## Analemma – Activity #1

So – here is the drawing I made from the dimensions of my apparatus, and the distances to both the equinoxes and the solstices.  The side marked “Gnomon” is the measurement from the ground to the height of the stick (gnomon).

I then measured the distance from the gnomon to the dots corresponding to the equinoxes and the solstices.

The drawing I used was full size. This drawing is just representative of my drawing. It’s not the actual drawing. It’s important for you to make the drawing full size in order to measure the angles for activity 1.

You will also need a protractor

For the first part of the activity – “measure the tilt of the earth’s axis using only your analemma and apparatus measurements.”

Take your protractor and measure angle a, then angle b. Then subtract b from a. This will be approximately 23 degrees which is the tilt of the earth’s axis.

Next – using your protractor measure the angle marked ‘latitude’. This is – you guessed it – your latitude!

Yea! One down  – three to go! Up next – Activity #2: with reference only to your analemma and measured dimensions of your observing apparatus, calculate the Sun’s path in the sky and produce a sketch or plot to depict that path.

Hmmmm – getting tougher!!

Amy

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

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