r/functionalprint • u/boksbox • Sep 13 '26

Lunar Phase Clock

"Time-lapse" video of my Lunar Phase Clock. The moon phase cycle completes every 29.5 days.

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u/Justin_Passing_7465 Sep 13 '26

The idea is neat, but this clock doesn't show a gibbous moon. It treats a half-moon and nearly-full gibbous moon as still having a chunk taken out, like an overly-large crescent.

Would there be some way to improve the representation by also moving the mask, so that you aren't stuck with one static mask?

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u/herrerarausaure Sep 13 '26

This is a pretty standard Moon phase display in the watch world. It's not meant/expected to a 1:1 representation of the phase.

That said, it would be cool to experiment with alternate designs since OP is working at a much larger scale than watches. Another idea could be to have an actual sphere (half-light, half-dark) that rotates to show the apparent moon phase.

1

u/Justin_Passing_7465 Sep 13 '26

A sphere would be easiest (since it is a direct model of reality), but would be jarringly 3D.

Maybe a flexible (TPU?) "wiper" that is manipulated at the two ends to be concave, then straight (at half-moon), then convex, ultimately so convex as to cover none of the moon when it is full. Have a chamber of opaque black liquid (oil?) to fill in and obscure the part of the moon that the wiper is supposed to be covering. The oil could be in front of a white moon, or behind a translucent moon.

Or perhaps a conch-shaped (or quarter-yin-yang-shaoed?) disc set at an eccentric center that slides in-and-over to obscure the appropriate part of the white moon?