The ISS satellite pass timer explains when and how to see the International Space Station. The ISS appears as a brilliant moving "star" crossing the sky in 3–6 minutes. It's the brightest man-made object in the night sky, reaching magnitude -6 at maximum brightness.
ISS Orbital Facts
For exact pass times, use Heavens-Above.com — enter your latitude/longitude for precise predictions showing direction, elevation, and visibility duration for each pass.
Visibility Window Calculator
The ISS is only visible when it's illuminated by the Sun while you're in darkness. Enter your local sunset/sunrise times to estimate visible pass windows.
How to Spot the ISS
Check Pass Time
Get the exact pass time from Heavens-Above or NASA's Spot the Station app. Note the start direction (compass bearing).
Find the Direction
Go outside 2 minutes early. Face the compass direction listed. No binoculars needed — it's visible to the naked eye. A clear sky with no clouds is ideal.
Watch It Cross
The ISS appears as a fast, steady, very bright dot — no blinking unlike aircraft. It crosses the sky in 3–6 minutes. Wave if you want.
Other Bright Satellites
| Satellite | Altitude | Period | Max Brightness | Notes |
|---|---|---|---|---|
| ISS | 420 km | 92 min | -6 mag | Largest man-made object in orbit |
| Tiangong | ~380 km | 91 min | -2 mag | Chinese space station |
| Starlink train | 550 km | 97 min | 3–5 mag | String of dots, visible after launch |
| Iridium flares | 780 km | 100 min | -8 mag | Older Iridium sats with antenna flares |
How to Use the Satellite Pass Timer
This guide explains the science behind ISS visibility and helps you understand the visibility windows for your location. For precise pass times with exact trajectory and elevation, use Heavens-Above.com — it is the most accurate free satellite tracking tool available.
Why the ISS Is Only Visible at Certain Times
The ISS shines by reflected sunlight. For it to be visible, two conditions must be met simultaneously: the ISS must be in sunlight (not in Earth's shadow), and your location must be in darkness (nighttime). These conditions typically align in the hour or two after sunset and before sunrise. At local midnight, the ISS is often in Earth's shadow and invisible.
Photographing the ISS
For a long-exposure trail: set up a tripod with a wide-angle lens (16–24mm), open to f/2.8, ISO 400, and expose for 15–30 seconds during the pass. The ISS will appear as a bright streak through your image. Check the pass trajectory beforehand to frame a compelling foreground — a mountain, cityscape, or lone tree makes for a dramatic composition.
For resolved images showing the station's structure: you need a telescope with motorized equatorial tracking, a camera capable of fast shutter speeds, and excellent seeing conditions. Dedicated ISS photographers use 300–400mm telescopes and manual tracking to capture the station's cross-shaped solar panels in detail.
FAQ
When is the ISS visible from my location?
The ISS is visible when it's in sunlight and your location is in darkness — typically 1–2 hours after sunset or before sunrise. It's not visible when the Sun is high in the sky because daylight washes it out. Passes occur several times per day, but only some passes are visible from any given location. Use Heavens-Above.com with your coordinates for precise pass times.
How bright is the ISS?
The ISS can reach magnitude -6 at its brightest — much brighter than Venus. On an average visible pass it appears around magnitude -1 to -3. It looks like a very bright star moving steadily across the sky, typically taking 3–6 minutes to cross from horizon to horizon. It never blinks, which distinguishes it from aircraft.
How fast does the ISS move?
The ISS orbits Earth at about 7.7 km/s (17,500 mph) at an altitude of roughly 420 km. It completes one orbit every 92 minutes. Due to Earth's rotation, it passes over your location from different directions each orbit, and not every orbit is visible.
Can I photograph the ISS?
Yes. For a long trail shot, use a 10–30 second exposure on a static tripod with a wide-angle lens at f/2.8, ISO 400–800. You'll capture the ISS as a bright streak across the sky. For a resolved image showing the structure, you need a telescope with tracking and fast shutter speeds (1/500s+).
Is this tool free?
Yes, completely free. For precise pass predictions with exact times and trajectories, visit Heavens-Above.com — it's the gold standard for satellite tracking.