Monday, December 01, 2008

When I got home tonight about 5pm, I noticed the New Moon with Jupiter about 2 degrees away. I'd been expecting the Moon to be near Jupiter and Venus when it reappeared this month, and was impressed by how close it was to Jupiter.

But I was puzzled by the fact that I couldn't see Venus anywhere. I assumed it was behind a cloud or the houses, and went up to the end of the garden anyway to see how the Moon and Jupiter looked in binoculars.

Leaning against the shed I had a good look at the Moon with Earthshine, and tried to make an accurate guess at the distance to Jupiter - about 4 Moon widths or 2 degrees.

Then I inspected the craters on the lower limb of the Moon, which were in sharp relief because of the angle of the sunlight. Suddenly my attention was caught by a bright spot at about 4 o'clock on the edge of the Moon. 'Hmm, ' I thought, that'll be the side wall of a big crater catching the sunlight. Impressive.'

The spot got brighter and brighter until I was reminded of pictures of the 'diamond ring' effect during solar eclipses. And then (about 5.20pm) I realised that the Moon was actually moving clear of the spot, which of course was the missing Venus appearing from behind the Moon.

All unawares I'd been watching a lunar occultation of Venus, which I'd had no idea would be happening. One of the most beautiful and impressive astronomical sights I've seen.

I've had help many times from the library angel, but it's not so often that I'm blessed by assistance from Urania, the muse of astronomy.