At the u3a Stargazing session on Monday, we started talking about Asterisms. Beyond knowing they were something to do with stellar arrangements, and didn’t fully understand what an Asterism was. I didn’t know that I had been looking at them most of my life.
There are constellations that I have known for a very long time. One of them is Orion. I know the constellation (although I’m not very confident about the bow). I know two of the main stars, Betelgeuse (ask 10 people how to pronounce it, you are likely to get more than one different response) and Rigel. I know where the other stars that make up the body. One of the most obvious characteristics of Orion is his belt, the three stars across the centre of the body. What I didn’t know was that the belt is an asterism. It’s like an unofficial constellation within the official constellation.
I’ve found it very easy to forget that the Greater and Lesser Bears are not just the bigger and smaller ploughs. Both of these are asterisms.
The point of all of this is what came out of the Stargazing session. Antony suggested that I look for the Keystone. The Keystone is an asterism within the constellation Hercules. Look at the header picture, the “almost” square in the centre of Hercules is the asterism.
Last night (30. April – 01 May) I went out just before midnight, letting my eyes become accustomed to the dark. I had binoculars and Stellarium in night mode (showing red).
I know where the best guide star for Hercules is, Vega in Lyra (I learned that last week, waiting for the meteor shower). I used it to find Hercules. The moonlight was so bright that it was difficult to see the stars, so I ended up using binoculars to focus in.
I’m fairly confident that I found the Keystone, but could only confidently see three of the four stars that made it up. I understand that the fourth star is the least bright, and it could definitely have been overshadowed by the light of the moon.
I think it is fair to say that the hour I spent looking for and at the keystone asterism was well worth it, and I will definitely have another go when the moon is absent.
Bills Posts 