Astronomical Sun Clock

A single-hand clock with a dial that changes every day – oriented to the Sun, Moon, planets and stars.

–– Why this clock?

My Sun Clock project has been evolving for more than 20 years. Behind it is an attempt to make time visible again as something local and seasonal, connected to the natural rhythms in which we already live.

The Sun does not change its clocks: I was bothered by the fact that at 12 o’clock it usually isn’t actually noon, by the clock changes, and by the fact that an ordinary clock tells you neither where the Sun is nor how the length of the day changes over the course of the year.

This led to an organic dial based on the actual path of the Sun at your location. The horizon runs through the centre of the clock, and the Sun’s path forms the dial. Sun, Moon, planets and bright stars share the same sky. In this way, the clock changes every day with the seasons. (Use the ↔ button to move time backwards and forwards; double tap to zoom.)

–– What can you see?

• Sunrise, sunset and twilight
• Day length and the Sun’s seasonal path
• Sun, Moon, planets and bright stars
• Local solar time and temporal hours
• Light-time seasonal calendar: eight phases of increasing and decreasing daylight throughout the year
• The major meteor showers
• Agnihotra times with countdown
• Time travel: move time directly backwards and forwards and watch the sky move with it – all the way to the night sky at your birth
• Optional weather overview
• Wall clock mode
• Works worldwide and offline
• Free, ad-free and privacy-friendly

–– A clock to live with

I have lived with this version of the clock since 2019. It has taught me to become more aware of natural rhythms: the angle of sunlight, the shortness of a winter day, the phases of the Moon and the starry sky. I feel connected to the bigger picture.

Astronomical knowledge was never the main purpose. The clock is intended to make visible again the rhythms to which we already belong. This clock is my gift to the world.

–– Two versions

Astronomical Clock is the lightweight web version of the Sun Clock: it runs on practically any device and lets you move through time directly and in real time. – For maximum precision, there is the more comprehensive “Gordon’s Sun Clock” using JPL ephemerides.

• Also known as: astronomical clock, horologium, orloj, astrolabe, star clock, celestial clock, solar clock, single-hand clock, temporal-hour clock