Sparking a revolution

Posted on April 21, 2012 by Steven van Roode

Ahead of the release of her new book Chasing Venus: The Race to Measure the Heavens, Andrea Wulf wrote an article for the Wall Street Journal today, explaining the revolutionary effect of the transit of Venus enterprise on the development of science in the eighteenth century. The recording of the 1761 and 1769 transits of Venus could help answering the pressing question about the size of the solar system. Andrea aptly states that “this endeavor would only work if scientists combined the observations from viewing stations in the Northern and Southern hemispheres. The calculations would be valid only if the astronomers traveled to far-flung corners of the world and then shared their results.”

And thus we are presented with the two challenges of the eighteenth century transit expeditions: getting otherwise home-bound astronomers to places far away in time for the transit, and sharing the results afterwards between countries that were at war with each other most of the time. In her book Andrea quotes Joseph Banks, who travelled with James Cook on the Endeavour to observe the 1769 transit of Venus from Tahiti and who became an advocate of global cooperation between scientific communities when president of the Royal Society:

‘The science of two Nations may be at peace’, he said, ‘while their Politics are at war’ – and it was this peace of the sciences that proved to be of vital significance for the advancement of knowledge.

You can read the entire Wall Street Journal article by Andrea here and here.

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Hawaiian transit in the 1800′s

Posted on April 21, 2012 by Steven van Roode

Here is a new video by the Sun-Earth Day team about the transit of Venus, focussing this time on the nineteenth century transits of Venus. Special attention goes to the British expedition that observed the 1874 transit from Hawaii, but during the video you will also see pictures of expeditions at Eden and Kerguelen Island. If you didn’t see the first part of this video, you can watch it over here.

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Top sites to watch the transit

Posted on April 19, 2012 by Steven van Roode

In only seven weeks time the last transit of Venus of this century will be over. Are you still looking for a unique place to watch the transit? Here’s our top three! From each location you can see the entire transit, and they all have a link with history.

Point Venus, Tahiti
Tahiti is probably the best known historical site where the transit of Venus has been observed. At Point Venus, James Cook erected a fortified enclosure where he had his improvised observatory. The scene made it to covers of astronomical year books and even stamps. Any contemporary relics of the fort or the observatory are now gone, but there’s still a monument that commemorates the observation by Cook. On June 5 there will be a lot of people gathering at Point Venus to celebrate the transit through different initiatives related to historical, multicultural and scientific dimensions. Read more…

Vardø, Norway
In 1769 two Jesuit priest travelled all the way from Vienna to the north of Europe to observe the transit of Venus. They built a wooden observatory they had to use for months because they not only had to observe the transit, but make other astronomical observations as well to establish the geographical location of the place. After their successful observation of the transit, they sang a Te Deum in gratitude. Today, a plaque commemorates the stay of Maximillian Hell and Johann Sajnovics in Vardø. Next June, there will be a Venus Festival with lectures, cultural events and educational activities. And you will be able to see the transit of Venus on the midnight sun, just like the 1769 observers! Read more…

Sydney, Australia
In the nineteenth century, Sydney Observatory was the nerve centre of the Australian transit of Venus observations. From here Henry Chamberlain Russell organised a number of expeditions in New South Wales. Good weather provided for some interesting observations in 1874, especially of Venus’ atmosphere, but 1882 only showed clouds in Sydney on transit day. This year there will be several viewing sessions at the observatory. These sessions to view the transit of Venus at Sydney Observatory are currently booked out. However, if the weather forecast is for a clear sky, they may release further tickets in the days before the transit. Read more…

There are, of course, many other privileged sites from where you can see the entire transit. Hawaii, Japan and China are also ideal locations with a historical cachet. Did you already made plans to go somewhere? Let us know on our Facebook page.

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Cook’s three voyages

Posted on April 17, 2012 by Nick Lomb

A chart of the three voyages of James Cook. Red indicates the first voyage, green the second and blue the third. Courtesy Jon Platek and Wikimedia Commons

A reviewer of my book Transit of Venus: 1631 to the present in the April 2012 issue of the Bulletin of The Pacific Circle queries my reference to Cook’s first voyage (1768-71) as his ‘most famous’. The reviewer, who has strong links to Hawaii, suggests that it could have been his last – ‘the voyage that led him to the [European] discovery of Australia?’

As an astronomer and as an Australian I plead guilty of bias towards the first voyage as it was on that voyage that Cook observed the transit of Venus and on his return voyage his ship became the first European one to reach the east coast of Australia. However, I do realise that the view from Hawaii could be very different.

Accordingly, let us have a quick look at the three voyages and their achievements.

First voyage (1768-71)

We have already looked at a number of aspects of Cook’s first voyage such what telescope was used to observe the transit, why Cook sailed to Tahiti and how he navigated there. Here we will briefly summarise the voyage. Departing England in July 1768, Lieutenant James Cook in charge of HM Bark Endeavour sailed to Tahiti. Endeavour reached the island after a voyage of eight months during which none of its crew had succumbed to the disease scurvy, which was most unusual for the times.

At Tahiti Cook and his astronomer Charles Green observed the transit more successfully than they had realised. After the transit Cook followed his orders to search for the non-existent Unknown Southern Land until reaching New Zealand. There he spent six months charting the coast before departing for the east coast of the land known as New Holland. He followed the east coast towards the north charting as he went and claimed possession of the country on behalf of the British Crown.

Second Voyage (1772-75)
The aim of this voyage was to search once again for the Unknown Southern Land. A secondary aim was to test out navigation using chronometers, clocks that can function in spite of the motion of a ship and the great variation of temperature to be expected. On board the Resolution he had K1, a copy of Harrison’s prize-winning chronometer H4 and Arnold No 3 while the second ship on the voyage Adventure had two Arnold chronometers. Of the two used by Cook K1 kept excellent time so that Cook wrote, ‘Mr Kendal’s Watch has exceeded the expectations of its most Zealous advocate’, but the Arnold did poorly.

During the voyage Cook sailed further south than any explorer had before, but did not find Antarctica as ice and weather conditions blocked his way. During his exhaustive search of the Pacific he found or visited a number of islands such as Easter Island, the Tongan Group, New Caledonia and South Georgia.

Third voyage (1776-1780)

On this his final voyage, Cook was trying to find a route from the Pacific to the Atlantic round the top of North America. He was again on board the Resolution while the accompanying ship this time was the Discovery.

After observing an eclipse of the Sun from an island Cook named Christmas Island, Cook and his crew became the first Europeans to find the Hawaiian Islands. They made a short stop for water and went on with searching for the North West Passage. Not meeting with success, the ships and the crews needed rest so Cook sailed towards the Hawaiian Islands, landing at Kealakekua Bay on the Big Island of Hawaii. At first all went well, but later after a departure and an emergency return for repairs disaster struck and Cook was killed by the islanders on 14 February 1779.

Assessment

On his first voyage Cook solved the problem of scurvy that had plagued seamen on long voyages, observed the transit of Venus, charted New Zealand and the east coast of Australia. To me, and I may be showing my biases here, this voyage still seems to me to be the most important, successful and famous of the three. However, I do understand that someone from Hawaii would vote for the last, sad, voyage instead.

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A stroll through Aiken’s woods

Posted on April 16, 2012 by Steven van Roode

In 1882 a German expedition was stationed at Aiken, South Carolina, to observe the transit of Venus on December 6 of that year. Headed by Julius Franz, the team set up an observatory typical of the German transit of Venus stations: two drum shaped domes for the telescopes, and a rectangular housing for the transit telescopes. Relics of this observatory are still there to see: the iron frame of one of the domes is now in the grounds of the Aiken County Historical Museum, while an inscribed stone slab that served as a solid base for one of the telescopes remains at its original location in the backyard of a private residence on Edgefield Street.

Advertised as a ‘health resort’, Aiken wasn’t a quiet town at all in 1882, and the German expedition was introduced to some alarming incidents, sometimes of a racial character. Upon their arrival they found themselves in the heat of an election: men with revolvers in their hands went through the streets on horses looking for the candidate of the opposite party who had held a speech earlier; their hotel was barricaded because of the incident. Another time, a large crowd was about to storm the house of a black man that had been accused of assaulting a white women. Policemen had to protect the man when he was transported to jail.

One day, one of the German astronomers, Hermann Kobold (pictured on the far right in the photograph) went with his fellow astronomer Adolf Marcuse for a walk through the woods to collect plants. With the incidents still fresh on their retinas, they were terrified when they entered upon a group of Aiken residents. Kobold wrote in his memoires:

Aiken is located between large forests. I was still collecting plants for my herbarium and wanted to learn about the flora of these forests. So I decided to take a walk in the woods with my fellow traveller Marcuse on a Sunday afternoon. A path lead into the woods. We had already entered a few hundred yards into the woods, when we saw a couple of black men coming in our direction. When they saw us, they stopped and talked among themselves and with their apparently leader, a big guy with a straw hat, collar and cuffs. My companion had become anxious and wanted to turn back, but I thought this is was already too late and it was better to walk on. That’s what we did and the guys let us pass without difficulty. As we recounted our experience at dinner, we were told it was very foolish of us to have gone into the woods without protection; it could easily have gone wrong for us. Also at our observatory, we had to place a guard both day and night.

Accounts like these add the necessary couleur locale to the scientific reports of the expeditions, so we may appreciate the circumstances under which they had to perform their astronomical work.

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Chappe in Baja California

Posted on April 14, 2012 by Chuck Bueter

Plaque at Cabo

You have to respect Jean Baptiste Chappe d’Auteroche and his party that went to Baja California to observe the 1769 transit of Venus. Imagine the travails of their multi-leg journey:

  • 11 weeks of tedium at sea, tossed from France to Mexico in a frail boat that was “the sport of the smallest wave;”
  • 7 weeks traversing Mexico on “sorry mules, and in bad weather and detestable roads;”
  • 4 weeks trying to get across the Sea of Cortez in “so little wind, and that little was so often interrupted with calms…we then began to despair of getting to California in time for the observation, which would have been a most cruel disappointment.”

Eventually they reached the Baja peninsula near the Tropic of Cancer with only two weeks to spare. Chappe chose the challenging option to land in the surf at San Jose del Cabo rather than risk further delays trying to sail to a more genteel beach. Better to “lose a poor little pitiful vessel, than the fruits of so important an expedition as ours…Besides, we were not the first that had landed at the Mission of San-Joseph.” Indeed, a mission had been established there in 1730 by Jesuit priests Sebastian Sisneaga and later Nicolas Tamaral.

Chappe and the Spanish astronomers Vicente de Doz and Don Salvador Medina who accompanied him eventually set up their equipment at a nearby barn whose roof they partially cut away. Within two days of their successful observation, though, most of the team became afflicted by an “epidemical distemper” that wiped out one third of the local population. The video UNESCO-17-Science and Enlightenment: The Transit of Venus includes a reenactment of their expedition.

Today, San Jose del Cabo is a thriving tourist destination. The mission that existed when Chappe and his team arrived has relocated a few times, with the current site being inland from the beach. The church is a clean, attractive structure flanked by two towers with a welcoming plaza around it.

A short walk away is the Casa de la Cultura, a curious place built around 1974 with a theater and museum space, though from recent conversations with passers-by I sense the museum does not have any contents and exists more in name than in reality. The building is distinguished by a fun, colorful mural on the facade that celebrates the arts.

Tucked within the Casa de la Cultura, though, is a genuine treat for transit of Venus enthusiasts. There is one of the many markers from past transit of Venus expeditions that are getting attention from a growing audience by virtue of their connection to the June 5-6, 2012, celestial alignment.

To find the plaque commemorating the 1769 expedition, enter through the front double doors into a small foyer and it’s ahead on the wall. In a comical twist, when there is an audience attending the theater who would be potential viewers of the marker, the plaque is covered by the large wooden door that slides right and obscures the full text. If you vacation (or reside) near San Jose del Cabo, take a side trip to visit the well-deserved acknowledgment of this intrepid scientific party.

Chappe summed up the satisfaction of being “conquerors over the most formidable elements…A secret pride then rises in his mind; he says within himself, ‘If man, as an individual, is but a speck, an atom in this vast universe, he is, by his genius and his daring spirit, worthy to embrace its whole extent, and to penetrate into the wonders it contains.’”

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Aiming at the Sun

Posted on April 12, 2012 by Tim Cole

Shadow cast by a solar telescope Finding the Sun with a properly filtered telescope doesn’t have to be difficult. The “Minimum Shadow Method” is reliable and easy to learn. The key to this simple technique is to pay attention to the size and shape of the telescope’s shadow.

Start by roughly aligning the telescope with the Sun (you remembered to check the solar filter, right?). Most likely, the shadow will look a lot like the one in the photo on the left. The elongated shape of the telescope tube’s shadow is a clue that there’s a lot of azimuth error. Rotate the telescope mount to shorten the telescope’s long, boxy shadow.

An oval-shaped shadow hints at an error in elevation. Move the telescope tube up or down to get a roughly circular shadow. The photo on the right shows the shadow when the telescope was aimed directly toward the Sun.

Once you’re satisfied with the shadow’s size and shape, remember that you’re at least close to the Sun. Use a low-power eyepiece and make small adjustments until the Sun appears in your field of view.

It’s easiest to use the Minimum Shadow Method when you have a smooth horizontal surface available. With practice, you’ll find you can work with a shadow cast on a wall or even a curved surface such as a large planter. Even if you decide to use a commercial or home-made Sun finder, you’ll find this method comes in handy for aligning the finder and the telescope.

Telescope's oblong shadow Telescope's small shadow
Left: The shadow of a misaligned telescope. Right: An aligned telescope’s shadow.

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What telescope did Cook use?

Posted on April 11, 2012 by Nick Lomb

A brass reflecting telescope similar in appearance and optical design to those used by Captain Cook and his astronomer Charles Green at Tahiti to observe the transit of Venus on 3 June 1769. Courtesy Powerhouse Museum

I have received the following letter from Stuart:

I recently purchased and have just finished reading your book, Transit of Venus 1631 to the Present. I would like to pass on my appreciation for the obvious effort that went into publishing a book of such high quality.

I do have a question if you have some time. On page 74 of your book, the James Short Telescope is noted as a reflector. It looks like a refractor to me.

What is the optical design of this scope, reflector, sct or refractor?

Stuart is right that the James Short telescope illustrated in the Transit of Venus book, or the almost identical Dudley Adams telescope shown to the left, do resemble a refracting or lens telescope in that the eyepiece is at the bottom end of the telescope just as in a refractor. This is in contrast to the well-known Newtonian design of a mirror telescope where the viewing point is near the top of the tube at the side.
 

James Short’s telescopes had a Gregorian design. This design was due to a Scottish mathematician James Gregory who suggested a design for a reflecting telescope in 1663, but was unable to build it himself or get someone else to build it for him. Hence the honour of building the first reflecting telescope went five years later to Isaac Newton, who presented a working model of his own design to the Royal Society in 1668.

A cross-sectional drawing showing light rays inside a Gregorian telescope. Courtesy Wikimedia Commons and ArtMechanic

The Gregorian design due to James Gregory is based on two mirrors: a primary mirror of parabolic shape and a secondary mirror of ellipsoid shape placed after the focus point of the primary to reflect the light back down the tube. There it passes through a small hole at the centre of the primary mirror and is then examined through an eyepiece.

James Gregory has a connection with the transit of Venus in addition to the fact that James Cook used a telescope of his design. In the same 1663 book Optica Promota that Gregory suggests his new reflecting telescope design he also makes the comment in a Scholium to Proposition 87 that

Hoc Problema pulcherrimum habet usum, sed forsan laboriosum, in observationibus Veneris, vel Mercurii particulam Solis obscurantis : ex talibus enim solis parallexis investigari poterit.

Or in English

This prettiest of problems has a use, but perhaps a very laborious one, in the observations of Venus or Mercury obscuring a little part of the sun : indeed from such the parallax of the sun will be able to be investigated. (Translated by Ian Bruce)

Thus James Gregory did suggest using transits of Venus for solving the problem of the distance of the Sun long before Edmond Halley did in 1716. Halley receives credit as, unlike Gregory, he provided a practical method for making the measurement and not just a hint that transits could be used for the purpose.

James Short was born in Edinburgh, Scotland, in 1710, and was orphaned at age 10. Encouraged by a professor of mathematics after graduating from Edinburgh University, Short began making reflecting telescopes. The most difficult part in making telescopes was to grind the mirrors of speculum metal and he became much more successful than his contemporaries in giving these mirrors the required parabolic shape. His fame spread quickly and by 1736 he was summoned to London to teach mathematics to William, Duke of Cumberland, who was the younger son of the King and was later to be known as ‘Butcher Cumberland’ after the Battle of Culloden in Scotland. Within two years Short had moved permanently to London, where his telescopes commanded twice the price of those of his competitors.

Short observed the 1761 transit of Venus from London using one of his own telescopes and later as a Fellow of the Royal Society he made a detailed analysis of the various observations by British observers of that transit. Sadly he died in 1768 before the following transit that was observed by James Cook among many others around the globe. It is believed that he completed 1370 telescopes in his lifetime.

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The transit in a nutshell

Posted on April 10, 2012 by Steven van Roode

Here’s a great new video from Lab, Camera, Action! Written and presented by Andrew Steele, it delves into the mechanics of the transits of Venus on June 5 and 6.

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Transit, Talks and Chasing Venus

Posted on April 8, 2012 by Andrea Wulf

I’m going to briefly (for one post) step back from ‘Out of Diaries’ to post something about the near future.

I think I got one of the best gigs on the planet for the transit of Venus… I’m going to watch the transit at the Kitt Peak National Observatory in Arizona. Admittedly I won’t be able to see the entire transit but the predictions for sunshine are pretty amazing there – something like 93%.

Even better I’m going to give a talk about my forthcoming book “Chasing Venus. The Race to Measure the Heavens” during the transit. I’m going to watch the beginning of Venus’s march across the sun, and then I’ll make a dash for the Visitors Centre to give a 45min talk… and then I’ll dash back to the telescopes.

So, come and join me. The Kitt Peak National Observatory team has put together an amazing programme of transit activities which includes several solar telescopes and a live projection of the transit with their Heliostat. The tickets also included a full after–dark observing session.

It’ll be on 5 June (since it’s in Arizona) and the activities start at 2pm (about an hour before the transit).

Click here for a list of all my talks.

Click here for info about “Chasing Venus”.

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