At the solstices, the derivative of the declination goes through just about to zero, just like a sine wave.
-John ============== > It might be useful to determine the rate of the sun's movement at > the ends of the analemma. > > There is a passage grave north of Dublin, Ireland, that has a long > passage from a shadow box above the entrance to a spiral carving on > the rear wall. Light shines on the carving at the winter solstice. > > The waiting list to see this event fills up with New Agers about a > year before the event. I asked our guide if that wasn't very hard > on people who could only see the event on one day if that day was > cloudy. "Oh, no," she said. "The event happens for 3-4 days on > either side of the solstice." > > Of course, a passage grave is not the same as a shadow cast by a > fine wire on a microscope. It might take a few years to locate it > properly. > > Are there any timenuts that want to be buried in a passage grave? > > Bill Hawkins > > > -----Original Message----- > From: Chris Albertson > Sent: Monday, January 23, 2012 8:40 PM > > On Mon, Jan 23, 2012 at 6:07 PM, J. Forster <j...@quikus.com> wrote: >>> I think you'd want a slit, not a pin hole. The pin hole would be >>> better but it would only work one day a year. >> >> Actually two days per year, unless it was adjusted for the summer or >> winter solstice, then it'd be one. > > I still think it is "one". because there are not an integer number of > days per year so you don't get and exact repeat in 6 months. Maybe a > pin hole would only work once ever? I don't know. To "work" the > pinhole has to exactly line up with the detector at the exact same > time of day. > > But I'm not liking slits either because I can't see how to adjust them > to exact vertical. > > I'm back to the first thing I thought of, a wire with a large weight. > Then you measure the light curve as shadow of the wire sweeps over > the detector. > > > > _______________________________________________ > 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. > > _______________________________________________ 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.