Satellite Visibility Calculator
Calculate satellite visibility windows, maximum elevation angles, and pass duration for any location on Earth. Ideal for ISS spotting and satellite observation planning.
Observer Location
Satellite Parameters
Time Settings
Understanding Satellite Visibility
When Can You See Satellites?
Satellites are visible when:
- The satellite is in sunlight (not in Earth's shadow)
- The observer is in darkness or twilight
- The satellite is above the minimum elevation angle
- The sky is clear
Best Viewing Times
Satellites are most visible during:
- Dawn: ~1-2 hours before sunrise
- Dusk: ~1-2 hours after sunset
- When the observer is in shadow but satellite is sunlit
Elevation Angles
- 0°: Horizon level
- 30°: One-third up from horizon
- 45°: Halfway to zenith
- 90°: Directly overhead (zenith)
Orbital Characteristics
| Satellite | Altitude (km) | Inclination (°) | Period (min) | Visibility |
|---|---|---|---|---|
| ISS | ~408 | 51.6 | ~93 | Very bright, slow |
| Hubble Space Telescope | ~535 | 28.5 | ~96 | Bright, moderate speed |
| Starlink | ~550 | 53.0 | ~96 | Medium brightness |
| Iridium | ~780 | 86.4 | ~100 | Flares very bright |
| Geostationary | 35,786 | 0 | 1440 | Stationary, faint |
Satellite Magnitude Scale
- -8 to -4: Very bright (ISS, Iridium flares)
- -4 to 0: Bright (easily visible)
- 0 to +3: Moderate (good conditions needed)
- +3 to +6: Faint (dark skies required)
Factors Affecting Visibility
- Satellite size: Larger satellites appear brighter
- Solar panels: Can cause flares when properly oriented
- Atmospheric conditions: Humidity and pollution reduce visibility
- Light pollution: Urban areas make faint satellites harder to see
- Phase angle: Angle between Sun, satellite, and observer
Tracking Tips
- Use red light to preserve night vision
- Look for steady, moving "stars"
- Satellites don't blink (unlike aircraft)
- Motion is typically west to east
- Check multiple websites for accurate predictions