On Sat, Jan 18, 2014 at 10:09 PM, David J Taylor < david-tay...@blueyonder.co.uk> wrote:
> I am looking for a physical clock (not software) that will indicate local > solar time. IOW when the sun is at its highest point, the clock would > reliably read 12:00 throughout the year. > > Is there a commercial product or kit available for this? > For a mechanical clock, probably not. The problem is demonstrated by what I suggested that you do with a stick and pebbles. By marking the position of the sun to locate the point where the sun is highest in the sky you identify local solar noon. By marking the position of the sundial's shadow at a fixed time every day relative to GMT you will find that, over the course of a year, your shadow will inscribe an analemma, whose lateral displacement represents the correction factor between sidereal (GMT) noon and local solar noon. This is all caused by the tilt of the rotational axis of the earth which causes the poles to be displaced either advanced or retarded relative to the centroid at the equinoxes. (Equinoxae?) So your mechanical clock would need to speed up and slow down in a smooth fashion twice over the course of a year. Pretty hard to do with a mechanical clock. Definitely a job for a uP. BUT a really cool thing would be to interface a camera to find the point in time where YOUR local noon actually occurs and corrects the clock. Automatic meridian circle anyone? -- Brian Lloyd, WB6RQN/J79BPL 706 Flightline Drive Spring Branch, TX 78070 br...@lloyd.com +1.916.877.5067 _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.