<p>My first thought would be that the apparent path of a satellite across the sky can appear to turn even when it is straight.  Your brain doesn't easily understand straight lines in all cases.  (Look up lunar terminator illusion)</p>

<p>I've several times seen Mir/ISS passes that seem to arrive from one direction, appear to turn, then leave in some unrelated direction.  It's always really moving in a straight line though.  </p>

<p>Web sites can show you what path the satellite will make across the starfield, but it can't simulate the illusion you might have on seeing it from the ground.</p>

<p>The ground track alone can't tell you the visibility from the ground because it also depends on altitude.  A low-earth-orbit satellite might be visible from a circular patch about 3000km in diameter.  Higher altitude objects would be fainter, but visible across a wider area.    </p>

CC BY-SA 3.0
2016-10-13T19:57:06.820Z
2016-10-13T19:57:06.820Z
BowlOfRed
<p>It is not that satellite. As it passes over Finland, it has an altitude of 27000km and a magnitude of about 12. You won't see it. All Molniya orbits are similar.</p>

<p>The website <a href="http://www.satflare.com/track.asp?q=15214#TOP" rel="nofollow">Satflare</a> to shows the region in which satellites are visible (it uses a blue ring around the satellite) Your satellite was so high that it was visible from nearly the whole hemisphere.</p>

<p>I won't try to identify your object, except to say that an object as described is not in orbit.</p>

CC BY-SA 3.0
2016-08-13T11:39:55.350Z
It was after my post that I found a different website that displayed the ground track over a flat map and next to it, the 3D representation of the orbit around the spherical planet. You're definitely right then, it couldn't have been that particular satellite and I can see why. But what link are you talking about? I came across several different satellite tracking websites and my post doesn't mention any by name or have links. I Googled my observation and noticed that many other people report having seen a similar thing, but there's no satisfactory explanation yet.
user158589
CC BY-SA 3.0
2016-08-14T10:35:19.673Z
Sorry. I've now linked to the website that I used.
James K
CC BY-SA 3.0
2016-08-12T23:14:35.693Z
2016-08-14T10:33:56.547Z
2016-08-14T10:33:56.547Z
James K
<p>On a casual star walk, (for comparison of identifying different objects) I witnessed some meteors, quite a few satellites gliding on their smooth and straight trajectories, and some airplanes with their much brighter (sometimes blinking) lights, lower altitude and the characteristic sense of moving towards and away from me. Suddenly one of the satellites seemed as if its motion had been a bit jittery, and its path started to curve inwards in an asymmetrical, gentle and large C-shape. The airplanes made noise, this one did not. Visually perfectly identical with all of the normal satellites. I had never seen anything like that before so I wondered if it could've been some debris colliding into things, but probably not. The best explanation I have for now is that it apparently might have been a satellite on a Tundra or Molniya orbit, as their ground tracks aren't the usual straight or sine wave shaped trajectories that we're used to. Most satellite tracking websites either didn't seem to have tracking options for those special types at all, or you could only see their locations for now, not a custom time. </p>

<p>I'm in the capital city area of Finland, and when I saw the object, the time was 23:10 on the UTC+3 time zone, 12th of August 2016. Of what I found, the only strange looking ground track that comes even close would be Molniya 1-62, drawing a loop above Finland. What I can't find is a website that would allow me to rewind time to check where the satellite was at 23:10. But whether or not I should keep searching for that info.</p>

<p><strong>I first have this question: If I look at the satellite tracks going across a map, how do I determine how far a satellite would be visible when viewed from the ground?</strong> If I looked at similar tracks for airplanes, it's much easier to understand that the ground area from which an airplane can be spotted doesn't span vast distances, but how this compares to a satellite is difficult to imagine as we don't perceive them in a three dimensional space, but spots gliding across the flat surface of a dome. </p>

<satellite><eccentric-orbit>
Actual observable horizon for satellites on an orbit line map?
user158589
# Actual observable horizon for satellites on an orbit line map?

(Asked by: username_0 on 2016-08-12)

On a casual star walk, (for comparison of identifying different objects) I witnessed some meteors, quite a few satellites gliding on their smooth and straight trajectories, and some airplanes with their much brighter (sometimes blinking) lights, lower altitude and the characteristic sense of moving towards and away from me. Suddenly one of the satellites seemed as if its motion had been a bit jittery, and its path started to curve inwards in an asymmetrical, gentle and large C-shape. The airplanes made noise, this one did not. Visually perfectly identical with all of the normal satellites. I had never seen anything like that before so I wondered if it could've been some debris colliding into things, but probably not. The best explanation I have for now is that it apparently might have been a satellite on a Tundra or Molniya orbit, as their ground tracks aren't the usual straight or sine wave shaped trajectories that we're used to. Most satellite tracking websites either didn't seem to have tracking options for those special types at all, or you could only see their locations for now, not a custom time.

I'm in the capital city area of Finland, and when I saw the object, the time was 23:10 on the UTC+3 time zone, 12th of August 2016. Of what I found, the only strange looking ground track that comes even close would be Molniya 1-62, drawing a loop above Finland. What I can't find is a website that would allow me to rewind time to check where the satellite was at 23:10. But whether or not I should keep searching for that info.

**I first have this question: If I look at the satellite tracks going across a map, how do I determine how far a satellite would be visible when viewed from the ground?** If I looked at similar tracks for airplanes, it's much easier to understand that the ground area from which an airplane can be spotted doesn't span vast distances, but how this compares to a satellite is difficult to imagine as we don't perceive them in a three dimensional space, but spots gliding across the flat surface of a dome.

**Tags:** satellite, eccentric-orbit

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## 2 answers

### Answer by username_1 on 2016-10-13. Score: 2

My first thought would be that the apparent path of a satellite across the sky can appear to turn even when it is straight. Your brain doesn't easily understand straight lines in all cases. (Look up lunar terminator illusion)

I've several times seen Mir/ISS passes that seem to arrive from one direction, appear to turn, then leave in some unrelated direction. It's always really moving in a straight line though.

Web sites can show you what path the satellite will make across the starfield, but it can't simulate the illusion you might have on seeing it from the ground.

The ground track alone can't tell you the visibility from the ground because it also depends on altitude. A low-earth-orbit satellite might be visible from a circular patch about 3000km in diameter. Higher altitude objects would be fainter, but visible across a wider area.


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### Answer by username_2 on 2016-08-12. Score: 2

It is not that satellite. As it passes over Finland, it has an altitude of 27000km and a magnitude of about 12. You won't see it. All Molniya orbits are similar.

The website [Satflare](http://www.satflare.com/track.asp?q=15214#TOP) to shows the region in which satellites are visible (it uses a blue ring around the satellite) Your satellite was so high that it was visible from nearly the whole hemisphere.

I won't try to identify your object, except to say that an object as described is not in orbit.

> **Comments:**
> **username_0**: It was after my post that I found a different website that displayed the ground track over a flat map and next to it, the 3D representation of the orbit around the spherical planet. You're definitely right then, it couldn't have been that particular satellite and I can see why. But what link are you talking about? I came across several different satellite tracking websites and my post doesn't mention any by name or have links. I Googled my observation and noticed that many other people report having seen a similar thing, but there's no satisfactory explanation yet.  
> **username_2**: Sorry. I've now linked to the website that I used.  

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