Predict when the Moon, planets, and asteroids pass in front of stars. For your exact location. Computed entirely on your device.
PhosphorOccult is a precision occultation prediction tool for amateur astronomers, IOTA observers, and serious stargazers. All calculations use established astronomical algorithms and a catalogue of nearly 9,000 stars from ESA Hipparcos.
PREDICTIONS
- Lunar occultations — Moon occulting stars and planets with sub-second contact times
- Planetary occultations — rare events where a planet occults a star
- Asteroid occultations — eight major asteroids tracked as occulters
- All predictions topocentric — corrected for your exact position and elevation
INSTRUMENTS
- Chronological event list with contact times, position angles, limb classification
- Polar sky plot — zenithal projection of tonight’s sky with body tracks
- Telescope viewfinder — animated event simulation with time scrubber
- Instrument readout panel — full immersion/emersion data for each event
COMPUTATION
- Meeus Ch.47 lunar ephemeris (ELP2000-82 series)
- VSOP87 truncated planetary positions
- Keplerian asteroid orbital elements
- 8,870 stars from ESA Hipparcos (public domain)
- Prediction window up to 5 years
- Background refresh keeps predictions current overnight
No internet required. No ads. No tracking. No subscription. Part of the Phosphor Suite.
SUPPORT
- Ask a question — help and guidance
- Report a bug — something not working
- Request a feature — suggestions
You can also browse existing issues to see if your question has been answered.