Nilesh's Weblog

Analemma

What is an analemma? Well, if you photographed the sun once a week at the same time of day for an entire year, you would have a photo of the analemma, the sun's apparent path on the sky over the course of a year, which looks like a figure-eight.

The resulting photo is by your side. Ideally the shape of the figure should have been a slanted line across north-south directions. Then how does one explain this? There are two phenomena responsible for this `Analemma' - First As we all know, the earth is tilted at 23.5 degrees. This causes the seasons and the solstices (Uttarayana & Dakshinayana, as we call it). This causes the movement of the sun in the north-south direction. Second Earth's orbit is elliptical, not circular. Hence Earth's orbit speed is not constant. It varies periodically. This causes the additional east-west movement of the sun at the same time on different days and that we can observe. On some days of the year, at 12 noon, the sun is not exactly at the zenith, it is either ahead or behind schedule.

Isn't that interesting enough to take up as a photography project spanning one year? Yes, sure. But if you are still confused and need some animation/movies to get convinced, go to analemma.com.