Free stargazing tool
Tonight's Sky
The real sky tonight: the constellation the moon is in, its phase, and the constellations overhead right now.
Waning crescent
Tropical moon sign (astrology): Leo
Computed for August 12. With JavaScript on, this updates to your current moment and adds where to look.
Constellations above you right now
Based on your time zone alone so directions are approximate.
The Big Dipper, in Ursa Major
Orion
Cassiopeia
high in the northeastern sky · look for Schedar
Cygnus, the Northern Cross
nearly overhead · look for Deneb
Lyra
high in the western sky · look for Vega
Scorpius
Taurus
Gemini
Leo
Boötes
Pegasus
Sagittarius
Carina
Crux
Grus
If you share your location it stays on this device — rounded to about 7 miles, used only by this page's math in your browser, remembered only in this browser, and never sent to us or anyone else.
How this page reads the sky
The moon phase above is computed. The page counts forward from a reference new moon through the 29.53-day lunar cycle, a mean-cycle model that tracks the true phase to under a day, which gives the phase name, the share of the disc that is lit, and the day of the lunar month.
Which constellation the moon is in is a separate calculation, because it is a separate question: phase is the angle between the sun, the earth and the moon, while the constellation is a direction, and the two run on different clocks a little over two days apart. So the page works out the moon's real position from the periodic terms of its orbit, then looks that position up against the boundaries the IAU adopted in 1930. Those boundaries are drawn for the sky as it stood in 1875, and precession has shifted everything about 1.75 degrees since, so the position is wound back to 1875 before the lookup. Skip that step and the answer is wrong every time the moon sits near a border, which is most of the time.
The constellations are placed with sidereal time, the clock astronomers use to track which stars have rotated into view. Your time zone gives a rough position on Earth; from there the page ranks fifteen well-known constellations, from Orion and the Big Dipper to Crux in the deep southern sky, and shows the three best placed right now. The moon gets the same treatment, so the panel says which way to look for it too. Share your location and the compass directions sharpen to your spot, along with the time each figure sets tonight and the time the moon does.
Everything drawn here is real. Star positions come from astronomical catalogs, the stick figures match the shapes printed on star charts, and southern-hemisphere visitors see every figure turned 180 degrees. Come back tomorrow night and it will have shifted: the stars rise about four minutes earlier each evening, and the moon moves one day further through its cycle.
Questions
- Which constellations are above me right now?
- This page ranks fifteen well-known constellations, from Orion and the Big Dipper to Crux in the deep southern sky, and features the three best placed right now. Each card gives a compass direction and names a bright star to look for, such as Vega. The default directions come from your time zone alone, so they are approximate; sharing your location sharpens them and adds the time each figure sets tonight.
- What constellation is the moon in right now?
- The moon panel names it. The page computes the moon’s position and looks it up against the official IAU constellation boundaries, so the answer names the constellation the moon sits in front of rather than the nearest zodiac sign. It changes every two or three days as the moon travels about 13 degrees a night, and it regularly falls outside the twelve zodiac constellations altogether, into Ophiuchus, Auriga, Sextans, Cetus or Orion. Alongside it the panel gives the moon’s compass direction, and the time it sets if you share your location.
- Why doesn’t this match my moon sign?
- Because they measure different things. A moon sign comes from the tropical zodiac, which divides the sky into twelve equal 30-degree slices anchored to the spring equinox rather than to the stars. Precession has drifted those slices about 24 degrees from the constellations they were named after since the names were fixed, so the sign usually runs a whole sign ahead of the constellation the moon is actually in. The panel reports both and labels which is which: the constellation is the astronomical answer, the tropical sign is the astrological one.
- How can it know my sky without asking for my location?
- Your device’s time zone stands in for a position on Earth, and sidereal time, the clock astronomers use to follow which stars have rotated into view, handles the rest. A time zone is a rough guess, so the page labels those directions approximate. Granting location access is optional; if you do, the reading is rounded to about seven miles, used only by the math running in your browser, and never sent to anyone.
- Will tonight’s sky look different tomorrow night?
- Both halves of the page move nightly. Stars rise about four minutes earlier each evening, so the three featured constellations slowly hand off to others in the pool of fifteen, and the moon steps one day further through its 29.53-day cycle, changing shape and name as it goes.
- Is this the real sky or a decorative picture?
- Every element drawn here is computed astronomy. Star positions and brightnesses come from published catalogs, the stick figures match the shapes on printed star charts, and southern-hemisphere visitors see each figure rotated 180 degrees, matching its orientation from their side of the equator. The math runs on your own device against the current time, so the figures on screen are calculated for the moment you opened the page.
Where these numbers come from
- Star positions and brightnesses are ICRS J2000 values from the d3-celestial project's public-domain-derived catalogs, checked against SIMBAD (CDS, University of Strasbourg); the stick figures follow d3-celestial and Stellarium's modern sky culture. Star labels use IAU Working Group on Star Names entries where they exist and Bayer or Flamsteed designations for most others; the faintest vertices go unlabeled.
- The moon phase uses the mean synodic month of 29.5306 days, referenced to the new moon of January 6, 2000, the standard mean-phase model, accurate to under a day.
- The moon's position comes from the periodic terms of Meeus'sAstronomical Algorithms, checked against NASA JPL's Horizons ephemeris at more than two thousand moments across 2025 to 2027, where the largest disagreement was a tenth of a degree. Constellation boundaries are the ones the IAU adopted from Delporte in 1930, in the machine-readable arrangement Nancy Roman published in 1987 and the CDS in Strasbourg distributes. Positions are precessed to the 1875 reference frame those boundaries are drawn in before they are looked up. Near a border the answer is uncertain: the moon is close enough to earth that where you stand shifts it by up to a degree.
- The tropical moon sign is the astrological reading, not an astronomical one: it is the moon's ecliptic longitude placed in twelve equal 30-degree divisions measured from the spring equinox.
- Sky placement uses Greenwich Mean Sidereal Time from the standard U.S. Naval Observatory expression. Without a shared location, your position is inferred coarsely from your clock's time zone, so directions are labeled approximate.
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