The Astronomy Picture of the Day for 2014 March 20 is a solargraphic pinhole
analemma for Wrocław, Poland, as elegant an example as I've seen. I admire the
dedication of the photographers with this multiple exposure!
http://apod.nasa.gov/apod/ap140320.html
The noon analemma is near vertical since Wrocław is just 2 degrees from the CET
meridian. Those to the left and right are an hour and a half before and after
noon, meaning just a 15s daily clock error relative to mean solar time would
skew one figure 8 on top of its neighbor. While a fraction of a second secular
error per day would be enough to show a discontinuity on the calendar date that
the project began and ended since 1s/day is 6 minutes per year, a large
fraction of the width of Earth's equation of time.
Conversation starters:
• How would the picture differ if the pinhole shutter were timed by a
sundial?
• How if by sidereal clock?
Rob
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