John Carmichael wrote: > Hello all: > > If we use a lunar sundial to determine the length of a lunar day (27 earth > days), and we are already familiar with the terms full, half and quarter > moons, then it would be convenient if there were 100 tics in a lunar day. > > If 100 tics equal 27 earth days then 1 tic = .27days = 6.48 hours = 388.8 > minutes. > > On the moon, the sun moves across the 180 degrees of sky in half a lunar > day: 27/2 = 13.5 earth days (50 tics). So, 50 tics = 180 degrees or 1 tic = > 50/180 = .28 degrees. > > If a good Tony Moss sundial has 1 minute accuracy on the earth, this means > it is accurate to 15deg./60 min. = .25 deg./minute. > > By coincidence, a high quality lunar sundial will be accurate down to the > nearest tic! (6.48 earth hours). >
I think John has made an error. If 50 tics = 180 degrees, then 1 tic = 180/50 =3.6 degrees. So a good Tony Moss sundial would be accurate to .28/3.6 or about 0.08 tics, which is half an earth hour. Chris Lusby Taylor Newbury, England 51.4N, 1.3W
