Decorate biscuits with constellations
Plain round biscuits (Digestive or Rich Tea are good).
Icing Sugar (and food colouring if you like).
Water to mix with icing sugar.
Edible silver ball cake decorations.
Get the YP's to spread a teaspoonful of icing over the biscuit.
Using pictures of constellations as a guide, apply the edible balls to form constellations.
Try Orion, Cassiopeia & Ursa Major (The Plough).
Let the YP eat the biscuits only when a leader can identify the constellation!