Marine binoculars

10 May 2019

Apart from being a birdo and an astrophotographer, I’m also a scout leader. One of the things we teach scouts is navigation, and the other day I was planning an exercise.

It was pretty simple. The kids had to start at the kickoff spot on a footy oval, set the compass to a heading of 60°, and walk 100 steps in that direction. Then, they had to change direction, walking another 100 steps on heading of 300°. Finally they walk 100 steps due south. If they'd done it right, they should have found themselves back at the start.

Planning it, I was armed with a very old Silva compass, which was awesome in its day. However, it wasn’t playing the game any more. The alcohol had evaporated out of the central cell so the needle wobbled all over the place rather than staying consistently north.

I eventually got a reasonable result, but I couldn’t help wondering what would make the exercise better and more reliable.

The answer was to use a pair of marine binoculars.

The name “marine” is a bit much, really. Yes, they probably float, but they would have been just the ticket here as well. You see, the trick about walking in a certain direction is that you have to sight over the compass and choose something in the distance, like a tree or a post. My old compass was making this a real hassle.

Marine binoculars do this perfectly. You look through them, and turn on the spot while keeping an eye on the compass reading, which appears in one of the eyepieces. When this number is your required heading, what you need to walk towards is in the binocular view.

Don’t walk while looking through the binoculars – although I bet that some of the scouts would do just that!