Why can we see satellites?

[Jinx]

@Xema

To be additionally pedantic, I’ll note that if geosynchronous satellites were visible, they would definitely move (albeit reasonably slowly) against the starry background. After all, the Moon - quite a bit further than any artificial satellite - does so.

Uh…have you noticed the moon is NOT in a geosynchronous orbit?

[scr4]

@Jinx

Uh…have you noticed the moon is NOT in a geosynchronous orbit?

Which is why he said it’s further away than artificial satellites. The point is, even at that distance, the moon’s movement relative to the stars is noticeable.

[Mangetout]

@scr4

Well, the movement is how you know it’s a satellite. But many satellites are bright enough that you’d see them even if they weren’t moving. They’d just look like ordinary stars.

The ones I’ve seen would look like very dim, insignificant stars - I suppose, yes, they’d be visible if they weren’t moving and were pointed out, but it’s still true that the human visual system is more sensitive to moving things than static ones. It’s conceivably possible to have a speck that is against a blank background that we would have great difficulty finding/perceiving, until it moved.

[Mangetout]

@Q.E.D.

I wanted to add: Geostationary satellites don’t move with respect to the stars, but geosynchronous ones appear to bob up and down with a displacement which depends on the orbit’s tilt with respect to the equator.

“Geostationary satellites don’t move with respect to the stars”

Bwuh?

Do you just mean the stars appear to move with respect to the stationary satellite - not the other way around - or do you mean something else?

[Q.E.D]

@Mangetout

Do you just mean the stars appear to move with respect to the stationary satellite - not the other way around - or do you mean something else?

No, I mean I’m an idiot. Ignore all that. Or substitute “ground” for “stars” if you prefer.

[KneadToKnow]

@Q.E.D.

Or substitute “ground” for “stars” if you prefer.

I like that solution better.

'Cause that means I can fly anywhere I can walk!

[Mangetout]

Never mind - we all make mistakes. Except me, of cpurse.

[Capt.Ridley_s_Shooting_Party]

@Jinx

This reply is for Phlosphr, ShagNasty, and anyone else who has seen the same thing: What time of day/night are you seeing these? I know I’ve seen these things as late as 1-2am, but the SDopers told me satellites can only be seen shortly before/after sunrise/set, respectively. The SD argues the satellite would be on the ‘dark side’ of the earth by then; yet, what else could it be??? Operation Fail-Safe fighter jets, perhaps?

Your experience is the same as mine. The only time I’ve seen satellites in the night sky was in Canada, in an island in the middle of a lake (the UK has too much light pollution). It was pitch black, in the middle of summer, definitely some time after dusk, and we could see them for a couple of hours after we first observed them, at least.

[Ponderoid]

More than once, I’ve had satellites go whizzing through my field of view in my telescope while I was out observing. Never planned, always serendipitous. It was fun the one time I had the presence of mind to grab the scope and manually track it along with the satellite for a few minutes. It didn’t resolve to anything more than a point, even in the 12-inch scope I was using. I was unable to make that particular one out with my naked eyes when I looked up to try; the light pollution was too much to see it without the scope.

I’ve had airplanes wander through too, and those usually do resolve quite well to see some details, but usually at night all you get are the positions of the different marker lights.

*** Ponder

[Freddy_the_Pig]

@Jinx

I know I’ve seen these things as late as 1-2am, but the SDopers told me satellites can only be seen shortly before/after sunrise/set, respectively.

Not necessarily. The trick is that the Sun has to shine on the satellite but not on the upper atmosphere–a combination generally realized when the Sun is between, maybe . . . 12 and 25 degrees below the horizon. (The exact numbers depend on the height of the satellite.) From the mid-latitudes near the summer solstice, the Sun will stay in that range most of the night. Closer to the tropics, and closer to the equinox, you’re restricted to a more narrow band after sunset and before sunrise.