Contrary to what I suggested yesterday, the adjustment of a sundial to give LTST at the standard-meridian doesn’t require solution of a system of equations. It’s a straightforward coordinate-transformation:
… Say the dial-plate is circular. For a sphere that circumscribes that dial-plate, the equatorial-coordinates on the sphere, of a point at the top of that sphere, are (Lat, 0). ... …where Lat is the latitude of the dial’s location, & 0 is defined as the longitude of the topmost meridian in the equatorial-system. … Now, say your location is 7 degrees east of your standard meridian. You want to change the equatorial-coordinates of that top-point to (Lat, 7). ... (…because let’s say that hour-angle (equatorial-longitude) is measured clockwise (westward) from the NS meridian, as it normally is.) … That’s the top-points coordinates in the equatorial system when the sphere has been rotated 7 degrees about its polar-axis, toward the standard-meridian. ... Now transform the top-point’s coordinates (Lat, 7) to the horizontal coordinate-system. … That gives you the azimuth & altitude of the top-point, as seen from the center of the sphere. … The dial-edge is a great circle on the sphere, all of which is 90 degrees away from the former top-point. … The place on the dial-plate that should be raised is the place 180 degrees from the top-point’s azimuth. … Raise that point by an angle equal to the complement of the altitude of the top-point On Sun, Mar 26, 2023 at 5:30 PM Steve Lelievre < steve.lelievre.can...@gmail.com> wrote: > Hi, > > Can anyone point me to an existing online calculator for making a wedge > to adjust a horizontal dial to a new latitude and longitude? > > I am not asking for an explanation of how to do the calculation; I just > want to be able to point people to a calculator that has already been > proved on the internet. It should use the original location (latitude > and longitude) and the new location to calculate the angle of slope of > the wedge and the required rotation from the meridian. > > Many thanks, > > Steve > > > --------------------------------------------------- > https://lists.uni-koeln.de/mailman/listinfo/sundial > >
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