I'd just like to say a few more things about the portable folded-paper flat-dials. What interests me about them is that I like the Regiomontanus, as my favorite portable dial, and the most easily-built sundial of any category. But it's of interest how easily-built can be a portable-dial that doesn't lose accuracy near noon. ...because that could matter for modern urban applications, where public-transportation departures, appointments and events might be near noon. . I spoke of a 1-fold dial with a Horizontal-Dial on one surface and a vertical Polar-Dial on the other surface. I said that it wouldn't work in the manner that I'd described. I'd expected it to work with the top-edge of the vertical section as the gnomon, when use tipped-up as a Polar-Dial with both surfaces as polar-dial surfaces. . But it would work fine using a nodus at the middle of the connecting-thread (the thread that secures the right-angle fold). In that manner, it could work as a Horizontal-Dial and a vertical Polar-Dial, or, tipped-up, it could work as half of a Box Polar Dial. . A 2:1 paper rectangle is folded at the middle of its long-dimension, to make two mutually-perpendicular square surfaces. A thread connects the middle of their outer edges, and that thread has a nodus at its middle. . I call it the "corner-configuration" or "half-box configuration" . With one square horizontal, that square would have a Horizontal-Dial, and the other would have a vertical Polar-Dial. . Or the dial could be tipped up to make both surfaces polar-dials. . ------------------- . To summarize the 3 folded-paper dial-configurations that I've described: . These 3 configurations each forms half of a right-square-prism, cut in half by a plane through its axis (analogous to the half of a right-circular-cylinder comprising a Cylindrical-Eauatorial Dial. . With the 1-fold configurations, the user's thumb, resisted by the connecting-thread, can hold the 2 surfaces apart at a right-angle. ...which worked fine for all of my corrugated-cardboard Tablet-Dials. . Orientation about the vertical axis is by means of the declination-lines, labeled by declination or (preferably) by the approximate date for each 1/12 of the year's ecliptic-longitude variation. . 1. Corner-Configuration or Half-Box configuration: . As described immediately above. . With one plane horizontal, it mignt not be necessary to have a plumb-line for leveling. With both planes polar, a plumb-line could orient the dial about the NS & EW axes. . 2. Box-Configuration: . A 2:1 rectangle is perpendicularly folded-up a quarter of its length from each end. . A thread connects the middles of the top-edges of the up-folded ends. The nodus is at the middle of that thread. . Disadvantage: . The 3 folds complicate things for a folded-paper dial. ...in the matter of holding the up-folded ends perpendicular to the base. That adds a whole qualitatively different design problem to a folded-paper dial. . Advangage: . Potentially convenient use, by its resemblence to Cylindrical-Equatorial and especially to a Box-Polar (...which is what it is when tipped up as a Polar-Dial). . Orientation with respect to EW & NS axes is as for the corner-configuration. .
3. V Configuration: . A 2:1 or 1:1 paper square is folded at-middle into a right-angle V. ...hand-held, with the fold-crease in the plane of the meridian, with the two dial-planes tipped equally from the plane of the meridian. . As with the Corner-Configuration, the right-angle is held by a thread connecting the middles of the outer-edges of the two sections. The user's thumb holds the two planes apart, resisted by the connecting-thread. . ----------------------------- . Each of these 3 configurations can be used in either of 2 orientations: . Horizontal: . One plane, or at least some of the edges, is/are horizontal. . Polar: . All of the planes are polar, parallel to the Earth's axis. . ---------------------------- . Those combinations of configuration and orientation make 6 possible portable folded-paper flat-dials. . I'm not claiming that others aren't possible. . ---------------------------- . The 1-fold configurations would be much easier to build, given the problem of keeping the box-configuration's two up-folded ends perpendicular to the plane between them. . In the horizontal-orientation, the corner-configuration looks easier to use than the V-configuration, because the corner-configuration has a horizontal surface, giving it easier leveling even without a plumb-line. (My Tablet-Dials were all 5-minutes-accurate without a plumb-line or spirit-level.) . Especially for the polar-orientation, the V-configuration has appeal. ...though, even there, the corner-configuration might be easier to orient about the polar-axis, due to the ramp-like orientation of one of its planes. . --------------------------- . Of course, for the dials in polar-orientation the line-construction is much easier to explain. In fact, it practially doesn't need any explanation. . The horizontal-configuration of the V-configuration requires East-Reclining and West-Declining Dials for the two planes, making it the one needing the most explanation. . The corner-configuration and the box-configuration in the horizontal-orientation seem the easiest to use, because of the easy leveling of the horizontal surface. . ------------------------ . When I mentioned stationary dials, I didn't mention the Disk-Equatorial. I'm a bit prejudiced against it, because, for compelling reasons, the Disk-Equatorial is completely unsuitable for a window-sill dial. (...because of eye-injury-saftey considerations, and because of its lack of all-year readability on a window-sill). . But at an outdoor public place, it's readability from only one side could be called an advantage or an appeal, because it emphasizes solar-declination, when it's necessary to read it from the opposite side after an equinox. . Molded as a concrete block with a cylindrical hollow, the Cylindrical-Equatorial is much heavier than a Disk-Equatorial of the same dial-diameter. That's disadvantagous for transporting the dial, but is advantageous for discouraging theft of the dial. . It goes without saying that all the dials have their own different advantages and disadvantages. When a dial is proposed, the various dials' advantages and disadvantages should be told. ...and then it's up to the person or persons to whom the proposal is made. . 49 Tu November 26th 2353 UTC
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