spacetime.watch• Apr 22, 2026• 1 min read
Show HN: Spacetime Watch – an astrolabe-inspired astronomical Wear OS watch faceThis is an unconventional clock concept, with a North Pole-centered azimuthal world map that rotates counterclockwise once per day, just like the Earth does around its axis when viewed from the north. This makes it possible to see roughly what time it is everywhere on Earth at once. The clock hand is the central longitude of your time zone.The star map is also shown, in the same projection, as an overlay. The Sun, Moon and planets are also shown, with accurate ecliptic longitudes to within 1 degree max error, but with their ecliptic latitudes ignored – that is, they are snapped to the ecliptic circle for a cleaner look. The star map makes one clockwise rotation once every year, so that the Sun stays roughly at the top of the watch face.Since the clock's direction is counterclockwise, the hour hand will point right in the morning, up at mid day, left in the evening, and down at night. This takes some getting used to, but in my opinion, this is the direction clocks ought to go, since it
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