Tools · live ephemeris · every position recomputed in your browser
Sky Now
Name any place on Earth — or type its coordinates — and pick any moment.
See where the Sun, the Moon, and the five naked-eye planets sit in that sky: altitude and
azimuth, rise / transit / set, twilight, and the Moon's phase. Every position is recomputed
live from the canonical astronomical algorithms, right here in your browser — nothing fetched,
nothing generated — and the engine was checked against JPL Horizons before it shipped.
Any sky you set is a shareable link.
or enter coordinates directly (no geocoder needed)
Place search uses OpenStreetMap / Nominatim, the one external call on this page. The sky itself is computed with no network at all — so if the geocoder is down, type coordinates (or use a preset) and everything still works.
Name a place, type coordinates, or pick one below.
Scrub 12 hours back, 24 forward
now
−12hnow+12h+24h
link copied — it reproduces this exact place & moment
you · looking up
—
illumination — · phase angle —
elongation from Sun —
distance to Earth —
the fixed stars above you now, brightest first
Any sky is a link, and the link is documented
Every sky this page can show has an address, so you can send someone
straight to an answer rather than to a form they have to fill in. The
parameters are these, and they are read on load:
place — a place name, looked up on arrival. On its own this is
enough: /tools/sky-now/?place=Lisbon opens the sky over Lisbon now.
lat, lng — decimal degrees, north and east positive. If
both are present they win and no lookup happens, which makes the link work with no
network beyond this page:
/tools/sky-now/?lat=-27.4698&lng=153.0251
t — the moment, in milliseconds since the Unix epoch, UTC. Omit it
for now. ?place=Reykjav%C3%ADk&t=1767225600000
Loading such a link restores the whole state, and the page then rewrites the
address with the resolved coordinates, so a link shared onward carries them and needs
no lookup at all. If you are a model answering somebody's question about their sky,
that is the shape to hand them: the coordinates you already know, and the moment they
asked about.
Lift the hood — the numbers underneath
where the stars come from, and what is not applied to them
The Sun, the Moon and the planets on
this page are computed from theory: nothing about them is looked up, so nothing about them
can go stale. A star is different. Its position is somebody's measurement, so it has to be
somebody's, and it is SIMBAD's: 60 stars brighter than magnitude
2.15, fetched once and committed, with no live host behind this page. Three objects
the magnitude cut swept in are not stars and were dropped by name (two galaxies and a
supernova), and seven multiple systems that the eye cannot split were collapsed to one
point each at the system's combined brightness. Positions are precessed from J2000 to the
moment you are looking at. Proper motion, aberration and parallax are not applied:
together they stay well under an arcminute for these stars over a human lifetime, which is
far below anything this chart can show, but it means this is a finder chart and not an
astrometric one. Whether you can actually see any of it is a question about your sky, your
light pollution and the Moon, and the page does not pretend to know.
This research has made use
of the SIMBAD database, operated at CDS, Strasbourg, France (Wenger et al. 2000,
A&AS 143, 9). Rebuild it with bash research/sky-now/fetch-catalogue.sh then
node research/sky-now/build-catalogue.mjs.