How to Read the Astronomical Clock
A guide to understanding the astronomical clock displays
●Quick Start (60 seconds)
This clock shows you something most modern clocks hide: your relationship to the cosmos.
- ☀️golden Sun hand shows where the Sun is in the zodiac right now—and your local solar time.
- 🌙Moon indicator shows the current lunar phase and zodiac position.
- ♈outer zodiac ring shows the ecliptic—the Sun's path through the sky over the year.
- 🌍Earth map shows day and night across the planet right now.
☀️The Sun Indicator
The golden hand with the Sun symbol points to the current zodiac sign the Sun occupies. This changes roughly once a month as Earth orbits the Sun.
The Sun's position also indicates local solar time—the time based on the Sun's actual position in your sky. When the Sun is at its highest point (solar noon), that's 12:00 solar time, regardless of what your clock says.
Why does solar time differ from clock time? Time zones are artificial conveniences. Solar time varies continuously with longitude—your solar noon might be 12:15pm or 11:45am by clock time, depending on where you are within your time zone.
🌙The Moon Indicator
The Moon indicator shows two things: the current lunar phase and the Moon's zodiac position.
The Moon completes a full cycle of phases in about 29.5 days (a synodic month). As it orbits Earth, we see different amounts of its sunlit side:
The Moon also moves through the zodiac, but much faster than the Sun—it completes a full circuit in about 27.3 days (a sidereal month).
♈The Zodiac Ring
The outer ring displays the 12 zodiac signs, each spanning 30° of the 360° circle. This represents the ecliptic—the apparent path the Sun traces across the sky over a year.
As Earth orbits the Sun, we see the Sun against different background constellations. The zodiac signs are these constellations, named thousands of years ago by Babylonian astronomers.
Astronomical vs. Astrological zodiac The zodiac shown here is the tropical zodiac used in Western astrology, which is fixed to the seasons. The sidereal zodiac (used in Vedic astrology) accounts for precession and differs by about 24°. Astronomically, the Sun also passes through Ophiuchus, a 13th constellation not in the traditional zodiac.
⏳Unequal Hours
Before mechanical clocks, people used unequal hours (also called "temporal hours" or "planetary hours"). The day was divided into 12 hours of daylight and 12 hours of night—regardless of how long daylight actually lasted.
This means in summer, when days are long, each daylight "hour" might be 70-80 modern minutes. In winter, daylight hours might only be 40-50 minutes. Night hours would be the opposite.
Why did people use unequal hours? Without artificial lighting, life was structured around sunrise and sunset. Dividing daylight into equal parts made practical sense for scheduling work, prayers, and meals—even if those parts varied with the seasons.
🌍The Earth Map
The Earth map uses a polar azimuthal projection—imagine looking down at Earth from above the North Pole. This view clearly shows the day/night boundary (the terminator) as a circle.
Two special points are marked:
- Subsolar point (☀️): Where the Sun is directly overhead. This point traces a path between the Tropics of Cancer and Capricorn throughout the year.
- Sublunar point (🌙): Where the Moon is directly overhead. Because the Moon orbits faster and at a different angle, this point moves more dramatically.
Your location is also marked. The terminator line separates where it's currently day from where it's night.
📖Glossary
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