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The Solar Analemma over Edmonton

What is the solar analemma?

If observed at the same time each day, in the course of a year, the Sun's position in the sky traces a figure-8 shaped curve called the "analemma". The analemma is produced by the combined effects of the Earth's tilted axis of rotation and its variation in speed along its elliptical orbit around the Sun. Over the year, the Earth's axial tilt shifts the Sun's position north/south and the Earth's elliptical orbit shifts it east/west. Solstices correspond to the top and bottom of the figure-8, indicating the northern and southernmost limits of the Sun in the sky. The cross-over point on the curve is around both April 12 and August 30 as the Sun's apparent position ascends and descends respectively. The analemma curve is also a graphical representation of the equation of time which describes the difference between sundial time (apparent solar time) and clock time (mean solar time).

The Project

It started as a project to capture the solar analemma on a single frame of film in one year. Difficulties turned it into a 4-year saga. Along the way, camera mounts moved, park benches were replaced, Kodak stopped making film, and Murphy showed up a few times. And for even more fun, I added a parallel digital analemma sequence to the project! The results are:

A film-based image. The traditional goal of getting all on a single frame of film. See it on my FLickr Page.

A digital image. The digital way of doing it results in a similar composite image. See it on my FLickr Page.

A timelapse movie showcasing the analemma and the changes of the four seasons in Edmonton. Watch this 2-minute video on YouTube, best view in HD with sound.

 

 

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