The largest crewed satellite, orbiting about 400 km up and circling the Earth in about 90 minutes. It looks like a very bright, steady point crossing the sky in a few minutes. It is only visible around dawn or dusk, when it is sunlit while the observer is in darkness.
ToolsISS passes
Related terms
- Transit
A small object passing in front of a larger one without hiding it: Mercury across the Sun (next on 13 November 2032), one of Jupiter’s moons across the planet, or the ISS across the Sun or the Moon. For the Sun, a solar filter is essential.
- Twilight
The period when the sky darkens after sunset. It is civil until the Sun is 6° below the horizon (you can read outside), nautical until 12° (the horizon fades) and astronomical until 18°. Only then is the night truly dark for deep-sky objects.
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