Arthur Carlson <[EMAIL PROTECTED]> writes: > [EMAIL PROTECTED] (John Carmichael) writes: > > > Let's say ... > > ... Will this technique produce the same shape hour lines at any > > time of the year? > > Yes. The hour lines will always have the same shape. This is even > true if the gnomon is not aligned with the axis of the Earth, as long > as it is straight.
Some other respondents have touched upon the question of the orientation of the gnomon. I stand by my answer to the question as stated: John's technique will "produce the same shape hour lines at any time of the year", for any straight gnomon. If you want to label these lines for clock time, the labels will have to change during the year. Or you can put labels on them that are valid for some day of the year and read corrections to these labels from a table. The advantage of a polar gnomon is that these corrections are just a function of the day of the year (the familiar Equation of Time). With, say, a vertical gnomon, the correction will depend both on the day of the year and also the time of day. (Obviously, I've been thinking too much about my Dali dial. I better go cool off my brain.) Art
