Home › Astronomy
A star chart centered on your sky — and, under it, the cast list. The twenty stars below are the ones with stories: eclipsing demons, golden doubles, unstable giants. On the map they wear gold rings; in the list, only the ones actually up at your chosen time appear, highest first.
North at the top, east on the left (as it is when you look up), the center is overhead. Gold-ringed stars are the watch list below.
The chart is computed for your place and the exact minute you choose, from the same verified machinery as the Sky Simulator — Yale Bright Star Catalog positions carried to altitude and azimuth by the local sidereal time, drawn stereographically with the zenith at the center.
The watch list is a human selection, not a computation: twenty stars chosen because something is happening at each of them — an eclipse, an orbit, an unstable atmosphere, a companion burnt to a cinder. Their positions, altitudes and directions are live; their stories are the accumulated observations of centuries. When a star falls below the useful sky it leaves the list, which is why the cast of a winter evening (Orion's Rigel and Betelgeuse, the Twins) differs completely from a summer one (Vega, Deneb, Albireo).
Because a star map is held up to the sky, not laid on a table. Look up with north behind you and east is at your left hand. Every printed star atlas uses the same convention.
The list only shows watch stars that are actually above your horizon at the chosen time and at least 8 degrees up. Drag the time slider, or change the date — the cast rotates with the seasons.
Albireo and Almach yield to good binoculars held steady, and to any small telescope. Mizar’s companion Alcor needs no equipment at all — just decent eyes and a dark sky.
Possibly — it fades every 2 days, 20 hours and 49 minutes, like clockwork, and the dimming lasts about ten hours. If Algol looks fainter than the stars around it tonight, you are watching one star pass in front of another, 93 light-years away.