Education / Astronomy
Star Map: A Planisphere for Your Location and Time
Show the sky above a location's horizon at a chosen UTC date and time. Rotate and zoom the chart, filter stars down to magnitude 5, and tap a star to see its catalogue name and magnitude.
Star Map: A Planisphere for Your Location and Time: Projects stars above the horizon into a circular planisphere. The Sun, Moon and seven planets are calculated for the observer's location and time. North starts at the top and east at the left, as when looking upward. The map is educational, with about 1° precision; terrain, refraction, proper motion and light pollution are omitted. If the star catalogue is absent, the chart identifies that and still shows calculated bodies. Runs 100% locally in your browser with zero server file uploads.
- Category
- School & study tools
- Runs
- In your browser
- Cost
- Free · no sign-up
- Availability
- Ready to use
Runs entirely in your browser
0 catalogue stars above the horizon at this magnitude.
Tap a star or planet to inspect it.
Educational chart, about 1° precision. Azimuth runs clockwise from north. The horizon chart looks upward, so east is on the left. Stars use J2000 catalogue positions precessed to the date; proper motion, terrain, atmospheric refraction and light pollution are omitted. Constellation figures and boundaries are not shown. Use dates from 1900 to 2100.
Star catalogue
Hoffleit and Warren, The Bright Star Catalog, fifth revised edition (preliminary), 1991. Public-domain catalogue via NASA/HEASARC: https://heasarc.gsfc.nasa.gov/W3Browse/star-catalog/bsc5p.html . The bundled subset includes visual magnitudes ≤ 5 and J2000 equatorial positions.
Position calculations
Astronomy Engine by Don Cross, MIT licence: https://github.com/cosinekitty/astronomy . Planet positions use its VSOP-based models; its lunar model and coordinate transforms supply the Moon, precession and observer corrections. Greenwich mean sidereal time follows the standard polynomial in Jean Meeus, Astronomical Algorithms, chapter 12.
How to use it
- Enter latitude, east-positive longitude and a UTC date and time, or request browser geolocation.
- Rotate or zoom the chart and choose the faintest star magnitude.
- Tap a visible star, Sun, Moon or planet, or use the star list and body table.
Privacy & limitations
All sky calculations use bundled data in your browser. Geolocation is requested only when you press Use my location; coordinates are not uploaded.
Related tools
Frequently asked questions
Which stars are included?
The Yale Bright Star Catalogue, fifth edition, supplies J2000 positions and visual magnitudes at or brighter than magnitude 5. Catalogue designations are shown when a familiar name is unavailable.
Why is east on the left?
A sky map represents the view looking up. With north at the top, east lies to the left. Rotation changes the chart's orientation; the compass labels rotate with it.
How accurate are the positions?
The chart is for learning and finding broad directions, about 1° precision. Stars are precessed to the chosen date. The Sun, Moon and planets use Astronomy Engine, with observer parallax and date-based coordinates. Geometric altitude is shown without atmospheric refraction.
Are constellation figures shown?
No constellation stick figures or boundaries are included. Star patterns differ between traditions, and this chart does not draw them.
Can I view the daytime sky?
Yes. A notice appears when the Sun is above the horizon. The chart still plots geometric star positions, although most stars are invisible in daylight. Supported dates run from 1900 to 2100.
Free tool · runs in your browser · no account required