Clocks Official Time

This clock shows the official time.’s official time is U.S. Eastern Time, or as it is more commonly known, The World’s Best Time Zone. It automatically updates for Daylight Saving Time. It was scripted and assembled in Flash, with vector and raster graphic elements created in Illustrator and 3D Studio Max. The code is original, but the movement of the hands is inspired by Microsoft’s Clock Sidebar Widget packaged with Windows Vista.


Latitude: 39.05
Longitude: -77.4833

This is v2.0 of the Astrolabe. v2.0 removes the hour, minute, and second hands which made the clock busier than it needs to be. v2.0 also redesigns the shape of the dragon hand, and corrects the shadow direction to match the rest of the site.

This clock is based on the ancient astronomical instrument of the same name. It functions similarly to the Pražský orloj in Prague, Czech Republic. It is an astronomical clock.

First, the image of the globe rotates so that observer’s longitude is pointing to 12 o’clock. There are two concentric circles centered over the pole. The smaller is the near tropic, and the larger is the equator. The far tropic lies at the edge of the image of the globe. The near tropic is Cancer in the Northern Hemisphere and Capricorn in the Southern.

Next, shaded areas over globe move to correctly indicate the horizon, based on observer’s latitude. The gold line between the unshaded globe and the light blue region is the horizon (0° elevation), and the gold line between the light blue and dark blue shaded regions indicates astronomical twilight (-18° elevation).

The large gold disc offset from center is a depiction of the ecliptic, projected onto a plane through the opposite pole. It bears the symbols of the zodiac.

The large yellow hand represents the sun. The position of the sun is indicated by the intersection of the outer edge of the ecliptic disc with the line running through the center of the long arm of the sun hand. The sun’s current position on the ecliptic (“sun sign”) is indicated by the zodiac symbols. The sun hand moves slowly counterclockwise (Northern Hemisphere) or clockwise (Southern Hemisphere) around the ecliptic. With respect to the ecliptic, the sun hand makes one revolution per year. The sun hand makes one revolution around the globe each day. When the sun hand and ecliptic indicate that the sun is in the dark blue region, it is night at the observer’s location. When the sun is indicated in the light blue region, it is astronomical twilight. When the sun is in the unshaded region, it is above the horizon. When the sun is indicated directly over the horizon, it is sunrise or sunset. Sunrise is to the left (right for Southern Hemisphere), and sunset to the right (left for Southern Hemisphere). The sun hand moves clockwise in the Northern Hemisphere and counterclockwise in the Southern.

The thin gold ring at the edge of the clock bears the names of the months. The position of the sun hand within the month indicates the current month and approximate date. The movement of the calendar ring approximately mirrors the movement of the ecliptic disc, but varies slightly with irregularities in the Gregorian calendar. The sun hand progresses slowly counterclockwise (Northern Hemisphere) or clockwise (Southern Hemisphere) through the calendar ring once per year.

The equinoxes and solstices are indicated when the sun hand intersects the outer edge of the ecliptic disc precisely above the equator (equinoxes) or one of the tropics (solstices). The solstice at the far tropic (outer edge of globe) will be the local winter solstice, and the solstice at the near tropic will be the local summer solstice.

The light gray hand indicates the position of the Moon in the same way as the sun. However, due to the ~5° inclination of the Moon’s orbit, the position of the moon only lies directly at the edge of the ecliptic twice per year (see discussion of dragon hand below). Therefore, there is a slight error in the Moon’s position that cannot easily be depicted with clock-like graphical elements. Moon’s position with respect to the sun, however, is very accurate. Phase of the Moon is indicated by the crescent-shaped shaded region lying just outside the calendar ring.

The short, blue, pointy hand is the dragon hand. It indicates the ascending and descending nodes of the Moon. These are the points at which the orbit of the Moon crosses the ecliptic. The ascending node is the node where the Moon is crossing the ecliptic from celestial South to celestial North, and the descending node is the opposite. These are the points where eclipses may occur. Eclipses are indicated by the sun hand, Moon hand, and dragon hand working in conjunction. An eclipse will occur whenever the center lines of the sun and Moon hands coincide with one another while within the little windows of the dragon hand. A solar eclipse will occur (somewhere on Earth) when the sun and Moon are at the same node (long hands coincide), and a lunar eclipse will occur when the sun and Moon are at opposite nodes (long hands opposite one another).

All astronomical calculations are from Jean Meeus, Astronomical Algorithms (2d ed. 1998) (with corrections through 2005). Globe map, tropic lines, equator, horizon, and twilight lines all drawn with Generic Mapping Tools. Hands, calendar ring, and ecliptic disc were drawn initially in AutoCad and colored in Illustrator. Bezel and cover glass were created and rendered in 3D Studio Max. Elements were assembled in Illustrator and animated in Flash. The Roman font is Engravers MT, and the zodiac font is Arial Unicode MS. The look is inspired by Ulysse Nardin’s Astrolabium G. Galilei wristwatch. Astrolabe uses the IP lookup API and database to find location based on IP address. If your IP is not in the database, Astrolabe will prompt you to go to to add it.

Flash and Illustrator are registered trademarks of Adobe Systems, Inc.
3D Studio Max and AutoCad are registered trademarks of Autodesk, Inc.
Windows Vista is a registered trademark of Microsoft Corp.

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