Sky Watch: Tracking satellite passes

One of my favorite springtime activities is to watch satellites pass across the early evening sky.

I'm sure you've seen them too; it's hard to miss them with so many orbiting our planet these days.

So how does one know when and where to look? With the Internet and smartphones, it's really quite easy. While there are many apps available that provide times and locations of bright satellites, my favorite website for predicting satellite passes is heavens-above.com.

Once there, register. It's free and it'll make your future visits more productive. Not only will you learn which satellites are passing over your neighborhood, but you'll also find times of sunset, sunrise and twilight, phases of the moon, and much more.

To use these features, you must tell the program where you're located -- either by selecting your town from its massive database, or by entering your latitude and longitude manually.

Once located, you can learn the details of upcoming satellite passes. My favorite feature comes from clicking the time of a satellite's maximum altitude: a sky map appears, showing a satellite's path across the constellations.

Now let's say that you learn that the International Space Station or the Hubble Space Telescope will be making a great pass tonight and you'd like to see it.

Make sure your watch is set to the correct time. Go outdoors and look along the satellite's projected path for a "star" that appears to be drifting slowly in the correct direction. Don't be fooled by one with blinking red and green lights; this is not a satellite! And always begin your watching session a few minutes early.

In the evening sky, a satellite will appear faint at first and brighten as the sun's light illuminates it. Sometimes it will catch a brief glint of sunlight and brighten rapidly. And don't be surprised if the satellite eventually fades away while still in the sky; it's just entered the shadow of Earth. Photographing an Earth-orbiting satellite is easy too. With your camera on a sturdy tripod, aim it toward one of the constellations along the satellite's path. With everything in "manual" mode, focus on infinity, set your aperture as wide open as possible, make sure your ISO is around 400 or 800 and the exposure set for "bulb" (or whatever setting allows you to take long time exposures). Be sure to try some test exposures just before the satellite appears so you can make adjustments to your settings.