Sunday, February 27, 2011

Celestial Geometry and Birdhouses

We've decided to encourage the tree swallows to settle in our valley again, this time in nest boxes high up on slippery poles. That should prevent the snakes from getting the young.

We also decided to increase the number of boxes in the hopes of increasing the number of cheer-bringing birds. 12 seems like a good number, and makes for an interesting construction challenge.

As long as we're making a new feature on the land, I'm taking it upon myself to practice celestial navigation and surveying geometry. I'm planning the 12 new posts to lie evenly on a circle that's oriented to true North. We're doing the orientation and construction using only two pieces of string and our eyes.

We had chosen our center location and a radius that would have the nests far enough away from each other and the places where people travel. Then, we were just waiting for a clear night to find North.

Last night, I woke up at 4:00 AM to find the sky crystal clear. It was a perfect time to go out and sight the center line. I drove a stake lined up with the center stake and Polaris to capture the North line.

This morning, Wispr and I went out with some wool yarn to place the rest of the stakes. The first thing that we noticed was that the radius stake, which we had placed "roughly" in the north, was absolutely dead on. I guess we have a better understanding of North than we had thought.

With the 12:00 stake placed, we used line-of-sight and one of the radius strings to place the 6:00 stake.

With the center, 12:00, and 6:00 stakes in place, we can use two copies of our radius string to place the rest of the even-numbered stakes. We now have a hexagon oriented to North.

The next step is a specific to the medium - fold one of the radius strings in half and tie a knot. Now, when that string is stretched between any pair of even-numbered stakes, a radius from the center that passes over that knot will give us the location of the odd-numbered stake between them.

And, that's it! Now we can dig the post holes and sink our poles to create a near-perfect 12-pointed circle aligned to North.

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