Dear Fred, How neat! I hope to hear more on this.
I've come up with a very simplified Equatorial Stab Dial that seems, so far, to overcome a number of the peculiarities of the dial as well as being very easy to fabricate. Very little sun here so far to test it. I'll send you more info when I've gathered more data on it's behaviour. Thanks! Edley Mcknight > One of the talks I will be doing at the next NASS conference will be on a > form of this dial that I developed in 1979 - and I've been toying with its > peculiarities ever since. > > Date and location of the next conference are not yet final - but we are > negotiating for an August date on the East Coast (of the U.S.) > > Fred Sawyer > > > > ----- Original Message ----- > From: "Edley McKnight" <[EMAIL PROTECTED]> > To: <sundial@rrz.uni-koeln.de> > Sent: Wednesday, November 26, 2003 3:30 AM > Subject: Stab Dial > > > > Dear Shadow Watchers, > > > > If anyone is interested in any "stab", "slit" or "groove" dials I'd enjoy > > communicating with them. > > > > Here is a short introduction to a couple of them. > > > > Stab Dials - One > > > > If one were to find, or place a round circular > > column so that it's length pointed toward the north or south > > celestial pole, one could create a sundial as follows: > > > > 1. Place a non-elastic cord around the column, marking where the > > ends crossed. > > 2. Divide the cord into twenty-four equal parts between the > > marks above. > > 3. At some exact hour of sunlight align a blade (of 47 degrees > > width and a half degree sharpness) for minimum shadow width with > > the blade width parallel to the axis of the column, blade > > centerline at right angles to the axis of the column, and sink it > > into the surface sufficient to hold it in place. > > 4. Place the cord around the column, aligning one mark with the > > blade and mark the 24 spots. > > 5. Re-sink the blade into the column at each mark corresponding > > to the hours of sunlight, keeping the blade width aligned up and > > down the column and the point directly toward the center of the > > column. Marking them to show the correct hours. > > > > When the blade is inserted into any of these stab marks it would > > indicate with a minimum shadow the correct hour of the day by > > local solar time, thus being a "shadow plane" dial. > > > > If the blade is lost, or off doing something else somewhere, the > > light reaching to the depth of the stab in the wood would > > indicate the same time. > > > > This is one kind of stab dial. > > > > If one makes the same stabs into other surfaces, maintaining the > > same alignment, it can be seen that they would work as well, even > > if the stabs were scattered about rather than in order. > > > > Since it is difficult to look fully into the stab marks, some > > people widen the marks into grooves roughly a quarter of an inch > > wide or so and find they work well also when fully lit. These > > seem to be commonly called "Groove dials" Others extend the > > blade tip just through a thick shell, putting a colored filter > > over the spot to indicate that certain time. > > > > I've come upon such insights from conversations and thought. If > > there is a body of written material on these dials or related > > ones, I would very much enjoy being informed of them! > > > > Edley McKnight > > > > 43.126N 123.358W > > > > > > > > > > - > > > > > - -
