The Battle Point Astronomical Association will present the planetarium show “Gaia and the Cosmic Ladder” at 7:30 p.m. Saturday, April 13 at the Edwin E. Ritchie Observatory at Battle Point Park.

The Gaia telescope has been measuring the distance to stars for six years. Astronomer Steve Ruhl will share details on the largest and most precise 3D space mapping project and the insight it provides for the size of the universe.

Admission is free to BPAA members; a $2 donation is suggested for nonmembers, $5 for families.

If the sky is clear, astronomers will be on hand with telescopes.

BPAstro Kids will join Dr. Erica Saint Clair for Slime Time from 4 to 6 pm.

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 go to www.bpastro.org.