✽ What is an Analemma?

If you chose a fixed location and a fixed time to point to the Sun each day, you would find that over the course of a year your finger would trace out a closed curve resembling a distorted figure eight. When carefully plotted, astronomers call this figure an analemma…

The analemma above plots the position of the sun at 12:00 noon at the Royal Observatory, Greenwich (latitude 51.4791° north, longitude 0°) during 2006. The horizontal axis is the azimuth angle in degrees (180° is facing south). The vertical axis is the altitude in degrees above the horizon. The first day of each month is shown in black, and the solstices and equinoxes are shown in green. (The analemma’s width is scaled to exaggerate the effect.)

Of course, the real thing always looks more impressive than a boring graph…

The roughly figure eight shape of an analemma is primarily a result of two factors: a) the tilt of the earth’s axis, and b) the slightly elliptical (rather than circular) shape of the earth’s orbit. The following animation explains the effect much more easily than my words could. In fact, if you ask me, it is a pedagogical work of art! Even so, you might have to study it for a while to understand what’s going on…

But the climax of this footnote is due to a guy named Robert Nufer. From his bedroom balcony in Therwil, Switzerland, he set up a fixed computer-controlled digital camera and photographed the Sun through a Mylar solar filter every 60 seconds between July 2013 and June 2014! This resulted in around 180,000 images, which he organized into a series of analemmas, separated by 60 second intervals. The resulting video is simply spectacular…

BTW, I started that video at the juicy part for you, but there’s a lot of useful background information in the first part if you want to scroll it back and watch it from the beginning.

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