Starlink Satellite Visibility Estimator

How to calculate Starlink visibility?

Visibility depends on three primary factors: the satellite's orbital position relative to your location, the sun being between 6 and 18 degrees below the local horizon (Civil/Nautical Twilight), and the satellite itself being illuminated by the sun.

Formula: Visibility = (Elevation > Min_Alt) AND (Sun_Alt < -6°) AND (Sat_Illuminated = True)

Using the Estimator: an example

Example: A user in Austin, TX (Bortle 5) checking for passes on June 12th with a 25° minimum elevation.

Step-by-step calculation:

1. Retrieve latest TLE (Two-Line Element) orbital data for the selected batch.
2. Propagate the orbit to find intersections with the observer's horizon.
3. Cross-reference timestamps with local solar altitude to ensure twilight conditions.
4. Calculate predicted magnitude based on the phase angle of the sun and satellite distance.

Frequently Asked Questions

Why are they called trains?

Shortly after deployment, Starlink satellites are released in a dense cluster. Because they occupy similar orbital planes and are initially close together, they appear as a bright, linear "train" of lights until they raise their orbits to operational altitudes.

Can I see them in the city?

Visibility in urban areas depends on the magnitude threshold. While many passes are bright enough for Bortle 5 or 6 skies, heavy light pollution in city centers (Bortle 8-9) may require binoculars to see satellites clearly.

How often is data updated?

Orbital data is updated multiple times per day. The estimator pulls the latest TLE refresh rates directly from Space-Track to account for orbital maneuvers and atmospheric changes.