At 55N, it apparently varies for a total of 90 degrees (centered on east), which is half the horizon from north to south! That's quite a bit of error if a lost camper is using the rising sun as east!
I think of the arc of the sun throughout the day as a hoola hoop that is surrounding a beach ball. On the equinoxes, the hoola hoop is split in half as seen from earth, and the opposite points are exactly at east and west. At the solstices, the hoola hoop has slid to the north and so more of the hoola hoop can be seen. That's my high tech explanation!
On my little Sundial Page is a link to "The Analemma for Latitudinally-Challenged People". It has clear explanations for this sort of thing.
Albert Franco
35N 95W
tony moss <[EMAIL PROTECTED]> wrote:
Noam Kaplan queried:
>
>2) Also, why does Waugh write that the sun will never shine on a vertical
>direct south dial before 6 AM or after 6 PM? If sunrise is at 5 AM
>wouldn't a shadow be cast on a vertical direct south dial?
>
What you need is a copy of Mike Shaw's 'Universal Dialist's Companion'. This simple device is settable for any latitude and solves all such mysteries in graphical terms that are easy to see and understand. My own copy is always to hand to get me out of conceptual knots.
Your puzzlement may arise from the mis-concept that the sun always rises due east when if fact during the summer it rises and sets well north of east/west. My UDC tells me that on midsummer day the sun rises at my latitude - 55 north - at just after 3.0am (GMT) and at a point on the horizon approx. 45 north of due east. Before/after 6.0 am/pm ! it is shining on the north face of an east/west wall.
You can contact Mike, with whom I have no business etc. association, for more info' perhaps at < [EMAIL PROTECTED] >
Tony Moss
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