Planetary moon
Also called: natural satellite, moon of a planet.
A natural satellite orbiting a planet — like Jupiter's Io or Saturn's Titan — seen as a star-like point next to it.
Jupiter's four big moons are visible in binoculars; Saturn's Titan in any telescope, and a few more of its moons with 6 inches or more. Mars's tiny Phobos and Deimos, Uranus's and Neptune's moons are hard tests that need big apertures and the planet's glare kept out of the field.
Moons change position from night to night — and around Jupiter from hour to hour — passing in front of the planet (transit), behind it (occultation) or into its shadow (eclipse).
In AstroPilot
AstroPilot shows where each moon is next to its planet tonight, with a slider through the night.