Place, time and the observing window
City presets are approximate city-center coordinates, not a location service. Custom latitude and longitude accept decimal degrees; north and east are positive. Calculations assume sea level and an unobstructed, level horizon. Elevation, mountains, buildings and trees are not modeled.
Each plan starts at noon on your selected date in the selected IANA time zone and ends at the following local noon. This keeps one evening and its following morning together. The browser’s time-zone database handles daylight-saving changes. A window can therefore be 23, 24 or 25 elapsed hours. Choose the correct display zone for custom coordinates; coordinates do not automatically identify a legal time zone.
Dates from 2000 through 2100 are accepted for educational planning. Displayed times are rounded to minutes. Avoid treating this as a precision ephemeris, and independently check critical event timings.
Sun, Moon and darkness
Solar/lunar position and Moon illumination use SunCalc 1.9.0, an MIT-licensed library by Vladimir Agafonkin. It implements compact approximate astronomical formulas. Sunrise and sunset use a solar-center altitude of −0.833° to approximate the Sun’s radius and standard horizon refraction.
Astronomical darkness means solar altitude below −18°. “Dark + Moon down” also requires the SunCalc lunar-center altitude, including its approximate refraction correction, below 0°. This is not a precise upper-limb moonrise/set convention and does not explicitly correct for local observer parallax or lunar radius. Moonrise/set and lunar altitude can differ from a high-precision topocentric ephemeris, particularly near the horizon. Use them as planning estimates, allowing several minutes of margin, and more at high latitudes or grazing crossings. No fixed error bound is claimed.
Transitions are bracketed at one-minute intervals and numerically refined within those brackets. A sub-minute grazing interval can be missed. Chart points are sampled every five minutes; the line is a visual guide, and altitudes below −45° are clipped. The time scrubber computes a fresh position at its selected instant.
The Moon phase and illuminated fraction are evaluated halfway through the observing window. The disk diagram is schematic and is not rotated to match the local sky. The green window is geometric, not a forecast of sky brightness, cloud, transparency, seeing, aurora or target visibility.
Station data and pass calculations
Bundled orbital snapshot retrieved 10 November 2026 at 09:49:09 UTC. Source: CelesTrak; underlying basic space situational awareness data credited to USSPACECOM / Space-Track.org. Only ISS (NORAD 25544) and Tiangong’s core station object (NORAD 48274) are included.
The SGP4 implementation is satellite.js 6.0.1, MIT-licensed. Pass computation runs in a local Web Worker. It considers geometric passes above 10°, finds each peak, and samples lighting at 10-second steps. A spherical-Earth, cylindrical-shadow approximation determines sunlight. Penumbra, station brightness, attitude, weather, local obstructions and maneuvers are omitted.
Every point of a requested window must fall within seven days of an object’s element epoch; otherwise that object is skipped. The station worker supports at most 24 elapsed hours, so on a 25-hour daylight-saving transition it omits the final hour. The station status explicitly states its checked duration. Passes clipped at a window boundary are marked. Up to twelve matching cards are shown.
There is no automatic network refresh and no live telemetry. A stale snapshot disables the optional pass tool for current dates. The publisher must deliberately retrieve and validate replacement elements. Do not use these results for navigation, safety, collision avoidance or mission operations.
Photography, illustrations and licenses
The homepage’s orbital photograph is Milky Way on the Horizon, captured by NASA astronaut Don Pettit on 29 January 2025. Credit: NASA / Don Pettit. It is a long-exposure view from orbit, not a realistic simulation of what the naked eye will see from your location. It has been resized and cropped for layout.
The Moon photograph is FullMoon2010.jpg by Gregory H. Revera, taken on 22 October 2010 from Madison, Alabama. It is licensed under Creative Commons Attribution–ShareAlike 3.0, which permits commercial reuse with attribution and share-alike conditions. The locally hosted file is a resized Wikimedia thumbnail with no other changes and remains under that license. It is a reference photograph, not tonight’s phase. The orbital NASA photograph is used editorially under NASA’s media usage guidelines; no endorsement is implied.
The twilight and satellite illustrations are original vector artwork made for this site. They are explanatory diagrams, not measured trajectories. Bundled code license texts: SunCalc and satellite.js.
Methodology and editorial review: 10 November 2026. This independent project has no affiliation with NASA, CelesTrak or station operators.