Why these factors matter / sources
Visibility requires a dark observer while the spacecraft is still sunlit. A high elevation generally gives a shorter atmospheric path and makes aiming easier; this console starts with a 60° peak target and lets you narrow to 75° overhead. Satellite altitude is only one factor: altitude helps distinguish low orbit from higher orbit, but it does not tell us how bright the spacecraft looks from the ground.
Brightness also changes with observer distance, projected area, solar phase angle, material reflectance, shadowing, and spacecraft attitude. Large stations are often easier targets; Starlink brightness varies by generation, operating mode, panel orientation, and phase. Public orbit catalogs do not provide reliable visual magnitudes or current attitude, so the score below is a relative observing-conditions index, not a chance percentage.
The relative index favors high passes, an illuminated spacecraft, clear forecast, smaller Moon interference, fresher elements, and lower historical light at the pin. It is a sorting aid, not a probability or satellite brightness measurement. Cloud forecasts cannot see every local haze or cloud patch. Open-Meteo cloud and visibility values are forecasts, not a local all-sky camera.
NASA’s daily VIIRS layer is a recent nighttime radiance observation, not a clean measurement of skyglow: clouds, moonlight, snow, fires, and gaps can affect it. The separate persistent-light view is the 2016 Black Marble baseline, useful for broad comparison but too old to treat as current. Dark-site search samples that baseline and ranks lower pixels nearby, then checks cloud and precipitation forecast for the short list. It cannot verify a safe legal place to stand.
Mapbox receives address searches; Open-Meteo receives coordinates to return weather and model terrain elevation. Coordinates remain in this page session. Observation outcomes are stored only in this browser until you export or clear them. The sound cue requires this page to stay visible and focused; mobile browsers can suspend it when the screen locks.
Use public roads and legal observing locations. The map’s dark-area search does not confirm public access, parking, terrain, nearby trees, or local safety. Orbital predictions use TLE/OMM element sets and SGP4; they are not satellite telemetry. Satellite altitude, range, sunlit fraction, and sky path are propagated from catalog elements. Actual brightness depends on size, shape, surface, solar angle, attitude, rotation, and distance, which public catalogs generally do not report. Compare a sighting with the exact predicted time, direction, elevation, and element epoch before calling a pass calibrated. Save both successful and failed observations so the field record can expose timing or identification bias.