Re: Azimuthal dial

[rw]

Wow, this is a very interesting type of sundial!   In a sort-of similar manner, would this also work:   Instead of a -line- for the gnomon, the reading is taken from a point along the line--perhaps a bead or thicker part of the gnomon, though probably more accurately, even the tip of the gnomon's shadow itself.   Then, for each hour the actual figure-8 of the analemma is put right onto the dial plate itself (warped, of course, to account for the type of dial plate).  Concentric circles could show exactly the path the bead's (or tip of gnomon's) shadow will follow.  So then, when the shadow is low on the dialplate, the reading comes from the bottom of the analemma, and progressively higher as the shadow migrates upwards through the year.  Of course, since there is nearly always TWO possible marks for each hour, either the two S-halfs of the figure 8 could be somehow marked as to the time of year, or else two BEADS could be used, and the two S-halves would be placed on separate dial plates--Thus for one half of the year, read from one bead and plate, and for the other half, read from the other.   I think it MIGHT work at low latitudes, also, if the bead was suspended above the dial plate.   I don't know all the sundialing terms or equations yet, but in my mind this works.  If it makes sense to anybody, am i on the right track?   Oh yes, one other thing--for a great math tutorial (aside from the one that is provided by one sundial website, somebody mentioned), from Algebra to Trigonometry and more, I have found www.gcse.com to be very good.  I've been re-learning forgotten math from their site recently.  The only problem with their site is that they use extensive _javascript_ing, so I don't suppose everyone would be able to visit.  I am not sure the top level of math taught there, though.   Have a great day! ryan weh ----- Original Message ----- From: fer j. de vries To: sundial Sent: Thursday, January 20, 2000 11:47 AM Subject: Azimuthal dial Hello Dave, Attached ia an example of such a dial. Spin means spider. The dial is for latitude 52 degrees north, longitude 5 degrees east, time meridian 15 degrees east ( our wintertime ) ( In summer we use 30 degrees east as time meridian ) You don't need a nodus, but just a vertical rod in the center. Read where the shadow of the rod intersects the circle of the proper date. At low latitude this type of dial isn't very useful. Best, Fer. Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat.  51:30 N      long.  5:30 E ----- Original Message ----- From: Dave Bell <[EMAIL PROTECTED]> To: fer j. de vries <[EMAIL PROTECTED]> Sent: Wednesday, January 19, 2000 9:46 PM Subject: Re: Dali dials > Hello, Fer! > > > In my programs suite zwvlak95 there is a program spin.exe to calculate such > > a dial for a horizontal plane with circular scales of date and a vertical > > style. > > You also may name this type of dial an azimuthal dial. > > Can you give me a mental (or real!) image of this dial? I had never tried > 'spin' before, and the result is, to say the least, interesting! Is this > basically a flat dial, with a vertical style and nodus? How would one > derive the height from the drawing? > > Thanks! > > Dave > > Fer J. de Vries [EMAIL PROTECTED] http://www.iae.nl/users/ferdv/ Eindhoven, Netherlands lat.  51:30 N      long.  5:30 E