Transit of Venus 2012

The second and last transit of Venus in the 21st century required a little more effort to observe (in terms of travel) than that of 2004. While the first was visible from my home in Cheshire, the second was only visible in its entirety from the mid-Pacific.

I therefore joined a 23-day tour that headed first for the western US to visit several observatories and observe an annular eclipse of the Sun, before heading on to Hawaii for the transit.

Big Island, Hawaii,   5th June 2012

The above montage spans a period of around 7 hours. Four of us from the tour decided to form a splinter group and observe the transit from a beach on the west coast of Big Island. While the rest of the group went up to the Mauna Kea visitor center and viewed the transit from the car park there, we headed for Spencer Beach Park near Kewaihae.

Although Mauna Kea was almost guaranteed to be cloud-free, the final part of the transit would not be visible from there as the Sun dropped below the neighbouring mountains. Our beach site guaranteed a view of the entire transit, which was due to end just 20 minutes before sunset, but we had to take our chances with the clouds.

In the event, we saw the start of the transit clearly. I was intending to take an image every 20 minutes, but clouds did intervene at times, as can be seen in some of the images.

Venus is very difficult to see in the first image at this scale, but with some magnification (and perhaps imagination) the little bump of first contact is there.

The transit in progress

The transit began exactly on time and for those of us who had seen transits of Mercury, the difference in size of Venus’ disk was immediately obvious. Not only is Venus about 3 times the size of Mercury, but it is only about half as far away during a transit, so its black disk appears about 6 times larger on the face of the Sun. Venus also takes longer to cross the Sun’s disk than Mercury as its orbital speed is slower due to its greater distance from the Sun.

The distinctive triangle of sunspots was visible even in low-magnification equipment and became a memorable feature of this transit. 

This image and all those in the montage above were taken through a Meade ED5000 80mm f/6 refractor using a Nikon D700 DSLR. Exposure was 1/4000 second at f/6.3 and ISO-200 through Baader Astrosolar safety film.

Spencer Beach Park, Big Island, Hawaii

Observing the 7-hour transit from a beachside location in the blazing Hawaiian sun has its compensations. We managed to go swimming in the sea between taking images!

The above image shows the bay – our observing site (below) was much closer to the beach than this and shows some intrepid observers.