Before the days of GPS mariners, airmen, explorers and surveyors found their position by the sun, moon, planets and stars. Join blue water cruiser Frank Petrie to learn the basics of navigating with a sextant, and why it’s harder than Hollywood would have you believe, at the planetarium show “Navigating by the Stars – Celestial Navigation Isn’t Like What You See in the Movies.”

The show is 7:30 p.m. Saturday, Dec. 10 at the Edwin E. Ritchie Observatory in Battle Point Park.

There will also be a Stellar DNA Kids Shows at 5 and 6 p.m. with Dr. Erica.

If the sky is clear, astronomers will be on hand with telescopes for public star or sun gazing afterward.

Admission is free to members of the Battle Point Astronomical Association; $2 donation suggested for nonmembers, $5 for families.

The BPAA is a nonprofit amateur astronomy organization that operates the Ritchie Observatory and John H. Rudolph Planetarium in the Helix House at Battle Point Park.

For more information, call 206-842-9152 or visit www.bpastro.org.