Free ISS Tracker Comparison
Geometry apps predict when the station is sunlit. Weather still decides if you see it.
ISS Pass Predictor · Is the ISS Visible Tonight?
Options
| Tool | Best at | Tradeoff | |------|---------|----------| | NASA Spot the Station | Email/text alerts, trusted | Less interactive exploration | | Heavens-Above | Deep pass tables | Denser UI; account habits vary | | AstroPhotosGY ISS Passes | Free browser, visibility flags, lat/lon links, Learn path | Not an email alert service |
Practical combo
Many observers keep Spot the Station alerts, then open a browser table the afternoon of a pass. Add Tonight Score so you do not wait under a solid deck of cloud for a faint pass.