The altitude and number of passes increases nightly and then tapers off, to be followed by a period of daytime-only passes until it reappears at dawn. You might first spot it in the evening sky, very low in the south, as it makes a single pass a night. ISS 'viewing seasons' are cyclic, with each lasting several weeks. It's visible at least 10° above the horizon between 63°N and 63°S as well, guaranteeing that nearly every person on Earth has a chance to see it. Thanks to the steep 51.6° inclination of its orbit, the station passes overhead for anyone living between latitudes 51.6°N and 51.6°S. Few naked-eye sky sights elicit more wows at public star parties than the Venus-bright 'star' speeding through the constellations. Now in its 21st year in orbit, the ISS is the brightest, most recognizable satellite in the sky. Inside that bright light, a crew of several astronauts looks earthward with the same sense of wonder. I've seen the International Space Station (ISS) pass over my house a hundred times yet never tire of the sight. At times reaching magnitude –3.9, the ISS rivals Venus in brightness. The International Space Station (ISS) slices across Perseus and Taurus in a time exposure made on August 11, 2011. The annual International Space Station marathon viewing season begins later this week, when skywatchers in the Northern Hemisphere can watch up to five ISS passes in one night.
