International Space Station

The International Space Station (ISS) regularly passes through our skies. It appears like a very bright star moving from west to east, at an angular velocity similar to a plane, and taking a few minutes to cross the sky. During morning passes, especially the very early morning ones, the satellite may be in the Earth’s shadow, and therefore invisible, for the first part of a pass. Similarly, the satellite may enter the Earth’s shadow during the late evening passes, and disappear from view. Note that many other, fainter, satellites are also visible. The ISS is by far the brightest, being as large as a football pitch.

Heavens-Above is an excellent website which provides up-to-date predictions of the ISS and many other satellites for your exact location. For most visual purposes you can use Guernsey on Heavens-Above as an accurate enough location. Then click on “ISS” for Space Station predictions. The table then shows:

• The local time, altitude (in degrees above the horizon) and compass direction to look when it first becomes visible.
• The time, altitude and direction when it reaches maximum altitude.
• And the time, altitude and direction when it disappears.

In the evening the “end” time may be when it disappears into the Earth’s shadow; and in the morning the “start” time may be when it emerges from the Earth’s shadow.

Transits

If you're interested in attempting to capture a transit of the ISS across the Sun* or the Moon, your exact and accurate coordinates are more important. A transit will show the silhouette of the space station as it passes across the bright object behind. These transits are very quick, about 1 - 1.5 seconds if you're in the correct location, so preparation and planning is important. For this purpose, you may find this Transit Finder website of interest.