Satellite Transit Finder

Calculate when a satellite crosses the face of a celestial body near your location. Uses SGP4 propagation and astronomical ephemerides to ray-cast shadow lines onto the Earth.

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Latitude Longitude Altitude (m)

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Satellite or NORAD in Celestial Body

Days Radius (km)

☀️ Photographing Solar Transits

Solar transits last under a second — the ISS crosses the Sun's disk in 0.3–0.8s at ~7 km/s. Use a proper solar filter (Baader film, Thousand Oaks glass) on the front of your lens. Shoot at 1/1000s or faster, burst mode or video at 4K 120fps. A 500mm+ focal length fills the frame with the solar disk. Manual focus to infinity, pre-framed on the Sun.

Guides

🌙 Photographing Lunar Transits

Lunar transits are trickier — the satellite is a dark silhouette against a much dimmer surface. No solar filter needed. Use 1/1000s–1/2000s, ISO 400–1600 depending on Moon phase. A waxing gibbous or full Moon gives the best contrast. The ISS appears as a sharp black dot against the bright limb. Video mode at high frame rate is more forgiving than single shots.

Guides

Tips

Timing is everything — the transit window is typically <1 second. Use an audio cue or GPS-synced clock.
Check TLE freshness — orbital elements drift. Re-calculate on the day of the transit for best accuracy.
Path width matters — the visibility strip can be as narrow as 2–5 km. GPS your exact observing position.
Practice framing — set up and focus well before the transit. The Sun/Moon won't move much in 30 minutes.

Satellite Transit Finder

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