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Amateur astronomers use celestial navigation procedures to find specific satellites based on the ephemerides of each satellite and the viewer's specific location (using latitude and longitude data).
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When you have all the current information at hand you can reliably predict where in the sky to look at exactly what time, in order to see the satellite in question going by through your telescope's field of view.
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In this way viewers can repeatedly spot the ISS going by overhead several times every day. Sometimes it can be seen twice in the same hour.
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There is a video of some amateur astronomers capturing the ISS traversing the sun's disk just as the total solar eclipse of August 21st, 2017 was already in progress.