How Transit Chaser Works
Transit Chaser is a browser-based tool that watches live aircraft data and checks whether any aircraft may line up with the Sun or Moon from your location.
The idea is simple: you keep your camera ready, and Transit Chaser watches the aircraft.
Your location matters
Aircraft transits are very location-specific. A plane can cross the Moon from one street and completely miss it from another. That is why Transit Chaser needs your observing location.
You can use automatic GPS location or enter your location manually. The more accurate your location is, the better the prediction can be.
Sun and Moon position
The app calculates where the Sun or Moon appears in the sky from your location. This includes the object’s altitude and azimuth. In simple terms, altitude is how high it is above the horizon, and azimuth is the compass direction.
Once the app knows where the Sun or Moon is, it can compare that position with nearby aircraft.
Live aircraft data
Transit Chaser uses live aircraft position data from third-party ADS-B style sources. These services provide information such as aircraft position, altitude, speed, heading, and sometimes aircraft type or callsign.
This data is useful, but it is not perfect. Aircraft positions may be delayed, missing, or updated at different intervals. Some aircraft may not appear at all depending on coverage, receiver availability, or data source limits.
Detection margin
The detection margin controls how close an aircraft needs to appear to the Sun or Moon before Transit Chaser alerts you.
A smaller margin is stricter. This is better when you only want serious photography alerts. A larger margin is more forgiving and may give more warnings, but some of them will be near misses.
There is no perfect setting for every situation. If you are using a very long lens or telescope, you may want a stricter margin. If you are still testing or want more warning, a slightly wider margin can help.
Prediction time
Transit Chaser can also look ahead by a short amount of time. This helps warn you when an aircraft may line up soon, not just when it is already close.
Longer prediction times can be useful, but they are also less certain. A plane can turn, climb, descend, or change speed. That is why an alert may appear and then disappear.
Why it is not guaranteed
Transit Chaser is a prediction tool, not a guarantee machine. The sky is real-time. Aircraft move. Data changes. Your location, timing, lens, and reaction speed all matter.
The app is designed to improve your chances and give you a heads-up. It does not replace common sense, safe solar practice, or proper planning.
Other modes
Transit Chaser also includes modes for plane watching, plane-on-plane events, and contrails. These modes are still based on the same idea: use aircraft data and your location to find interesting sky events.
Some modes are more experimental than others, but the goal is the same — help photographers notice opportunities they might otherwise miss.
In plain English
Transit Chaser checks where you are, where the Sun or Moon is, where nearby aircraft are, and whether anything is lining up. If something looks close enough, it alerts you.
You still need to be ready with the camera. The app just helps with the waiting and watching part.