Predict exactly when the ISS, Tiangong, Hubble and other satellites will cross the face of the Sun or Moon from your location. Live transit corridor maps, photography guides, countdown timers and historical data — computed hourly using precision orbital mechanics.
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Solar safety warning: NEVER look at the Sun without a certified solar filter (ISO 12312-2). Observing or photographing a solar transit without proper eye protection will cause permanent eye damage or blindness. Suitable filters include Baader AstroSolar Safety Film (ND 5.0), Thousand Oaks Solarlite, or dedicated solar telescope filters. Regular sunglasses, camera ND filters and smoked glass are NOT safe. Lunar transits do not require any filter.
—Transits found
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Maximum travel distance
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☀ SOLAR TRANSIT
Next transit from your location
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Upcoming Transits 0
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Satellites that pass close to the Sun or Moon but don't cross the disc from your location. The corridor may be reachable by travelling to a nearby position.
🔔 Transit Alerts
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Get notified by email when a satellite transit is predicted near your location. We check daily and send alerts ahead of each transit so you have time to prepare your equipment and travel to the corridor.
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🗺️ Transit Corridor Map
The shaded band shows the narrow visibility corridor — typically only 5–10 km wide. To see the satellite cross the Sun or Moon, you must be standing within this corridor. The blue pin shows your current position. Click anywhere on the map to check distance from the centreline, or click a point inside the corridor for driving directions.
Map view:
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Select a transit above to view its ground corridor on the map
📐 Transit Geometry — Why Transits Are So Rare and Brief
A satellite transit occurs when a satellite passes directly between you and the Sun or Moon. Because the ISS orbits only ~420 km above Earth — while the Sun is 150 million km away — the "shadow corridor" projected onto Earth's surface is extremely narrow. You must stand within this corridor to witness the transit, and it typically lasts less than two seconds.
~0.53°
Angular diameter of the Sun and Moon (nearly identical — which is why solar eclipses work)
~50″
ISS angular size at 420 km — about 2.6% of the solar/lunar disc diameter
0.3–1.5 s
Typical transit duration — the ISS crosses the disc at 7.7 km/s (28,000 km/h)
5–10 km
Transit corridor width on the ground — you must be inside this strip
🌙 Current Moon Phase
Moon phase affects lunar transit visibility and photography settings. A brighter Moon makes it easier to capture the transit silhouette.
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☀️ How to Photograph an ISS Solar Transit
An ISS solar transit is one of the most spectacular images in amateur astronomy — the detailed silhouette of the space station crossing the face of our star. Capturing it requires precise timing, the right equipment, and absolute adherence to solar safety. Here is everything you need to know.
Essential Equipment
⚠️ Solar Filter (MANDATORY)
Full-aperture front filter: Baader AstroSolar Safety Film (ND 5.0), Thousand Oaks Solarlite, or dedicated manufacturer filter. Must cover the ENTIRE front of the telescope. NEVER use eyepiece-end filters — they can crack from heat. Alternatively, use an H-alpha solar telescope (e.g. Coronado PST, Lunt LS60) for chromosphere views.
🔭 Telescope
Refractor 80–120 mm f/6–f/8 for sharp, high-contrast images. Schmidt-Cassegrain (SCT) 6–8" works well for longer focal length. Avoid Newtonians for solar work (secondary mirror obstruction reduces contrast).
📷 Camera
DSLR or mirrorless with high-speed burst mode (10+ fps). Dedicated astronomy cameras (ZWO ASI, QHY) can capture video at 120+ fps for maximum frame coverage. Camera must support 1/1000 s or faster shutter.
⏱️ GPS Clock
GPS time-sync app (e.g. Emerald Time, GPS Clock Sync) for sub-second accuracy. The transit lasts <2 seconds — you need to start shooting at exactly the right moment. Sync your camera clock to GPS before the session.
Recommended Camera Settings
Setting
White-Light Solar Filter
H-Alpha Telescope
Shutter Speed
1/1000 s – 1/2000 s
1/500 s – 1/1000 s
ISO
100–400
200–800
Aperture
Native (telescope)
Native (telescope)
Mode
High-speed burst / video
Video at highest fps
Focus
Manual — focus on sunspots or solar limb
Manual — focus on prominences
Step-by-Step Process
1. Check the prediction: Use the transit predictor above to find an upcoming solar transit. Note the exact UTC time, the transit corridor centreline, and the corridor width. Plan to be at a location on or very near the centreline.
2. Set up early: Arrive at least 30 minutes before the transit. Attach the solar filter to the front of your telescope BEFORE pointing at the Sun. Focus on sunspots or the solar limb. Frame the full solar disc with some margin.
3. Synchronise your clock: Open a GPS time app on your phone. Verify your camera's clock matches GPS time. Set a timer alarm for 10 seconds before the predicted transit time.
4. Capture: Start shooting in continuous burst mode 3–5 seconds before the predicted time. Keep shooting until 3–5 seconds after. At 10+ fps, you will capture 60–100 frames in a 10-second window — plenty to catch the 0.5–1.5 second transit.
5. Process: Review your frames to find those showing the ISS silhouette against the solar disc. Stack multiple transit frames to create a composite image showing the ISS path across the Sun. Adjust levels and sharpen to enhance the silhouette detail — you should be able to resolve solar panels, the truss structure, and docked spacecraft.
🌙 How to Photograph an ISS Lunar Transit
Lunar transits are more accessible than solar transits because they require no solar filter — making them an excellent entry point for astrophotographers. The ISS silhouette against the cratered lunar surface is equally striking, and the absence of filter requirements means you can capture the transit with simpler equipment.
Key Differences from Solar Transits
✅ No Filter Required
Unlike solar transits, lunar transits are completely safe to observe without any filter. You can look through the telescope eyepiece directly. This makes setup faster and removes the most dangerous step.
🌓 Moon Phase Matters
A gibbous or full Moon (>70% illumination) provides the best contrast for the ISS silhouette and allows faster shutter speeds. A crescent Moon requires higher ISO and careful exposure to avoid noise.
🌃 Can Occur at Night
Lunar transits can happen any time the Moon is above the horizon — including deep at night. The Moon does not need to be near the horizon. Some of the best lunar transits occur with the Moon high in a dark sky.
💡 ISS May Be Lit
If the transit occurs when the ISS is sunlit (the ISS passes into shadow when the Sun is >30° below the horizon), the station may appear bright against the darker lunar mare regions, rather than a pure silhouette.
Camera Settings by Moon Phase
Moon Phase
Shutter Speed
ISO
Notes
Full Moon (90–100%)
1/1000 – 1/2000 s
200–800
Best contrast, easiest to capture
Gibbous (60–90%)
1/500 – 1/1000 s
400–1600
Excellent for detail in both lit and shadow regions
Quarter (40–60%)
1/250 – 1/500 s
800–2000
Good contrast along the terminator
Crescent (10–40%)
1/125 – 1/500 s
800–3200
Lower contrast — try to catch ISS crossing the lit crescent
🔭 Recommended Equipment for Transit Photography
Transit photography demands specific capabilities: fast shutter speeds, long focal lengths, and (for solar work) certified filtration. Here are the categories of equipment that work best, from beginner-friendly to advanced.
Telescopes
Beginner: 80 mm Refractor
Focal length ~480–600 mm. Affordable, portable, sharp. Ideal first telescope for transit work. Pair with a 2× Barlow to reach ~1000 mm effective focal length.
Intermediate: 6" SCT (f/10)
1500 mm focal length natively. Compact, well-corrected, good for resolving ISS solar panel structure. Excellent all-round planetary and transit scope.
Advanced: 8" SCT or 120 mm APO
2000 mm focal length. Resolves fine ISS structural detail. Requires sturdy mount. The 120 mm APO refractor produces the sharpest images but is expensive.
Solar Filters
Baader AstroSolar Safety Film
ND 5.0 (visual) or ND 3.8 (photographic). Sheet film you cut and mount yourself in a cardboard or 3D-printed cell. Very affordable, optically excellent. The most popular choice among transit photographers.
Thousand Oaks Solarlite
Glass filter in an aluminium cell sized for your telescope. More durable than film. Available in standard sizes from 50 mm to 200 mm+.
H-Alpha Telescopes
Dedicated solar scopes (Coronado PST, Lunt LS60/LS80) show prominences and chromospheric detail. More expensive but produce stunning images. Slower effective aperture requires adjusted camera settings.
❓ Frequently Asked Questions
Can you predict ISS transits of the Sun and Moon?▼
Yes. Using precise TLE (Two-Line Element) orbital data and SGP4 propagation, combined with solar and lunar ephemeris calculations, Orbital Radar predicts exactly when and where the ISS (or any tracked satellite) will appear to cross the disc of the Sun or Moon as seen from a specific location on Earth. These transits are extremely location-specific — the visibility corridor is typically only 5–10 km wide, so predictions must be computed for your exact coordinates. Our engine computes predictions for 14 days ahead, updated hourly.
How rare are ISS solar transits?▼
For any given location, an ISS solar transit typically occurs a few times per year — but the exact frequency depends on your latitude and how the ISS orbit aligns with the Sun's position. Because the transit corridor is only about 5–10 km wide, you often need to travel a short distance to reach the centreline. Globally, ISS solar transits happen somewhere on Earth several times per day.
How long does an ISS transit last?▼
A typical ISS solar or lunar transit lasts between 0.3 and 1.5 seconds. The ISS travels at approximately 7.7 km/s (28,000 km/h), and the Sun and Moon each subtend about 0.5° in the sky. At the ISS orbital altitude of ~420 km, this translates to a very brief crossing.
Do I need a telescope?▼
A telescope or long telephoto lens (1000 mm+) is strongly recommended to resolve the ISS silhouette against the disc. At 50 arcseconds, the ISS is too small to see detail with the naked eye against the disc. For solar transits, a certified solar filter is also essential.
Can other satellites transit the Sun or Moon?▼
Yes. Any satellite large enough to be resolved can produce a transit. Orbital Radar predicts transits for the ISS (109 m), China's Tiangong space station (30 m), the Hubble Space Telescope (13.2 m), and other large objects like Envisat (26 m). Smaller satellites can also transit but appear as tiny dots requiring larger apertures.
How wide is the transit corridor?▼
The transit visibility corridor is typically 5–10 km wide on the ground. This is because the ISS is relatively close to Earth (~420 km altitude), so the geometric "shadow" it casts against the distant Sun or Moon is very narrow. To see the transit, you must be positioned within this corridor. The corridor centreline and width are shown on the interactive map for each predicted transit.
Is it safe to watch a solar transit without a filter?▼
No — NEVER. You MUST use a certified solar filter (ISO 12312-2) to observe any solar transit. Looking at the Sun without proper protection — even briefly — causes permanent eye damage or blindness. Lunar transits are completely safe to observe without any filter.
What is the best time to photograph a transit?▼
Solar transits can only occur during daytime when the Sun is above the horizon. The higher the Sun's elevation, the less atmospheric distortion and the sharper the ISS silhouette. Lunar transits can occur any time the Moon is up — nighttime transits often produce the cleanest images because the darker sky improves contrast. Elevation above 30° is ideal for both.