Analemma from Albusciago, Italy

February 29, 2020

Analemma2016 (1)

Photographers: Paolo Bardelli; Luca Carlana
Summary Authors: Paolo Bardelli; Luca Carlana

February 2020 Viewer's ChoiceOur Planet makes a complete turn around the Sun in 365.2422 days. On average, one day (29 February) is added to the calendar every 4-years to catch up with this small delay. Like 2016, 2020 is a leap year.

Four years ago, Luca and I decided to photograph the Sun every day at noon (local time), from Albusciago, Italy. We were able to get 245 out of 366 useful shots (67 percent). The sum of these images produces the figure 8 form called an analemma. This is because the Earth's orbit is elliptical and not circular, the speed is not uniform (Kepler's laws) and the rotation axis is inclined by 23 degrees.

To photograph this analemma, we used a digital camera in an automated fixed location with a programmable electronic board. From a fairly complete analemma one can derive a considerable amount of information (for example, the positions of equinoxes and solstices, the symmetry of the seasons, etc.). The apparent motion of the Sun is faster towards the Northern Hemisphere’s spring and autumn but is almost zero in June.

Note that the path (apparent path) of our home star is in front of the constellations of the Zodiac. By the way, there are 13 constellations of the Zodiac, not 12. The thirteenth constellation is Ophiuchus, nestled between Scorpio and Sagittarius.

Photo Details: Canon 350d camera, zoom lens18/55 mm; 18 mm; with Astrosolar filter. Sum of 245 images - 1/250 second exposure; f/5,6, 400 ISO; Photoshop CC (Windows). Hardware and processing: Paolo Bardelli; Software: Luca Carlana.