Star Index: Sky Forecast

One score for tonight's sky: clouds, humidity, wind, moon, twilight. Messier windows, meteor shower alerts, widgets. One-time Premium unlock, not a subscription.

Cloud, humidity, wind, moonlight and twilight, distilled into one number. Star Index tells you whether tonight is a go for stargazing, 0 to 100, before you drive anywhere.

STAR INDEX (0-100) Cloud cover is broken down by altitude layer and combined with humidity, wind speed, moon phase and twilight timing. Hourly and 7-day outlooks let you plan ahead. Seeing (atmospheric steadiness) and transparency are scored separately, so you can tell whether tonight favors planets or faint deep-sky targets.

DEEP-SKY CATALOG All 110 Messier objects plus major NGC targets, each with its best viewing window worked out from twilight end and moonrise/moonset for your location. Planet and moon rise/set times, direction and altitude at a glance.

NEVER MISS A SHOWER Get a viewing-conditions score for 8 major meteor showers (Quadrantids, Perseids, Geminids and more), with a push notification as the peak approaches. Eclipses and planetary oppositions are on a built-in calendar.

WIDGETS Home screen and Lock Screen widgets keep tonight's Star Index visible without opening the app.

ON-DEVICE AI (supported devices) On iOS 26 devices with on-device intelligence, Star Index writes a plain-language read of tonight's conditions. Unsupported devices fall back to a rule-based summary automatically.

PRIVATE Location is used only to forecast your local sky. No account, no data collection, no ads.

PREMIUM (one-time purchase, not a subscription) Unlock multiple saved locations, the full Messier catalog, photography windows and the 7-day outlook with a single purchase.

Stop guessing from a generic weather app. Star Index tells you if tonight is worth the drive.

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