wpo - a solar figure-of-eight analemma

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Letter to the Astronomy Now Editor ~1994

The photo [left-as published] shows my modest attempt to record the annual track of the sun across the sky by marking the shadow point cast from a corner of the porch roof at noon on clear days.   The sun-angle from London was too low from late September to early March and the markers fell on the distant shrubbery!   Small holes were drilled in the paving and pegs inserted for this picture.   The peg nearest the camera marks the start point on June 21st - the summer soltice - the track moving initially in a clock-wise direction to the left.  The Analemma demonstates that whilst the earth spins on axis with high precision, its orbital velocity along an elliptical path about the sun varies with the seasons so that the sun is not due south at each noon.

Maurice Gavin
Worcester Park Observatory - Surrey - UK.

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images & text copyright-Maurice Gavin-Mar 1994/2004