‘Gordon's Sun Clock’ is essentially a single-hand watch with a dial that changes daily, based on the rhythms of nature and the stars. It shows the position of the sun and the starry sky. It is a new way of displaying time that is not artificial like our normal clocks (with railway time and daylight saving time), but moves in harmony with the seasons.

–– Your view:

In the middle of the screen, you will see a horizontal line. This is the horizon (the surface of the Earth). The pointed triangle in the middle is a spruce tree that you see from a distance (or a church). (You are not looking down on it from above, but standing in front of it.)

If you have not changed the settings (‘View direction: automatic’), you are looking south in the northern hemisphere (and north in the southern hemisphere). Objects on the left side of the screen are located in the east; objects on the right side of the screen are located in the west (reversed in the southern hemisphere). The cardinal directions are shown at the edge of the horizon.

The (light) grey strip below the horizon indicates the (civil) twilight phase. The large, dark grey area symbolises night (including nautical twilight). Objects located in this area are not visible.

On the right edge of the screen, you can see the local time (in digital form), the GPS position of the location as a numerical code (e.g. ‘cri-hs’, which is accurate to approx. 4 km) or a place name (if you have entered one), as well as the current altitude of the sun in degrees in the sky (e.g. 27.6°).

–– Sun:

The sun (at the end of the clock's single hand) moves from left to right (reversed in the southern hemisphere) throughout the day. The further to the left the sun is on the screen, the further east it is; the further to the right, the further west (reversed in the southern hemisphere). The higher the sun is on the screen, the higher it is in the sky.

The sun follows the circular path marked on the screen, which it travels along in the course of a day. The hours are indicated at the edge of the circular path (e.g. ‘12’ o'clock), so that the circular path also functions as a clock face.

On the clock face, for example, you can see how the numbers shift during the time change, but the circular path remains the same. Or: how the legal time in most places differs from the local time, as 12 o'clock is not exactly at the top of the clock face.

–– Moon:

The moon also has an orbit. It is drawn as a light grey circle (without a pointer). Since the moon takes more than 24 hours to complete one orbit, two additional hours (from the previous day) are added in extra light grey. If you ‘live with the clock’, you can clearly see how the moon periodically rises and falls over the course of weeks. You can also observe how it is opposite the sun in the circle position (far away) at full moon, but at the same circle position (close to the sun) at new moon. It is usually not exactly the same position because you are looking from the side (and not from above). The exact same position only occurs during a solar eclipse.

Full moon and new moon are indicated (by the shaded area). New moon is shown for 35 hours (because that is the time during which the moon cannot be seen at all). Full moon is shown for 24 hours.

–– Accuracy:

All calculations are performed for your local location and should match the positions in the astronomical almanac to within 0.0005 arc seconds (the moon is approx. 2000 arc seconds in size).

In the latest version, the Agnihotra times are calculated for your local location (also possible with GPS). There is also a countdown timer that counts down to the next event with second-by-second accuracy.

Gordon's Sun Clock is also called Astronomical Clock, Astronomy App, Horologium, Horologion, Orloj, Astrolabe, Astrolabe Clock, Star Clock, Sky Clock, Single-Hand Clock, Solar Clock, Sundial. It includes Skyfield and Agnihotra Timer.