Friday was another day when, because we didn’t get the predicted rain, I was able to enjoy some astrophotography: in this case, a conjunction of Venus and Mercury. (A conjunction is when two objects appear near each other in the sky.) Note that, even in the picture, you can see that Venus is a crescent. Like the Moon, Venus has phases, depending upon how much of its sunlit side we can see. In fact, it is even more of a crescent than it looks in the picture – only about 5.3% illuminated – as you can see in this neat animation. If you zoom in, you can see that Mercury is also not a circle – it is 67% illuminated. The two are different because they’re in different parts of their orbits relative to the Earth. Venus is close to passing between the Earth and the Sun, so we see very little of its sunlit side. The lines between Mercury and the Sun and the Earth and the Sun are almost perpendicular, so we see a much larger percentage of its sunlit side.
I have rarely seen Mercury, so this was a real treat. It’ll be visible for a few more weeks in the evening sky, so if the clouds stay away, I’ll have another look.
Camera Geek Info
- Canon EOS 60D in manual mode set at f/5.6, 1/30 second exposure, ISO 800
- Canon EF 70-300mm f/4-5.6L IS USM lens, set at 300 mm, manual focus