How this is computed
There is no sky database behind this page and no feed scraped from another site. When the page opens, your browser does the astronomy itself:
- Sun and twilight. Solar position from the standard low-precision solar theory (the same family of math as NOAA’s solar calculator); sunset and sunrise are the sun’s center at −0.833°, and twilight ends at −6°, −12°, and −18°. Spot-checks against published tables run within about a minute.
- Moon. Lunar position with the major perturbation terms after Paul Schlyter’s “How to compute planetary positions,” phase from the sun–moon geometry, rise and set by scanning the actual computed altitude — the same ephemeris family validated against U.S. Naval Observatory values on our sister sites.
- Planets. Heliocentric elements after Schlyter, with the published perturbation terms for Jupiter, Saturn, and Uranus; brightness from Mallama & Hilton (2018), the current standard magnitude system. A planet is called visible only if it is up while the sky is dark and far enough from the sun — otherwise the table says so and says why.
- The station. ISS passes are propagated with SGP4 from two-line elements published by CelesTrak. A pass counts as visible only when the station is sunlit, your sky is dark, and it climbs at least 10°. The elements’ date is printed in the ISS section; elements older than ten days are refused rather than shown stale.
- Meteors. Shower dates, peak nights, radiant positions, and ZHR (zenithal hourly rate — the ideal dark-sky rate) are the standard published values; the page computes the radiant’s height for your place and the moon’s interference honestly, including when the answer is “not tonight.”
The fine print, in ordinary size
Pass and meteor-shower predictions are estimates for recreational viewing only — not for navigation, aviation, or any operational use. Everything here is computed for general information and planning only. Times are estimates: solar and lunar times can differ from official tables by a minute or two, pass predictions drift as orbital elements age, and meteor rates vary from year to year. Weather, terrain, light pollution, and your local horizon decide what you actually see. Do not use this site for navigation, aviation, timing anything safety-critical, or any operational purpose.
Built in Alaska as part of a small fleet of public-data sites. The astronomy is free knowledge; the layout is ours.