If a vertical dial is relocated and now faces a few degrees east or west of its designed declination, you might expect it to run a few minutes slow or fast. Has anyone ever tabulated the greatest error, and at what times and dates it occurs? And does it make sense to think about the average error? Clearly the errors depend on the latitude and the design declination, but for starters they could be tabulated just for a direct south dial at 52.5 degrees N, and for a location move of 1, 2 and 5 degrees either way. As the gnomon is no longer polar-pointing I imagine the maths is a bit hairy.
Best wishes, John Foad
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