The moon will go dark on the evening of Jan. 20, and islanders are invited to join astronomer Steve Ruhl as he looks at the details of the dark moon and how to observe it.

Ruhl will lead the planetarium show “Dark Moon, Matter, & Energy” at 7:30 p.m. Saturday, Jan. 12 at the Edwin E. Ritchie Observatory at Battle Point Park.

Continuing with the theme, Ruhl will examine what we know about dark matter and energy, some of the darkest mysteries of the universe.

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

There will also be a special kids on “Musical Instruments” from 4 to 6 p.m. with Dr. Erica Saint Clair.

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

The Battle Point Astronomical Association 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.