Astronomy Learning and Research / Beginning Astronomy / Observational Astronomy

The Analemma – Or, how I spent my summer vacation.

Analemma
Analemma

And my spring break, Christmas vacation, birthday and, well you get the idea.

So I spent the last year of my life running home at lunch, watching weather reports and planning when I could get the next dot on my analemma. So here’s the end result. Yes, that’s it.

I was thrilled to see the figure 8, however as you can see, I’m a little off center. It should be going straight up the center of the page. I’m a little off to the left. That means that I took my readings a tad early, a result of taking readings at noon by the clock. I should have used solar noon.

Solar noon is when the sun is at it’s highest in the sky. It actually happens at different times everyday, but you can calculate the ‘average’ time of solar noon. File that under ‘things to do differently next time’. HA – next time – I don’t think so!

Before I took it off the frame, I measured the distance from the tip of the gnomon to the dots marking the solstices and the equinoxes. I also had to measure the exact height of the gnomon.

These measurements are needed to complete the first activity, which is: with reference only to your analemma and measured dimensions of your observing apparatus, calculate (1) the tilt of the Earth’s axis relative to its orbital plane, and (2) your observing Latitude.

Easy right? Well as it turns out, not too bad! But you’ll have to stay tuned!

Amy

 

2 Comments

  1. Hello! I’m in the process of trying to figure out how to make my own analemma. I want it to be on the smaller side, which it looks like yours is. about how tall was your gnomon? Or do you know how to calculate how big the analemma would be, based on the length of the gnomon? Thanks for your time!

    1. Hi Ashleigh – The easiest thing to do is to go outside at noon. Bring the paper you want to use for your analemma and a pencil sized dowel. In fact, I may have used a pencil. The shortest day of the year is fast approaching, and is the perfect day to start your analemma! Go out a few days before, put the paper on the ground and stand the dowel up to create the shadow on the paper. Make sure the dowel is standing straight up and is on the edge of the paper, not too far away. I used a regular piece of standard sized paper, 8 1/2 by 11. My gnomon is about 4 3/4″ tall and is about 1/2″ away from the edge of the paper.
      I know there are some formulas out there, but I found my method worked quite well.
      Keep me posted on your progress, and if you have any other questions please let me know!

      Amy

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