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What is an Analemma?

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  • Written By: Felicia Dye
  • Edited By: Heather Bailey
  • Last Modified Date: 08 November 2016
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Analemma is an astrological term. It refers to the path that a celestial body appears to move along when viewed from a set point. If, for example, a person charted or photographed the sun every day, at the same time, he would find that the sun’s position resulted in a recognizable path, also known as its analemma.

The analemma of the sun is often said to resemble the figure eight. It is important to understand that the appearance of the analemma varies depending on where you are. The path does not actually change. However, it will not appear to be the same from every place on Earth or from other places in the universe. There are several factors responsible for the difference.

The Earth tilts and rotates around the sun. The tilt of Earth is one of the factors that can cause the sun’s path to appear different than it seems from another planet. The path shown by an analemma makes it appear that the sun has moved, but this is not what happens. The sun does not move around the Earth. It only appears that way because of Earth’s movement.

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Describing the sun’s analemma from Earth as a figure eight does not mean it is a perfectly standing figure. The appearance of the path on Earth depends upon the observer’s longitudal position. The proportions of the northern and southern parts of the figure are affected by whether a person is in the northern hemisphere or southern hemisphere. For those at the equator, the sun should appear to travel along a horizontal path.

The observation of the sun’s analemma generally also considers the latitude of the sun. This is a measurement of how far north or south it seems. Charting the sun’s analemma with this piece of information can help a person determine the Equation of Time. This tells the difference between a clock’s time and the sun’s time. Every day does not actually span exactly 24 hours.

Most days are either longer or shorter than the 24 hours humans live by. There are only four days per year when the sun’s time matches clocks’ times. Those days are April 14th, June 20th, August 30th, and December 20.

There are several ways a person can track the sun’s path. He can use photographic images or make a graphical chart. It is also possible to make a physical model by using markers to record where the sun hits the ground.

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serenesurface
Post 3

@simrin-- Yea, I've seen the film and I do remember that scene!

I think you can draw an analemma that way. I don't think the hole needs to be big. The most important thing is to look out for the sun at exactly the same time. And you don't have to do it everyday, probably once a week would be fine.

You would need to look through the hole until you can see the sun and then directly mark that, down on the ground or something. Every time, it will be at a slightly different spot and eventually you'll get the figure eight!

SteamLouis
Post 2

Has anyone seen the film Castaway? In that film, Tom Hanks drew an analemma as he was marking where the sun shone through on the cave wall. I've seen that film several times but I had no idea that what he did had a place in astrology. That's pretty cool.

I wonder if it would be possible to do that at home? We actually have a hole in the roof of our garage. Could I possibly do what Tom Hanks did in the movie and draw an analema myself?

I guess the hole would have to be pretty big right? Otherwise, wouldn't I end up getting a straight line since I'm waiting for the sun to shine through the same place?

turquoise
Post 1

My photographer friend actually did this. He took a picture of the sun at the same time from the same place in his yard for an entire year. He then digitally put all of the pictures together to see the analemma graph.

I've seen the picture and it really does look like the figure eight but the circle parts are not equal. It's more like a really narrow number eight standing slightly side-ways with the top part of the eight much smaller than the bottom part. But I guess it wouldn't look exactly the same if it had been taken at another geographic location as the article mentioned.

The hardest part of this project has to be the patience and resilience it takes to carry on with it for an entire year without fail. This amazed me as much as the image of the analemma did.

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