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