Would it be possible to place 2 or 3 gnomons around the cylinder, whose shadows and timelines did not overlap (much), so that it would not be too confusing to tell which shadow and timeline to read during the different hours of the day?
Pete S. email: [EMAIL PROTECTED] home: http://netnow.micron.net/~petes ----- Original Message ----- From: fer j. de vries <[EMAIL PROTECTED]> To: Alain MORY <[EMAIL PROTECTED]>; Alexei Pace <[EMAIL PROTECTED]>; Roger Bailey <[EMAIL PROTECTED]> Cc: <sundial@rrz.uni-koeln.de> Sent: Sunday, March 05, 2000 2:45 AM Subject: Re: Cylindrical Dial > Hello Roger, > > You wrote : > > My suggestion to calculate the hour lines is to treat the cylinder like a > > polygon with a series of flat vertical faces. Calculate the lines for each > > face the usual way as a series of vertical declining dials. Lay out the > > design for each facet and draw a smooth curve through the mid points for > > each face to approximate the hour angles. > > Because a cylinder can be described mathematically it is rather easy to > calculate all the wanted points for a dial on the outside of a cylinder. > The cylinder also can be unfolded to a flat plane so a drawing can be made. > > It depends on the dimensions of the tower and the length of the gnomon what > the result will be. > > In the picture you see such a dial on a vertical cylinder with radius 250 > units with a perpendicular gnomon of 25 units, pointing south, for latitude > 45 degrees, reading local suntime. > The hourlines are curves, not straight. > > Best wishes, Fer. > > Fer J. de Vries > [EMAIL PROTECTED] > http://www.iae.nl/users/ferdv/ > Eindhoven, Netherlands > lat. 51:30 N long. 5:30 E
