Being a practical guy, I needed a hands-on way to assist my explanations to others, never mind helping me to understand what I was explaining.

My first model was a simple one to demonstrate not only how the Southern Cross helps to find South, but also how it changes its orientation through the night and through the seasons.

The next model I built was to help explain retrograde movement of planets – that is, why they stop their usual movement among the stars going from west to east and for a short while move from east to west before resuming their usual direction.

When explaining the positions and movements of planets, it helps to be able to imagine yourself rising millions of kilometres towards the north or south celestial pole and looking down on the solar system. That ‘mind experiment’ helps make sense of a planet’s path across the sky – one can even imagine the planetary orbits being hoops straddling the night sky or, in the case of Venus and Mercury, slipping between Earth and the Sun.

Humans are Earth bound and ‘down’ is in the direction of the ground beneath our feet. It takes very difficult mental gymnastics for many, especially the beginner, to imagine the situation where they are standing 'sideways' on the 'side' of the Earth or 'upside-down' on the ‘underside’ of the Earth. This model helps to overcome this hurdle.

The closest I could get to this mind experiment was to build a model which shows how the planets move and where their orbits are relative to Earth’s orbit. This model easily explains why Venus is never seen overhead and why it alternates between being a morning star and at other times being an evening star?

The model has been in use for nearly ten years and helped me to clearly explain why the planets appear where they do in the night sky. Its exceptional usefulness demands that it be available to a wider audience, hence the creation of this booklet. The booklet provides detailed instructions on how to build and use the model.