Sky Tool
Interactive Star Chart
The dome of the sky for any date, time and place: bright fixed stars, the ecliptic and the four directions, in a zenith-centred stereographic projection.
- Centre: zenith, straight overhead
- Edge of circle: horizon
- Dashed line: ecliptic
- Orientation: north at the top, east on the left
Hover over a star, or tap it, to see its magnitude, altitude, azimuth and coordinates.
About This Tool
This tool is an interactive star chart that draws the sky as it appears at the date, time and geographic location you enter. It shows the bright fixed stars above the horizon, the ecliptic (the Sun's yearly path) and the four cardinal directions in a stereographic projection on a round dome. The centre of the circle is the zenith, the point straight above your head, and the outer edge is the horizon. You read the chart as if you were lying on your back looking up (north at the top, east on the left). Hover over a star, or tap it on a phone, to see its magnitude, altitude and azimuth, and its equatorial coordinates (RA/Dec).
The lights on the chart are not planets but the fixed stars of classical astronomy. First-magnitude stars such as Sirius, Aldebaran, Antares, Regulus, Spica and Vega are placed by their coordinates, so you can follow when a star rises, culminates (reaches its highest point) and sets. Positions are computed from local sidereal time (LST) and latitude, which is why the same moment gives a different sky in Istanbul and in another city.
In classical astrology the fixed stars have a place of their own. Ptolemy assigns each bright star the nature of one or two planets in the Tetrabiblos: Algol in Perseus is of Saturn and Jupiter, Aldebaran of Mars, Regulus of Mars and Jupiter, and Antares of Mars and Jupiter. When a fixed star comes into close angular contact with a planet or with an angle of the chart (ASC, MC), it brings that nature into the picture. In the traditional reading a star's influence is read not only through its zodiacal longitude but also through paranatellonta: a star rising or crossing the meridian at the same moment a planet stands on an angle links the two. Because this chart shows exactly those moments of rising, culmination and setting, it suits classical fixed star work.
Another key of the old tradition is the heliacal rising and setting: the moment a star, freed from the Sun's glare, first reappears on the horizon just before dawn. In Egypt the heliacal rising of Sirius announced the flooding of the Nile and the new year, and classical sources attach seasonal and prophetic meanings to these first appearances. Ptolemy's star catalogue in the Almagest lists 1022 stars in 48 constellations and for centuries formed the basis of both astronomy and the astrological doctrine of the fixed stars.
Finally, the position of the stars against the signs is not fixed. Because of precession (the slow wobble of the Earth's axis, the precession of the equinoxes), the fixed stars advance in zodiacal longitude by about 1° every 72 years, a full circle in about 25,800 years. A star that stood at the beginning of a sign in Ptolemy's day may therefore have moved into the next sign today. This tool keeps the star positions fixed at epoch J2000 and does not apply precession, so for dates centuries or millennia away from today the real positions of the stars drift away from the chart. Star positions and magnitudes are taken from the Yale Bright Star Catalogue (J2000). In short, this page is an honest sky-dome visualiser that makes no grand claims of prophecy: it shows the real motion of the fixed stars across the sky and gives you ground to explore the classical star tradition with your own eyes.
Frequently Asked Questions
What exactly does this star chart show?
It shows the sky as it looks for the date, time and place you enter: the bright fixed stars above the horizon, the ecliptic and the directions. The centre of the circle is your zenith and the edge is the horizon. It is not a birth chart or a planet table but a stereographic projection of the real dome of the sky.
Are the lights on the chart planets or fixed stars?
All of them are fixed stars. Bright stars such as Sirius, Aldebaran, Antares, Regulus, Spica, Vega and Betelgeuse are placed by their equatorial coordinates. The planets and the Moon move quickly across the sky, so they are not included; the chart focuses on the sphere of the fixed stars.
Do the fixed stars have a nature in classical astrology?
Yes. In the Tetrabiblos Ptolemy gives each bright star the nature of one or two planets: Algol is of Saturn and Jupiter, Aldebaran of Mars, Regulus of Mars and Jupiter, Antares of Mars and Jupiter. When a star comes into contact with a planet or an angle of the chart, it brings that nature into the reading.
What are heliacal rising and setting?
A star's heliacal rising is its first reappearance on the horizon just before dawn, after it has been hidden in the Sun's glare; its heliacal setting is its last evening sighting in the west. In Egypt the heliacal rising of Sirius marked the flooding of the Nile and the new year. The classical tradition attaches seasonal and prophetic meanings to these first appearances.
What does paranatellonta mean?
It is the condition of a fixed star and a planet standing on the angles of the sky at the same moment, for example one rising while the other culminates. In the traditional reading a star's influence is read not only through zodiacal longitude but also through this simultaneous rising, culmination and setting. Because this chart makes those moments visible, it suits paranatellonta work.
What is Ptolemy's star catalogue?
In his Almagest, Ptolemy lists 1022 stars in 48 constellations with their brightness (magnitude) and positions. For centuries this catalogue was the foundation of both astronomy and the astrological doctrine of the fixed stars, and later star lists largely depend on it.
How does precession affect star positions?
Because of precession, the slow wobble of the Earth's axis, the fixed stars advance in zodiacal longitude by about 1° every 72 years, and a full cycle takes about 25,800 years. A star at the start of a sign in Ptolemy's day may now stand in the next sign. This tool keeps star positions fixed at J2000 and does not apply precession, so for dates far from the present century the positions on the chart drift away from the real ones.
Why is the chart round, and what is Local Sidereal Time?
The circle is a stereographic projection of the dome of the sky above your head: the centre is the zenith and the edge is the horizon. Local Sidereal Time (LST) is an astronomical clock that shows which celestial longitude is crossing your meridian right now; it decides which stars are rising, culminating or setting. When you change the location, the LST changes and the sky turns accordingly.