The International Space Station makes a spectacular site moving across the night sky. It usually takes about a minute to move across the sky. This sight is best appreciated with just your eyes. NASA makes it easy to know just when to look:
Transits of the ISS across the disk of the Sun or Moon last only a second or less so use a telescope and don't blink. They are great photography opportunities with a telescope or very long lens (use appropriate equipment and great caution observing or photographing the Sun). ISS transits are only observable along very narrow (a couple of miles wide) paths along the ground.
ISS Transit Finder is a great tool for finding when and where to observe. It can make calculations up to seven weeks in advance. The ISS makes small orbital adjustments. It is best to recheck the ground track, a few days and a few hours before, to get the most accurate estimate. An example of the information you can get from ISS Transit Finder:
Another good on-line tool for planning observations of the ISS is CalSKY.
Content created: 2016-06-04
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