Astronomy Now Online

Venus transit widely observed
Posted: June 10, 2004


Sir Patrick Moore observed the transit of Venus from his home in Selsey in between reporting live for the BBC and recording a Sky at Night special. While others around him chose high-tech solutions to view the transit, Sir Patrick elected to use his 70-year-old 3-inch refractor to project the Sun's image onto a card.

Image credit: Astronomy Now.

For thousands of observers across the British Isles, the dawn of Tuesday, June 8th brought the kind of weather they had fervently wished for: clear, cloudless skies for the transit of Venus. Many keen amateur astronomers had taken the day off work to see the rare and beautiful sight of our sister planet gliding across the face of the Sun, an event last seen in 1882.

While most people saw the spectacle from home using binoculars or small telescopes equipped with solar filters, many gathered at special transit 'parties' like that at the historic Royal Observatory Greenwich in Greenwich Park, London. BBC presenter Adam Hart-Davis joined the crowds at Greenwich to bring results from British enthusiasts in Egypt and the village of Much Hoole in Lancashire at the home of Jeremiah Horrocks, who saw the transit of 1639.

BBC coverage extended to the home of Sir Patrick Moore in the coastal town of Selsey, West Sussex, where a veritable forest of telescopes stood trained on the Sun. Conditions there were excellent, and several observers chose to view the event in hydrogen alpha (H-α) light. This had never been done before, so no-one knew quite what to expect.


Renowned U.K. planetary imager Damian Peach was also stationed at Selsey, equipped with a Vixen 80mm apochromatic refractor, Baader full aperture solar filter and ToUcam Pro Web camera, with which he secured these images of the ingress and egress of Venus. Click on either montage for a larger view.

Image credit: Damian Peach / Dave Tyler.

One of the eagerly anticipated features was the so-called 'black drop', an effect seen when the disc of Venus is tangential to the Sun's limb and a droplet or ligament appears between them, making timings difficult. The black drop was famously evident during the transit of 1769 observed by Captain James Cook in Tahiti. While many did see (and photograph) the effect this time round, early reports suggest it didn't manifest itself in H-α light. Others report that with large aperture, high-contrast instruments it didn't appear at visual wavelengths either. Clearly, the phenomenon is still far from being explained and rival theories will be hotly debated in the weeks and months to come.

Another aspect of Venus observation met with a far greater consensus: the visibility of the Venusian atmosphere. Just after third contact, when the limb of Venus was exiting the disc of the Sun, many observers around the world reported (and again photographed) seeing a ring of light concentric with the edge of Venus on the portion of the planet's globe that was off the face of the Sun. This was clearly refraction of the Sun's light within the thick atmosphere of Venus. However, others claim to have seen it before second contact, but the vast majority of observations have still to be reported.


Renowned rock guitarist and music producer Brian May (now Dr Brian May) joined in the revelry at Sir Patrick Moore's home and proved he's also an accomplished observer. Here he uses his first home-made childhood Newtonian reflector to project an image of the Sun for Sky at Night transit special co-presenter, Chris Lintott.

Image credit: Astronomy Now.

While large groups of observers were intent on gathering valuable scientific data and timings, the six hour duration of the transit meant there was plenty of time to chat and reflect. For many groups, the event took on an air of celebration, and this was very evident at Sir Patrick's home and gardens in Selsey. Here astronomers both amateur and professional were able to mingle and reminisce, while legendary rock guitarist Brian May, now Dr Brian May, showed he was an equally skilled observer.

Even now, astronomers are looking forward to the next transit of June 6th, 2012. Unfortunately for U.K. astronomers, however, this transit will be largely over when the Sun rises on that day. Third contact will occur with the Sun just 6° above the east-northeast horizon at 5:38 a.m. BST for an observer at the centre of the British Isles.

For those seeking more information on the 2004 transit of Venus, a joint British Astronomical Association, Federation of Astronomical Societies, and Society for Popular Astronomy Web page has a gallery of observations received so far.