Most people have no idea that on almost any clear night, if you know where and when to look, you can watch a space station sail over your house. No telescope, no binoculars, no equipment at all except your eyes and a watch. I've been hooked since a friend dragged me out into a parking lot in 1997 and pointed at a moving star and said "that's Mir." This page is my attempt to get you hooked too.

About me: I'm a physics grad student, which sounds fancier than it is (it mostly means I grade lab reports). I observe from the parking lot behind my apartment building, or on good nights from a friend's farm twenty minutes out of town where the sky is actually dark. I don't own a telescope. You don't need one for this.

Mir. The Russian space station, in orbit since 1986, about 240 miles up. Mir is the easy one: on a good high pass it's as bright as the brightest stars in the sky and moves steadily from one side of the sky to the other in about five minutes. It has been occupied almost continuously for years, but the last crew came home on August 28 and Mir is flying empty right now. It still shows up fine. Go see it while it's there; there is a lot of talk about how much longer it will be kept up.

The International Space Station. So far the new station is just two pieces: the Russian-built Zarya module, launched on November 20, 1998, and the American Unity node, carried up by the Shuttle Endeavour in December 1998 and bolted on. It's noticeably fainter than Mir, about like the stars of the Big Dipper, because there's not much of it yet. The Russian service module that will let crews live aboard is now scheduled for next year. It'll get bigger and brighter every year for a while, and I think it's kind of wonderful to be able to say "I saw it when it was only two modules."

Iridium flares. This is the one that makes people gasp. The Iridium satellite-phone constellation (66 satellites plus spares, about 485 miles up) has three flat, door-sized antennas on each satellite that are polished like mirrors. When the geometry is just right, one of them reflects the Sun straight down at you and for five to twenty seconds a point of light brightens up out of nowhere, sometimes to brighter than Venus, and then fades away. It's predictable to the second and to within a few miles on the ground. The company that runs the phones is in bankruptcy this summer, which has been in the news, but the satellites are still up there flaring away.

The Space Shuttle. When one is in orbit it's a nice bright pass on its own, and when it's docked to or just separated from a station you can see two dots flying in formation, which is the coolest thing I've seen from a parking lot. There's no Shuttle flying this month, so watch the news and check back.

Everything else. Once you start looking you'll notice faint "stars" drifting through the constellations all night: old rocket bodies, weather satellites, spy satellites nobody will confirm. There are hundreds of them bright enough to see. Some tumble and flash slowly as they go.

Nothing on this page works without a prediction, so here's the general idea.

A satellite in low orbit goes around the Earth once every 90 minutes or so at about 17,500 mph. Its orbit is described by a short set of numbers called orbital elements: how tilted the orbit is, how high, where the satellite was at a certain moment, and so on. Radar tracking stations measure these regularly and the element sets get passed around among hobbyists. Given the elements and your latitude and longitude, a computer program can grind out where the satellite will be in the sky, from your spot, minute by minute, for the next several days. I get fresh elements from the computer at school and run a prediction program on my Pentium at home. A printout of the week's passes lives on my refrigerator.

Two more things have to be true for you to see it. First, the satellite has to be in sunlight while you are in darkness. That's why passes happen in the hour or two after sunset and before sunrise: the Sun has set for you but not yet for something 240 miles up. In the middle of the night the satellite is in Earth's shadow and invisible. Second, it has to pass reasonably high in your sky; a pass that only gets 10 degrees above the horizon is lost in trees and haze.

Elements go stale. Air drag slowly lowers a station's orbit and it gets boosted back up now and then, so a prediction made from two-week-old numbers can be off by a minute or more. Fresh elements, good predictions.

• Know your compass directions. Predictions say things like "rises in the southwest, peaks 62 degrees high in the northwest." Figure out which way is which from your spot in the daytime. The Sun sets roughly in the west; that's a start.
• Know what a degree looks like. Your fist at arm's length is about 10 degrees. Straight overhead is 90. "Peaks 45 degrees high" means halfway up the sky.
• Be outside early. Get out five minutes before the pass with your watch set to the right time. Satellites do not wait.
• Look an hour after sunset. The best passes are about one to two hours after sunset or before sunrise: sky dark enough, satellite still lit. Passes right at dusk are hard because the sky is still bright.
• Dark helps, but a city is okay. Mir and Iridium flares are bright enough to see from a lit parking lot. The station and the fainter stuff want a darker spot and a few minutes for your eyes to adjust.
• It's not blinking. A steady moving light is a satellite. A blinking one, red and green, is an airplane. If it makes noise, it's an airplane.
• Don't panic when it vanishes. A satellite will often fade out in mid-sky. That's it going into Earth's shadow, not disappearing. It's still up there.
• Bring a friend. Half the fun is the "THERE it is!"

Times are local. Directions are where it came up and where it went down. "Max" is the highest point of the pass.

Q. Do I need a telescope?
A. No. In fact a telescope is nearly useless for this; the satellite crosses the field of view in a fraction of a second. Eyes only. Binoculars can help you find the fainter ones and are fun for following the station.

Q. Does it blink?
A. No. Airplanes blink. Satellites shine with steady reflected sunlight. (A few old tumbling rocket bodies pulse slowly, but that's a slow fade-in-fade-out, not a blink.)

Q. Why did it just disappear in the middle of the sky?
A. It flew into the Earth's shadow. Perfectly normal. The prediction will usually tell you where that will happen.

Q. How fast does it move?
A. About as fast as a high airplane looks, horizon to horizon in three to six minutes. It doesn't zip; it cruises.

Q. Can I see the satellites that carry TV signals?
A. Not with your eyes. Those are in geosynchronous orbit 22,000 miles out, which is why your dish never has to move. They're far too faint. Everything on this page is in low orbit, a few hundred miles up.

Q. Can I see it from the city?
A. Mir and Iridium flares, yes, easily. The station, probably, if you know where to look. The faint stuff, no.

Q. What time is best?
A. Roughly an hour to two hours after sunset, or before sunrise. Never the middle of the night.

Q. Was that a UFO?
A. If it moved steadily in a straight line, didn't blink, and faded out, it was a satellite. If you're not convinced, my fellow skywatcher Kevin keeps a whole page of UFO sighting reports and would love to hear from you. We disagree about a few things and get along fine.

Q. Can you send me predictions for my town?
A. If you e-mail me your city, I'll try to run a week of passes for you when I have time between lab reports. No promises on turnaround, and please tell me your time zone.

• Steve's Model Rocketry Page -- Steve and his son launch the kind of rockets you can see the whole flight of.
• Kevin's UFO Sighting Reports -- see the FAQ above.
• Weather Watching with Walter -- because "clouded out" is half of my log.
• Mr. Delgado's 7th Grade Science -- teachers, satellite spotting makes a great class project. Everybody can do it from home.
• Back to the CapeCanaveral neighborhood