Know exactly when satellites pass above you.
AstroAlert is your personal sky-watch assistant. It tells you exactly which satellites, planets, comets, and deep-sky objects will pass right above your location in the next 24 hours — including spectacular zenith events above 70°. Powered by NASA/JPL data, it combines real-time calculations with educational content, a full astronomy glossary, and detailed object sheets. The sky above you, revealed with precision.
AstroAlert+ unlocks automatic alerts for remarkable sky events, notifying users at the perfect moment to observe. This eliminates the need to manually check the sky or research upcoming events.
AstroAlert automatically calculates which satellites, planets, and deep-sky objects are passing above the user's location using latitude, longitude, and timezone. It filters to show only objects rising above 70° altitude, ensuring only impressive sky events are highlighted. Users receive automatic alerts at the optimal viewing moment.
AstroAlert monitors 1,000+ satellites including Starlink constellations with fresh orbital data updated daily. Users receive notifications when these spacecraft pass overhead at optimal viewing angles, enabling naked-eye observation with context about each satellite's purpose.
AstroAlert+ provides over 1,000 celestial objects with full technical sheets, official NASA images, scientific data, historical context, and educational explanations. This transforms casual observation into learning opportunities about the universe.
AstroAlert combines real-time satellite tracking, planetary positions, deep-sky object catalogs, and automatic alerts in a single mobile app. Users gain a comprehensive view of their personal sky with scientific accuracy using official NASA ephemerides.