Mark that site!

By Steven van Roode

The scientific expeditions to observe transits of Venus of the eighteenth and nineteenth century brought astronomers to various distant and remote places. The accounts connected to these expeditions sometimes read as an adventure story. The last transit of Venus in June 2004 formed a catalyst for many initiatives to erect markers that would commemorate these expeditions. Now again, you can be part of marking astronomical history!

Marking historical sites related to the transit of Venus

A great example is the historical marker at Fort Sam Houston in San Antonio, Texas to commemorate the 1882 US Naval Observatory expedition led by Asaph Hall, which was erected in December 2004 on the initiative of Paul Maley. Paul travelled several times to San Antonio to pin down the observation places using the historical accounts of the observation and modern GPS. He and his team conducted an extensive search to attempt to relocate possible remnants of piers used for the USNO telescopes. Paul also worked with the staff of Fort Sam Houston Museum to construct a base marker which would acknowledge the importance of the transit observations by Asaph Hall and his team. Read Paul’s full story here.

The plaque commemorating the USNO expedition at Fort Sam Houston. (Photo by C. Reynolds)

Another fine example is the site of the observatory of Lord Lindsay at Belmont on Mauritius, where he observed the 1874 transit of Venus. After the site had been accidentally relocated when the administrator of Belmont noticed columns sticking up from the soil, the government, honouring the wish that “it would be well, in the interests of science, that the actual spot on which the observations were taken should be preserved”, cleared the site, revealed its foundations and designated it a national monument. On the occasion of the 2004 transit of Venus, thousands of people watched the celestial phenomenon from the very same place where Lindsay had seen the spectacle 130 years before!

Investigating, preserving and restoring historical sites

When astronomers arrived at a place, temporary observatories were set up: concrete or metal piers for the telescopes were firmly secured in the ground, prefabricated wooden observatory sheds erected and little huts built to live in. Upon their departure, most of the immovable parts were left untouched and these remnants of mainly nineteenth century expeditions still survive up to today, but often in a deplorable state.

Left: the iron frame of the observatory dome from the 1882 German expedition to South Georgia. (Photo by David Nicholls) Right: two transit piers of the 1874 British expedition to Kerguelen Island. (Photo courtesy of TAAF)

In 2006 and 2007 an international team of archaeologists investigated the site of Observatory Bay on Kerguelen Island, where in December 1874 a British expedition led by Stephen Perry observed the transit of Venus. Investigations like these often reveal the mundane details of daily life, not found in official publications or scientific records. Also at Observatory Bay the two piers for the transit instrument were found still in place: adjusted by later scientific missions and one broken in two pieces. Read the full story here.

A number of historical sites have already been marked, either by the astronomers themselves upon their leaving or much later by persons aware of their historical significance. The former aren’t always conspicuous, especially in remote places, as the following excerpt from Dallas Murphy’s Rounding the Horn shows. They’re looking for the monument left behind by the 1882 French Romanche expedition at Bahía Orange:

‘If you were a Frenchman, where would you put up your monument?’ Hamish wondered.
We split up. Some of us inspected the north shore of the cove, others poked around the concrete things, while Kate and Hamish took to the hills for an overview.
At the end of the beach, a near-vertical slab of rock dropped straight into the water, and on the otherwise black slab was a nearly square patch of white. To get to it, I’d have to edge along a boot-size, wave-washed ledge, an oddly inaccessible site for a monument… Hamish and Kate had spotted something on the opposite ridge. That made sense, the ridge overlooking the main part of Bahía Orange, that’s where you’d want your monument.

But many of the sites where astronomers observed the transit of Venus go unnoticed today. Sometimes we do not even know where certain stations were actually located. Like, for example, the site of the 1874 Italian expedition to Madhupur (Jharkhand, India), where Pietro Tacchini made outstanding spectroscopic observations of the transit. The official report only mentions a rented a bungalow in which grounds the instruments were set up, and a small map showing the placement of the instruments with respect to the bungalow. And that’s all. Wouldn’t it be great if the site of such a well-known expedition is relocated, investigated and marked?

Building 3D models

Marking sites can also be done virtually in Google Earth. There’s already a Google Earth file with all the stations listed on our ‘Past transits’ page. What’s still missing are 3D renderings of the observatories. By building 3D models of the observatories in Google Earth, people will have the opportunity to get an idea of the layout of the domes and cabins astronomers lived in for weeks, sometimes months, under difficult circumstances. These models can also offer a means to project the written accounts unto the factual surroundings, explore sightlines and examine the orientation of the buildings with respect to the heavens. A great tool to create 3D representations of the historical observatories is Google SketchUp. Pictures and physical descriptions of the observatories, especially of the nineteenth century, are abundant and can be found on this website.

Observing station of William Harkness in Hobart Town, Tasmania (1874).

For example, the nineteenth century American stations are well documented. In order to secure uniform observing conditions, the general layout was nearly identical to all expeditions. First, all standard wooden huts were erected during a training session in the grounds of the US naval Observatory in Washington. Then, these were taken apart, shipped to the various destinations and built up again by the crew. Despite the exceedingly different environments, all stations still looked very similar. Willy Koorts was even able to draw a scale drawing of a typical American observing post.

Scale drawing of a typical American station, by Willy Koorts.

Visualise the past and spend some time modelling the historical observatories in 3D!

Now it’s up to you!

Do you want to make a contribution to the history of astronomy? Wouldn’t it be great to have observations of the 2012 transit of Venus made from these historic sites? Join us in visiting and inventorying and possibly restoring or marking significant sites of past transit expeditions. Locating these sites helps to safeguard our astronomical heritage. The ‘Past transits’ section on this website may serve as a good starting point.

Contact us at: s.vanroode@transitofvenus.nl.