

Parsec
A parsec is equal to 206265 astronomical units, that is to say, 3.26 light years. The scheme explains the calcul of a parsec : the semiangle obtained aiming at a star during a period equal to six months gives the distance calculated in parsec, knowing that this distance is equal to 1 parsec if the semiangle so obtained is equal to 1 second of arc.
 
