On Sat, 5 Jan 2002, [iso-8859-1] Anselmo P?rez Serrada wrote: > Maybe some of you didn't notice that if you lean the mirror towards the > South so that it's slope equals half of your latitude then (a small > hand-made wedge would do the job quite well) you get a polar sundial > on the ceiling, with all its analemmas paralell to the meridian line...
I'm having a hard time visualizing this, this morning! I understand the mirror placement and tilt, but am not sure I see how this would yield a polar dial, with parallel analemmae. VERY nice idea, if it works, though! > By the way, I think the best method to draw the meridian line on the > ceiling of a room is the obvious one: consult in an almanac which is > the time for noon in this day for your place. Mark the bright dot on > the ceiling four hours later and four hours before that moment and > connect both dots: the mediatrix of this line approximates very well > the meridian line. > > Somebody's got a better idea? Sounds like an excellent suggestion. This would require a very accurately levelled mirror, though - perhaps John's mercury dish - or the effect of a tilted mirror would introduce a distortion, just as your first paragraph suggests... Dave 37.29N 121.97W
