12-18 years
Telescope in the pocket
困難: ★
Making your own sky disk
困難: ★
Form the armillary sphere to the astrolabe
困難: ★
The pyrenean shepherd’s dials
困難: ★
Building simple sundials
困難: ★
Latitude Gnomon and Guadrant for the Whole Year
困難: ★
Making helioscopes with four sticks
困難: ★