Learn how Astronotify models celestial transits, computes orbital mechanics, evaluates meteorological conditions, and notifies you when observing conditions are optimal.
NEVER look directly at the Sun or observe a solar transit with binoculars, cameras, or telescopes without a certified, securely mounted solar filter (such as Baader AstroSolar Safety Film or a dedicated Hydrogen-Alpha/white-light solar telescope). Focusing unfiltered solar rays onto your retina causes instant, irreversible blindness and can permanently damage camera sensors.
The International Space Station (ISS) orbits Earth approximately every 93 minutes at an altitude of ~400 km and a speed of ~27,600 km/h (7.66 km/s).
The space station passes physically between your location and the surface of the Sun or Moon. The silhouette crosses the face in 0.5 to 1.5 seconds. High shutter speed photography (≥ 1/2000s) or video is recommended.
The ISS does not cross the disc itself, but passes close to the limb or through the solar corona. Excellent for viewing the flyby alongside a crescent moon or wide-field astrophotography.
As viewed from the surface of Earth, both the Sun and the Moon subtend an apparent angular diameter of approximately 0.53° (approx. half a degree) in the sky.
Because the angular radius from the center to the edge (limb) is ~0.26°, the separation distance reported on your dashboard is the angular distance between the exact center of the Sun or Moon and the closest point of the ISS trajectory:
Because the ISS is only 400 km away while the Sun is 150 million km away and the Moon is 384,400 km away, parallax is extreme. The ground corridor where an exact transit is visible is typically only 1 to 3 kilometers wide.
Moving just 500 meters or 1 kilometer north or south of the centerline can transform an exact transit into a grazing conjunction or complete miss. Always ensure your location's GPS coordinates are exact.
Astronotify integrates directly with the Open-Meteo meteorological API, pulling high-resolution numerical weather prediction models (including ECMWF, GFS, and DWD ICON) aggregated every day at midnight for your exact coordinates.
The Bortle scale measures the night sky's brightness and light pollution on a scale of 1 to 9:
Rural and pristine dark sky reserves. Milky Way casts diffuse shadows on the ground; zodiacal light and faint deep-sky targets easily visible.
Suburban transition skies. Milky Way visible overhead in summer, light domes present on horizons. Good for planetary, lunar, and bright nebulae.
City centers and inner suburbs. Sky glows orange or greyish white. Limited to the Moon, major planets, and bright double stars.
Tip: You can look up your location's exact Bortle rating using the interactive light pollution map linked directly from your location cards.
Astronotify automatically calculates the lunar phase and illumination fraction for each forecast date:
Nobody likes inbox clutter. Astronotify uses intelligent state tracking so you are only notified when real, actionable observing opportunities arise:
Each calendar night is timestamped upon notification. If a forecast's cloud cover fluctuates back and forth over several days, you will not receive repeat notifications for that same night.
If a transit is predicted during 100% overcast skies or heavy clouds (≥ 90%), transit alert emails are suppressed. The pass still appears on your dashboard marked with a “∼ Cloudy” warning. If the weather forecast clears prior to the event, the notification will fire.
Each location has independent toggles for Stargazing Alerts, Solar Transits, and Lunar Transits. Every alert email also contains a secure, one-click link in the footer to manage your preferences or unsubscribe without needing to log in.
Astronotify is committed to absolute data transparency and user sovereignty. Here is how your information is handled:
We do not track your activity across websites, utilize advertising networks, or install behavioral analytics pixels. We never harvest or compile telemetry on user habits.
Your account information and location coordinates are used solely to query meteorological weather forecasts and evaluate orbital geometry for the ISS passing across the Sun or Moon. Coordinates are sent securely in server-to-server weather queries without personal identifiers. We do not track your device GPS in the background.
Your data is never sold, leased, or shared with third parties or data brokers. We do not send marketing promotions, sponsored newsletters, or partner pitches. The only emails you ever receive are your chosen stargazing alerts, account security links (like password resets), and rare critical app announcements.
You can delete your account at any time from your Profile settings. When deleted, your account credentials, all saved observing locations, coordinate thresholds, and cached predictions are erased immediately from our databases. Only anonymous, non-personal aggregate counters remain so the platform's background processing stays stable.
Connect with fellow astronomy enthusiasts, request new stargazing spots, submit bug reports, or talk with the creators.
Real-time chats, astrophotography showcase, and feature voting.
Voluntary contributions directly offset server hosting, weather feeds, and satellite tracking compute.
Yes, Astronotify is 100% free to use for amateur astronomers and stargazers worldwide. We will never sell your data or clutter your observing forecast with ads. If Astronotify has helped you plan an astronomy night or photograph an ISS transit, small donations via PayPal help offset ongoing cloud server and domain renewal expenses.
Suggest Dark Sky Parks, nature reserves, or observatory viewpoints to add to our global curated directory.
Astronotify is an independent passion project run without advertisements. If you enjoy the tool, consider supporting server expenses.