Astrini is a mini-educational software designed to assist teaching of basic notions in astronomy by explaining the reason behind:

• seasons
• phases of the Moon and Earth
• eclipses of Moon and Earth

It is designed to be used in a short self-contained educational module. It may be used by the pupil on her or his own, but we recommend it for an use under the teacher’s guidance.

The key idea of Astrini is manipulation. Astronomy software (e.g. Stellarium) allows you to change your position in space and time, or to visualize stars below the horizon, but does not in general allow you to change any facts – it works like a virtual observatory.

Astrini, on the other hand, lets you modify some facts of in the model: the tilt of the Earth’s axis, and the tilt of the orbit of the Moon.

Astrini is thus not a virtual observatory. It turns Sun, Earth and Moon into toys one can play with. Why?

The actual parameters of the Sun-Earth-Moon system are a bit too complicated for one’s first steps in astronomy. By understanding how a simplified model works, one can create a confidence zone for understanding more complex facts. Access to these more complex facts will be triggered by the key question, why don’t things happen as in the model?

• Why don’t we have one eclipse per month?
• Why are day and night almost always of different length?
• etc…

We hope you will enjoy Astrini.