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Miniature Inner Planet Orrery

An orrery is a mechanical illustration of the relative movements of planets in orbit around our Sun. This miniature inner planet orrery shows the planets Mercury, Venus, Earth, and Mars in orbit around the Sun, along with the Moon orbiting the Earth. Designed to fit in one hand, the orrery is 4 inches across and driven by a knob at the bottom of the mechanism.

Inner Planet Orrery Picture

As the Earth orbits the Sun, its Moon revolves about the Earth 12 times per year.

Inner Planet Orrery Ecliptic Plate

The ecliptic plate displays the month names, zodiac symbols, and zodiac constellations.

Orbital Periods

 Planet Orbits per
Earth Year
Actual Orrery
Mercury 4.150 4.125
Venus 1.625 1.625
Earth 1 1
Mars 0.532 0.537

Conversation Topics

Orreries as teaching devices facilitate many conversations about how our solar system works and movements of the planets. Two interesting topics that can be facilitated by this orrery are about Mars.

In ancient times there when the Earth was assumed to be the center of the Universe philosophers needed epicyclic components to explain why Mars sometimes appears to reverse direction in the sky. Using this orrery, the relative motions of Earth and Mars can easily demonstrated.

In current times there's more interest in the possible human exporation of Mars. Getting to Mars on the shortest possible path requires that a launch from Earth be timed to catch up with Mars later in its orbit. This transfer orbit can be illustrated with the orrery.

For Sale

Armstrong Metalcrafts has built a limited number of these for sale. The price is $495. To inquire about a purchase, please use our contact form or send an email to "sales" at

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