Time at the Bodleian, Analemmas & Conjuctions

Lunch out in Oxford with Emma and Linda and then, while they travel to Bicester shopping village, I had some time at the Bodleian. A week or two ago I had emailed Richard Westman about an article from a book of his published in the mid-1970s. He didn't have a PDF file he could send me, but I was able to track down a copy of his book in the Radcliffe Science Library and could copy a couple of articles I wanted - Westman's Three Responses to the Copernican Theory: Johannes Praetorius, Tycho Brahe, and Michael Maestlin, together with Donahue's The Solid Spheres in Post-Copernican Natural Philosophy. I also worked through the first 12 volumes of the Journal for the History of Astronomy, preparing some entries for my working bibliography. All in all, a good afternoon's work

While travelling home on the bus from Oxford, I was reading an article in Astronomy Now about analemmas. These are multi-photo pictures, usually showing the view of the sun's position taken at the same time each day from a spot on the earth. The resulting picture shows a "figure of 8" curve. These curves have all sorts of interesting features. The narrower loop occurs during June each year (the peak of the curve being June 21st), while the wider loop cocurs in the Northern Hemisphere winter. That the two loops are not symmetrical is due to the earth's orbit around the sun not being circular but an ellipse. The earth's axial tilt results in the difference between the two extremes of the figure - the size of this difference being 46.5 degrees (which is 2 x the axial tilt).

It used to be the sign of an extraordinary camera operator is an analemma could be produced on one piece of film - indeed this was virtually impossible. Now, digital cameras and stacking software, make the task much easier. The internet has loads of really beautiful analemma pictures of course.

A rather nice variation, showing the sun's actual path on three days - it might be tempting to thick that the middle one is the equinox, but actually in occurs around early September and mid April. The equinoxes are half-way between the two extremes, and cross the bigger loop.

I always think to myself that I don't manage to take as many astronomical photos as I might like, but I was inspired by the above to process up the best pictures I took in early December of the Moon-Venus-Jupiter conjunction. Best two below.

The moon, Venus and Jupiter above the house - evening on December 1st

Not a very clear picture of the conjunction!