Greg takes a good look at the moon and makes an aspect of it physical. very cool!
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But unlike a true lunar phase, the occlusion disk mechanism simply nibbles away at the rotating moon's image - never spanning from pole to pole until the moon is fully covered. Never changing in curvature. Never a staight line at quarter-moon
Most lunar watches implement miniature versions of the tall clock "double bosom" occlusion mechanism. Sometimes, by expanding the gear train, they tick out a more accurate lunar cycle of 29.53059 days (slipping by a day once every century or so). Even so, these modern lunar watches remain infested with mice, nibbling away at the corner of a moon made from cheese:
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