25 June 1996
Hi there!
I'm a newcomer to sundials, so I would appreciate
your expertise. I'm trying to make a convenient, portable sundial
which does NOT require knowing the the direction of north. Using
the date, latitude and longitude are fine.
The two possibilities seemed to be either a shepherd's dial
or a analemmatic double dial. However, I've read some vague discussions
of ring dials which *seem* to suggest that they might serve as well.
I understand the ring dials which are just small armillary
spheres. I think I'm reading about a different kind, composed of
a *single* ring with a hole in the *rim*, and with *one* set of hour
lines on the inside of the ring. Like the shepherd's dial, I think
you align the ring with the sun; the light shines through the rim,
hitting an hour line on the far side. The seasons are corrected for
by moving the hole around the rim.
The only problem is that I compute that there is no possible
way to move the hole so that the sun falls on one set of hour lines for
all seasons.
Am I understanding these ring-dials correctly? I would appreciate
any suggestions people have.
Yours, Bill Wedemeyer
