Comment by HPsquared
1 year ago
1. The satellite needs to be passing overhead at an angle where you can see it, and clear skies etc.
2. The sky needs to be dark enough to see it (so twilight or night)
3. The satellite needs to be illuminated by the sun.
4. The satellite needs to reflect enough light that you can see it.
Basically this happens just before sunrise, and just after sunset. So the ground and sky are dark (allowing you to see through the atmosphere), and the satellite - being at high altitude - is still illuminated.
As they pass overhead, you can often see them suddenly vanish as they pass into the Earth's shadow.
The International Space Station is a good one to find, as it's quite bright (very large).
There are various websites and apps; some phone apps use the GPS and magnetometer to show you what direction and time to look, and a search tool to look for visible objects at your location. It used to be really good with the old Iridium satellites, which gave a bright flash due to their large flat antennas.
I remember chasing one of the iridium flares and it was very bright, even during the day
> Basically this happens just before sunrise, and just after sunset.
I've seen plenty of satellites in the middle of the night, from very dark areas (wilderness). They look like stars, only they move more quickly. These observations go back a decade, at least.
I was mostly referring to the brightest things like the ISS, Starlink and (formerly) Iridium satellites, which are in low Earth orbit.
Higher orbits are visible for longer, due to the angles involved: because they're so high, such satellites can remain illuminated with the Sun further below the horizon. The Moon is the most extreme example: it's almost never in Earth's shadow.
> because they're so high, such satellites can remain illuminated with the Sun further below the horizon. The Moon is the most extreme example: it's almost never in Earth's shadow.
Very good point.
That doesn't seem right, why would they be bright?
That's a very good question. I'm sure of what I've seen, many times over years:
I can tell you that they look like stars - so much that I need a reference point, an actual star or planet, to verify they are moving and not a 'stationary' star (judging movement being otherwise very difficult at that distance). They move very steadily, horizon to horizon, or as far as I can track them. A wild guess, based on memory, is one might take 5 or 10 minutes to cross between my horizons (usually I'm not on a plain - trees, hills, mountains may elevate my 'horizons' and reduce the distance).
Natural celestial object? No way a star is moving that fast relative to other stars and Earth's horizons. Asteroid? That seems hard to believe, due to size and illumination. Comet? Are there lots of tiny ones? I never see tails. Maybe a meteorite entering the atmosphere that doesn't yet have a tail?
Other human-made objects? Airplanes would look bigger and have colored, blinking lights - I've seen plenty of airplanes at night. Maybe there are higher flying airplanes without the colored and blinking lights? Are they illuminated whitish, and so far away they'd look like stars?
I've seen them so many times, I'm confident that I could take anyone to a wilderness area on a clear night and find one within 15-20 minutes, probably less.
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I grew up in a rural area, on a moonless night, without a fire, as well as giving your vision some time to adjust to the darkness, you can see crazy amounts of stars along the Milky Way plane.
I would guess, reflected moonlight (moon over the horizon) would be enough to light up the dot well enough to see unaided.
They reflect sunlight for some period of the evening and morning, before the sun is shining where you are and illluminating the sky too much.
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In short: after sunset.