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A dial made by a clockmaker

Though this dial is not signed, it certainly came from the workshop of Philipp Matthaeus Hahn, of Ostmettingen, near Stuttgart. Hahn, who was a clockmaker, sold dials of this type for setting and checking his clocks.

There is a meridian ring, adjustable for latitude, and a rectangular brass frame rotating on a polar axis. Declination scales are engraved on plates at either end, together with the equation of time. One plate has two pin-holes and the rotating frame is geared to drive the hands of the watch-face. With the frame turned until the sun shining through the pin-holes throws spots of light on the correct points of the scale on the other rectangular plate, the time is indicated on the watch-face.

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