuela to the northern part of Brazil. All very interesting you might think, but why is this announcement on a blog entirely devoted to the transit of Venus?

Juewa was discovered on October 10, 1874 by James Watson during his stay in Beijing as chief astronomer of the American expedition to observe the transit of Venus. At that time astroids had only entered the celestial stage a little while back and Watson’s discovery excited much interest. This is Watson’s own account of the find:

On the night of the 10th of October, while observing in the constellation Psices, with the 5-inch equatorial, I came across a star of the eleventh magnitude in a region of the heavens with which I was very familiar, and where I had not hitherto seen any such star. Subsequent observations the same night by means of a micrometer, extemporized for the purpose, showed that the star was slowly moving retrograding, and that it was a new member of the group of planets between Mars and Jupiter. The discovery was duly announced to astronomers in other lands, and it became also speedily known in Peking. Some mandarins of high rank came to our station to see the stranger with their own eyes, and upon observing the change of configuration with neighboring stars upon two successive nights, they gave free expression to their astonishment and delight.

And what about the name? Even by then it was custom that the discoverer of a new planet had the honour to give it a name.

This being the first planet discovered in China, I requested Prince Kung, regent of the Empire, to give it a suitable name. In due time, a mandarin of high rank brought to me the document containing the name by which the planet should be known, coupled with a request–communicated verbally–that I would not publish the name in China until the astronomical board had communicated to the Emperor an account of the discovery and the name which had been given to the planet. This request was of course promptly acceded to; and I afterwards learned upon inquiry that if the knowledge had come to the Emperor otherwise than through the astronomical board, organized specially for his guidance in celestial matters, some of these ministers would have been disgraced.

Prince Kung’s choice was 瑞華星, Jue-wa-sing, which means “Star of China’s Fortune”. Tomorrow’s occultation is a great opportunity to gaze at one of the fruits of the transit of Venus expeditions. For more detailed information on the occultation, visit Steve Preston’s website. In order to see what to expect, take a look at the video, showing the occultation of 10.1 magnitude star UCAC2 17551271 by Juewa on September 26, 2007:

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