Here is what I think: The can is laying on its side with its axis oriented north-south. A pinhole is made on the west side of the can (assuming this location is in the northern hemisphere, and that the zenith of the sun is toward the south), pointing upward at about 45 degrees. It captures the sun before it has reached solar noon, then tracks it all the way to sunset in the west. The tracks of the morning sun at the top of the picture appear to converge; this effect comes from that edge of the film being so close to can's the pin-hole, where all light rays converge at their origin. (The film is wrapped around the inside of the can)
-Bill On Mon, May 5, 2014 at 8:43 AM, John Foad <john.f...@keme.co.uk> wrote: > So . . . what is the explanation? From the angle of the tracks it looks > quite far north (or south). Can the curvature of the soup can do it? I > can't see how, whether it was vertical or horizontal. > > John > > -----Original Message----- From: Thibaud Taudin Chabot > Sent: Monday, May 05, 2014 10:11 AM > To: Sundial list > Subject: Re: Sun tracks > > > Do I see a retrograde? (Same azimut, different moments). Where is > this picture made? > Thibaud > > At 21:33 4-5-2014, Barry Wainwright wrote: > >> The BBC has a series of pictures taken by pinhole camera at >> http://www.bbc.co.uk/news/in-pictures-27221895 >> >> Image 7 is described thus: >> John Rigg: "This is a six-month exposure using a pinhole camera made from >> an empty soup tin and photographic paper, not film. The resulting image is >> then scanned and reversed. The trails mark the path of the sun across the >> sky as the seasons change. Days with broken cloud show as a dotted line." >> >> -- >> Barry >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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