1874 transit of Venus

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The transit as seen from Japan by Pierre Janssen
Map showing the visibility of the 1874 transit of Venus

The 1874 transit of Venus, which took place on 9 December 1874 (01:49 to 06:26 UTC),

the second transit occurring eight years later in 1882. The previous pair of transits had taken place in 1761 and 1769, and the next pair would not take place until 2004 and 2012.[n 2]
As with previous transits, the 1874 transit would provide an opportunity for improved measurements and observations. Numerous expeditions were planned and sent out to observe the transit from locations around the globe, with several countries setting up official committees to organise the planning.

Expeditions

French expeditions

There were six official French expeditions. One

Saigon in Vietnam.[2]

British expeditions

There were five official British expeditions or observation sites. One

Kerguelen Archipelago in the far southern reaches of the Indian Ocean, and Rodrigues, an island further north in the Indian Ocean, near Mauritius. A fourth expedition went to a site near Cairo in Egypt, and the fifth travelled to a site near Christchurch (now Burnham Military Camp) in New Zealand. Several of the expeditions included auxiliary observation stations that were constructed in addition to the main observation sites.[3]

American expeditions

In the

Crozet Island, but was unable to land there and instead made observations from Tasmania.[3]
These expeditions obtained 350 photographic plates for the 1874 transit.

Observations

The transit was observed from many observatories, including the

Goulburn in Australia.[3]

Italian astronomer Pietro Tacchini led an expedition to Muddapur, India. Other locations in India from where the transit was observed included Roorkee,[3] and Visakhapatnam.[3] The German astronomer Hugo von Seeliger directed an expedition that travelled to the Auckland Islands (subantarctic New Zealand islands).[3] German astronomers also travelled to Isfahan in Persia, and to Kerguelen.[3] The Dutch astronomer Jean Abraham Chrétien Oudemans made observations from Réunion, and observations were also made from various points in the Dutch East Indies.[3] Austrian astronomers made observations from Jassy, in what is now Romania.[3] The Russian astronomer Otto Wilhelm von Struve organised expeditions to make observations in eastern Asia, the Caucasus, Persia and Egypt. Two Mexican expeditions travelled to Yokohama in Japan.

There were also several individuals that journeyed to various locations to observe the transit, or funded private expeditions.

Beechworth, Victoria, in Australia.[3]

Not all the observers were able to make measurements, either due to adverse weather conditions, or problems with the equipment used. Many observers, particularly those on the official expeditions, used the new technique of photoheliography, intending to use the photographic plates to make precise measurements. However, the results of using this new technique were poor, and several expeditions were unable to produce publishable results or improve on existing values for the astronomical unit (AU). In addition to this, observations made of Mars were producing more accurate results for calculating the value of the AU than could be obtained during a transit of Venus.

See also

Notes

  1. ^ The timings given here are the geocentric circumstances, as viewed from the centre of the Earth.[1] The exact timings of a transit vary by a few minutes from these timings depending on the exact location it is viewed from on the surface of the Earth. It is these variations, due to parallax, that allow measurements of the timings to be used to calculate a value for the astronomical unit.
  2. Transit of Venus, 2012
    .

References

  1. ^ a b "1874 December 9th Transit of Venus". Transits of Venus. HM Nautical Almanac Office. Archived from the original on 25 January 2017. Retrieved 15 June 2012.
  2. ^ "Transit of Venus – 19th Century". Melbourne Observatory. Archived from the original on 27 April 2012. Retrieved 15 June 2012.
  3. ^ a b c d e f g h i j k l m van Roode, Steven. "1874 December 9". transitofvenus.nl. Archived from the original on 25 June 2012. Retrieved 15 June 2012.

External links

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Contemporary published accounts