To anyone who might know:
Living in Tucson, Arizona, which has more minutes of sunshine
annually than any other spot in America, I became an amateur diallist a
few years ago. I
thought I'd put a question to you for your expert consideration.
For some time I've wanted to build a horizontal dial which reads
clock time directly. Normally, people who do this simply use equatorial
dials, as this is a simple process to merely adjust them to clock time.
Here is my theory: Could you look at it and tell me what you
think? What if (after properly calculating hour lines, and designing the
gnomon properly for your lattude) that you could mount the gnomon so
that it is properly oriented to the north but NOT ACTUALLY touching the
dial plate. That is to say, it sits a tiny fraction of an inch above the
dial
plate, anchored to an external point that lies to the north of the
gnomon. They could be for example, connected by a dowel rod. Now,
getting back to the dial plate itself. What if, at the junction of the
noon line and six-o-clock lines, we make a small hole...and then drive a
tiny rod into that hole so that the dial plate pivots around that point
on a base to which is attached? The point itself however, remains in the
same position relative to the gnomon. Could we not simply orient the
dial plate so that it reads clock time, knowing that it would have to be
adjusted every few days to account for the changing equation of time?
I've tested this theory by attaching a piece of thread connected to
a needle, driven the needle into the center of the noon/six-o-clock line
juncture so that the thread is flush with it, and then oriented the
thread to the north at the proper elevation to match Tucson's 32 degree,
15 minute latitude. I'm using a paper dial template which pivots easily.
After adjusting the template to read mean time, I stick thumbtacks into
it to keep in in position to avoid the effects of wind. Although it
seems to be working like a charm, I thought I'd ask around, hopefully
encountering someone with the astronomical background to positively
confirm what seems intuitively to me to work fine. I'd appreciate your
consideration of this, as I've never heard of this method being employed
on a horizontal dial. Thank you, and keep up the good work!
Tex Brashear
