I haven’t written about any astronomical stuff for a while, but today was a special day — the 2012 Transit of Venus. A transit is just like an eclipse, but with a visibly smaller object moving in front of a large one; in this case, Venus moved across the face of the Sun, as viewed from Earth. These transits are rare — the next isn’t until 2117 — so I spent the morning at a special viewing event at the Melbourne Planetarium.
There were some clouds around early in the morning, but by the start of the transit at about 8:16, all was clear. The Planetarium had a great setup: a couple of small solar telescopes, which gave a great view of the whole Sun with some surface detail, and a couple of larger telescopes with heavy solar filters on them, which had more zoomed-in views. There was also a telescope set up to project the Sun’s light on to a projection screen.
After the actual viewing, there was a planetarium show explaining the mechanics of the transit, and discussing its historical importance; there’s some more detail on Wikipedia, but suffice it to say that observations of the transit were a big deal, and the 1769 transit in particular saw expeditions to all corners of the globe to get measurements. By the time the show was done, clouds had rolled over, and it looked like they were there to stay, but I hoped there’d be some breaks later in the day so I could make some observations from home.
I hadn’t intended to try observing the transit at home, but after seeing it at the Planetarium, I was ready to give it a go. I took a simple approach: I strapped my binoculars to a tripod, pointed the big end toward the Sun, and pointed the eyepiece toward a piece of paper set up as a makeshift projection screen. It was very rudimentary, but it worked! I attached some extra paper to the binoculars to act as a shade, making sure that the projection screen was in shadow to give the best possible image.
A simple projection setup for solar observation, using binoculars
I used my DSLR to get some photos of the projected image, too. The images aren’t super-sharp, but you can definitely see Venus, and even a couple of faint sunspots in one of the images:
A little bit before the end of the transit, with Venus still within the Sun's disc
Right near the end of the transit, Venus looks like a tiny indent in the side of the Sun
I had trouble with the clouds on-and-off at home, and they rolled over after that last shot and stayed for a while; by the time they cleared, Venus was long gone.
It was definitely worth the effort of setting up at home, and it was surprisingly easy to do. After observing this transit, I’m definitely keen to look at some other solar events — a solar eclipse would be great! I don’t know when the next solar eclipse is due, but whenever it is, I’ll be ready.