Create a custom, naked-eye map of the whole sky for any place on Earth, at any time of day or night, on any date from 1600 to 2400.
When do the Sun and Moon rise and set? When does twilight end and begin? Which planets are up? Set our Online Almanac for your location!
Learn the phase of the Moon tonight, the day you were born, or on any historical date.
This interactive tool is designed to give you answers to your commonly asked questions about your telescope's performance when changing eyepieces and accessories.
Now you can calculate the dates and times (local and Universal Times) when the center of the Great Red Spot should cross Jupiter's central meridian, the imaginary line down the center of the planet's disk from pole to pole.
To compare what you see on Mars with a map, you need to know which side of the planet you're looking at. Our handy Mars Profiler tells you that and more, for any date and time.
Now you can calculate the dates and times (local and Universal Times) when the eclipsing variable star Algol should be at its dimmest (magnitude 3.4 instead of its usual 2.1).
The International Space Station often passes close to the Moon, Sun, and naked-eye planets. Use this tool to plan viewing these close encounters.
The International Space Station passes over virtually all of Earth's populated areas, and you can spot it easily with your eyes alone if you know where and when to look for it.
Numerous webmasters have asked us how to link to Sky & Telescope's Interactive Sky Chart so that the Java applet will open with a particular observing location already specified. This could be handy, for example, if the members of an astronomy club want to get a chart of the sky over their observatory via...
Are the constellations really upside down on the other side of the equator? What was that bright star in the west at dusk yesterday? Answer these and other cosmic questions with help from Sky & Telescope's Web site.
To make the most of our interactive observing tools, you need to indicate whether daylight saving time ("summer time") is in effect.