STEP 1 · SET OBSERVING LOCATION
Your location tells us what is above the horizon and when. Choose a place before calculating the sky.
Location is used for sky calculations. Your profile stays in this browser; no account is required. City search and weather requests go directly to Open-Meteo. Normal links do not share your saved location. Observing guide
Castor AB
Double star · Gem
Set observing location to calculate altitude, timing and practical visibility. This guide describes the object in general.
A tight, bright white pair — both components are similar in colour and brightness, so the pleasure here is purely in resolving two suns where the naked eye sees one.