A photo of Mercury at its maximum elongation

About now, Mercury is close to its maximum elongation.

This means that, viewed from Earth, it is as far from the glare of the Sun as it ever gets. This is our best opportunity to view the planet.

My house is on a hillside facing the west. I look out over a freeway and the Yarra, and I have a good view to the horizon from south-west to north-west. Unfortunately, I can only see it through a double glazed window, so my images weren't going to be great.

But the view wasn't the problem. I have to confess here that I'm not the world's keenest planetary astronomer. When I saw something, I didn't really know how I was going to be sure that it was Mercury. After all, it was going to be a dot, at best.

You see, Stellarium was telling me that Venus was going to be nearby, separated by about five degrees. Venus would be brighter, lower, and to the left of Mercury.

If I saw both planets, it would be easy. But what if I saw only one? How could I be sure it was Mercury, and Venus had disappeared into the trees? Why couldn't it be Venus, and Mercury had been lost in the glare?

I sat in the window and worried. This is something I do.

Obsessively, I scanned the sky low to the north-west with my binoculars. I'd set the camera up in preparation and I was beginning to wonder if I shouldn't have bothered.

Around 5:40 I spotted something near a freeway light. It was quite bright, and I was surprised I hadn't spotted it already. I scanned up and down, searching for a second planet. I saw nothing, but took a photo anyway.

I watched as the planet slid lower and to the left. While it approached the horizon I did some back-of-the-envelope calculations.

Venus would set at around 6:02. Mercury would set shortly afterwards at 6:20.

At about 5:55, the planet moved into the trees. If Venus set at 6:02, it was now clear that this is what I'd been watching.

I waited, and presently I noticed a dimmer light above and to the right of where Venus had disappeared. This one couldn't have been anything other than Mercury.

As a plane approached, I reached for the camera. From that point, it was less than 15 minutes before Mercury slipped into the trees on the horizon. The sky still wasn't dark.