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SpacePings vs ISS Detector
Both apps alert you before a pass. Here's the honest difference in what happens after that alert fires.
ISS Detector, by Derk Vrijdag, is closer in spirit to SpacePings than any web-based predictor: it's an app built to alert you, not a table you check. Its own description is direct about the job -- "ISS Detector will tell you when and where to look for the ISS. You get an alarm a few minutes before a pass. You will never miss it." A short audio cue sounds five seconds before a pass starts, a genuinely nice touch for someone already standing outside with their phone in a pocket. Its Globe and Star dome views, plus an augmented-reality camera mode, give you several honestly different ways to actually find the satellite once you're looking. For $0.99-$11.99 in one-time or subscription in-app purchases, that expands to Starlink trains, Hubble, rocket bodies, and even ham and weather satellites with real-time Doppler info -- a genuinely deep catalog for anyone past casual ISS-spotting.
| Feature | SpacePings | ISS Detector |
|---|---|---|
| Push notification before a pass | Yes -- free tier, one push per pass that clears the quality gate (30°+ peak elevation, dark enough sky, forecast clear enough) | Yes -- "an alarm a few minutes before a pass," plus a short audio cue 5 seconds before the pass begins |
| Calls the exact Fade / ignition moment | Yes -- a live countdown to the second the satellite crosses into Earth's shadow, plus a haptic buzz 10 seconds out | Not described -- its alarm and audio cue time the pass start, not a shadow-crossing moment; the app's own listing makes no mention of the satellite fading or eclipsing mid-pass |
| Weather awareness | Cloud-gated -- a pass alert only fires if the forecast cloud cover for that hour is under 40% | Checks and shows conditions alongside the alarm ("will also check if the weather conditions are right") |
| Aiming help | A compass arrow and an elevation tilt arc, both spoken aloud for VoiceOver | Globe view, Star dome view, an augmented-reality camera overlay, and manual compass calibration |
| Satellite catalog | ISS, Starlink trains, other bright naked-eye passes, plus launches worth watching | ISS free; Starlink trains, Hubble, rocket bodies, ham/weather satellites, comets, and planets behind in-app purchases ($0.99-$11.99) |
| Platform & price | Native iOS app; free tier, Pro $4.99/mo or $29.99/yr | iOS and Android; free with in-app purchases ($0.99-$11.99) |
Where the two apps diverge is what the alert is for. ISS Detector's alarm and audio cue are timed to the pass itself -- a heads-up minutes before it starts, then a cue five seconds out. Nothing in its own description mentions the one thing that makes some passes stop cold, mid-sky, with no horizon in sight: the satellite flying out of the Sun and into Earth's own shadow. SpacePings' countdown is built around that specific instant -- calling the fade or ignition to within about ten seconds of the real event, with a haptic buzz ten seconds before it happens, on top of a push that only ever fires for passes the quality gate actually clears (a dark enough sky, a bright enough satellite, and a forecast clear enough to actually see it -- for SpacePings a hard gate on whether the push fires at all).
Both are real, useful tools built by people who clearly care about getting this right. If you want the deepest catalog and the most ways to visually locate a satellite once it's up, ISS Detector's years of steady updates show. If you want one push that's already decided tonight is worth it, and a call at the exact second the sky does something worth watching for, that's what SpacePings pings for -- free on iOS, no account needed to check tonight's sky.