Triangulating the Position and Height of the International Space Station (ISS)

Mick West

Administrator
Staff member
@DJC, I think it would be very useful if you actually observe the ISS flying overhead, so you know what we are talking about.

Tonight, from 10:13PM to 10:19PM there will be an excellent ISS transit over Hamilton, Ontario, Canada (which you said was your location).

It will start out as a dim moving light in the southwest, and gradually brighten and seem to speed up as it gets closer, and higher in the sky. at around 10:16 it will be nearly overhead, at 80° above the horizon. Then it will seem to descend as it moves towards the horizon, getting dimmer, and setting in the north east.

It's a great opportunity to get some perspective on this discussion, and you only get viewing opportunities like this every few weeks, so I highly encourage you to watch it tonight.

https://spotthestation.nasa.gov/sightings/view.cfm?country=Canada&region=Ontario&city=Hamilton#.V5j3NJMrLmE
20160727-111147-5qw89.jpg
 

DJC

Member
@DJC, I think it would be very useful if you actually observe the ISS flying overhead, so you know what we are talking about.

Tonight, from 10:13PM to 10:19PM there will be an excellent ISS transit over Hamilton, Ontario, Canada (which you said was your location).

It will start out as a dim moving light in the southwest, and gradually brighten and seem to speed up as it gets closer, and higher in the sky. at around 10:16 it will be nearly overhead, at 80° above the horizon. Then it will seem to descend as it moves towards the horizon, getting dimmer, and setting in the north east.

It's a great opportunity to get some perspective on this discussion, and you only get viewing opportunities like this every few weeks, so I highly encourage you to watch it tonight.

https://spotthestation.nasa.gov/sightings/view.cfm?country=Canada&region=Ontario&city=Hamilton#.V5j3NJMrLmE
View attachment 20088
I'm going to take pics ........ill post them tnite
 

Mick West

Administrator
Staff member
I'm going to take pics ........ill post them tnite
Make sure before that you can take photos of stars. Take a few test shots of stars first.

It might be better to take video. Unless you've got a super-zoom lens then you are just going to see a bright dot, and seeing the path of the station is more interesting than a few photos of a dot.
 

deirdre

Moderator
Staff member
Make sure before that you can take photos of stars. Take a few test shots of stars first.

It might be better to take video. Unless you've got a super-zoom lens then you are just going to see a bright dot, and seeing the path of the station is more interesting than a few photos of a dot.
i was going to say that. i can see it here at the same time as DJC, but i only have a lumix DMC-sz3 camera. if i video the sky will it show up? do i try to find it in the zoom or just leave it regular... also if you think its possible for me to capture it at same time... then iill give you my exact location (no lights) and maybe you guys can tell me exactly where in the sky i should be looking. and i dont mean 30degrees west, i mean can you'd have to tell me in a way i can understand, otherwise by the time i figure out where im supposed to be looking i'll probably miss it.
 

Mick West

Administrator
Staff member
i was going to say that. i can see it here at the same time as DJC, but i only have a lumix DMC-sz3 camera. if i video the sky will it show up? do i try to find it in the zoom or just leave it regular... also if you think its possible for me to capture it at same time... then iill give you my exact location (no lights) and maybe you guys can tell me exactly where in the sky i should be looking. and i dont mean 30degrees west, i mean can you'd have to tell me in a way i can understand, otherwise by the time i figure out where im supposed to be looking i'll probably miss it.
It will probably show up without zoom if it gets high enough, however it looks like it's only going to get to 42° above the horizon from where you are. That won't be be brightest. Still might work though. You should have a minute or two to experiment.

As or where to look, do you have a compass? Like the compass on the iPhone? Turn it to point north, they you can see the S, SW, W directions. WSW is West of South West, and SSW is South of SouthWest. So if the ISS going to appear above WSW, then look in that direction.
20160727-123139-wqadb.jpg

You might find it easier to look at your house in Google Maps, and then see where WSW is relative to a wall or corner of your house, like (random location example)
20160727-124056-j0di3.jpg
 

Mick West

Administrator
Staff member
With two places that have very similarly timed views you can do a ballpark calculation of the altitude of the object given the peak angles and the distance between the view locations.

Say we take @DJC roughly in Hamilton, ON, and @deirdre roughly in Danbury, CT, we have:

Hamilton:
20160727-124813-xyvl3.jpg

Danbury:
20160727-124734-3kvls.jpg

Now they both start at about the same time and last six minutes. So when it's at the highest point it's going to be roughly between the two locations (not quite, as the start times differ, but close enough for ballparking)

So we've got two points, roughly 370 miles apart, and another point (the ISS) that's visible between them, 81° up from one, and 42° from the other. Hello high school trig:
20160727-130750-sji7p.jpg
Now this is a very rough ballpark figure, but it puts the ISS at 287 miles above the ground, and the real figure is about 250. It's off because of (the same reasons as) the 1 minute difference, and (funnily enough) not accounting for the curvature of the Earth. However, it's still showing that two people are observing this thing pretty much where it is supposed to be. So there's SOMETHING there that multiple people can see as predicted, and that only works out if it's orbiting a globe.
 

Chew

Senior Member
I'm going to take pics ........ill post them tnite
Stellarium shows the ISS will be closest to the star Vega at 10:16:33 your time as seen from your location. It will pass 2.5° from it (about the width of one finger held at arm's length).

stellarium-021.png
 

Mick West

Administrator
Staff member
And another interesting thing, if we take a photo at the exact same time of the ISS from those two locations, then the stars behind the ISS will be very different. Here's what it's going to look like from Danbury, CT at 22:16:55 Eastern Daylight time (UTC-4)
20160727-140656-z8cem.jpg

Notice that the ISS will be passing through the "Big Dipper" constellation at that time. Right by the third star (Alioth).

Now from Hamilton, Ontario, the picture is radically different.
20160727-141650-pl641.jpg

Notice I had to zoom back a lot to get the ISS, the Big Dipper, and the horizon all in the same image. See how the ISS is no longer anywhere near the Big Dipper (it's up near Vega, as Chew noted), in fact this photo is a little misleading as the ISS passes a bit to the south, and here I'm looking north, essentially bending over backwards a bit to be able to see it.

This is an interesting practical demonstration of how much things shift when viewed from a few hundred miles apart, and how the stars don't shift at all, because they are trillions of miles away.
 

Inti

Active Member
And another interesting thing, if we take a photo at the exact same time of the ISS from those two locations, then the stars behind the ISS will be very different. Here's what it's going to look like from Danbury, CT at 22:16:55 Eastern Daylight time (UTC-4)
View attachment 20105

Notice that the ISS will be passing through the "Big Dipper" constellation at that time. Right by the third star (Alioth).

Now from Hamilton, Ontario, the picture is radically different.
View attachment 20106

Notice I had to zoom back a lot to get the ISS, the Big Dipper, and the horizon all in the same image. See how the ISS is no longer anywhere near the Big Dipper (it's up near Vega, as Chew noted), in fact this photo is a little misleading as the ISS passes a bit to the south, and here I'm looking north, essentially bending over backwards a bit to be able to see it.

This is an interesting practical demonstration of how much things shift when viewed from a few hundred miles apart, and how the stars don't shift at all, because they are trillions of miles away.
I feel quite excited to hear how this turns out. Hope you both have good weather,
 

Mick West

Administrator
Staff member
So I calculated the point at which the ISS will be exactly in line with Hamilton and Danbury it's slightly earlier than the Big Dipper intersect, at 10:16:29
20160727-160203-c82i6.jpg

From Danbury this looks like (note the position of the big dipper).
20160727-160544-rgncw.jpg

Zooming out you can see the curve of the earth between Hamilton on the left and Danbury on the right, significant when it comes to obscuring things, but not that relevant for something 250 miles high.
20160727-160900-nokb7.jpg
 
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DJC

Member
We just got in at around 10 15 we saw what looked like with the naked eye a larger the normal light travelling towards the north east from hamilton airport area towards the lake ....without proper zoom you couldn't make out any features.....i had a change of plans so i couldn't get properly prepared but we have video I'm going to screen shot it and upload the pics
 

deirdre

Moderator
Staff member
i saw it and it was super cool. my video captured nothing but fairy lights earlier. it might have gotten the iss if i could have found it in my view camera fast enough, but where i parked i only had a window about 3x the dipper and a cop was trying to help me (yes with his car lights on) with my camera work ;/ :) but it really did hit the dipper.. which was clear as a bell in reality..at exactly the time Mick said it would and i got a pic of it but youd have to take my word for it that it was the iss. this shot is exactly as it hit the dipper handle...honest.
dipperiss.JPG

and passing the dipper... it was me who moved, not the iss.
iss2.JPG

and an airplane i got a few minutes earlier. i dont know why the stars dont show at all they seemed bright.
airplane2.JPG
 

Attachments

DJC

Member
i saw it and it was super cool. my video captured nothing but fairy lights earlier. it might have gotten the iss if i could have found it in my view camera fast enough, but where i parked i only had a window about 3x the dipper and a cop was trying to help me (yes with his car lights on) with my camera work ;/ :) but it really did hit the dipper.. which was clear as a bell in reality..at exactly the time Mick said it would and i got a pic of it but youd have to take my word for it that it was the iss. this shot is exactly as it hit the dipper handle...honest.
View attachment 20114

and passing the dipper... it was me who moved, not the iss.
View attachment 20115

and an airplane i got a few minutes earlier. i dont know why the stars dont show at all they seemed bright.
View attachment 20118
We were facing the dipper but it came more from the south it didn't pass the dipper not for us anyway ......
 

DJC

Member
Question .....how was the ISS so bright and how can we tell it was not just flying at a higher altitude straight and not in orbit ..and whatever we saw last year was def not this but it got a little over cast around 8 pm as well
 

deirdre

Moderator
Staff member
We were facing the dipper but it came more from the south it didn't pass the dipper not for us anyway ......
it was alot bigger and brighter than i was expecting it to be. clear skies bright stars but it was brighter than the stars. i couldnt make out with my eye any detail though, just a white blob.
 

deirdre

Moderator
Staff member
Question .....how was the ISS so bright and how can we tell it was not just flying at a higher altitude straight and not in orbit ..and whatever we saw last year was def not this but it got a little over cast around 8 pm as well
i think youd need 2 people with better cameras (well yours may be good) to take pics of it at the same time, and youd see that no plane can fly that high. ex: if my stars showed up youd see it was at the big dipper for me. You should pick a friend or family member you trust a few hundred miles away and plan a simultaneous shoot.

Planes can only fly up to a certain altitude really (plus you almost always see red or green lights on them) so i dont think youd see it at the same time hundreds of miles away.
 

Mick West

Administrator
Staff member
Question .....how was the ISS so bright and how can we tell it was not just flying at a higher altitude straight and not in orbit
It's bright because it's lit by the sun. The web site gives times when you can see it. It's actually above you a lot more, but it's either in daytime, or it's night and the ISS is in the Earth's shadow.

It's not really that bright. It just looks incredibly bright because it's dark. Compare a flashlight at night to a flashlight in the daytime in direct sun.

We can tell it's in orbit because of the path it takes. It goes up and then down to the horizon. If the earth was flat then people 200 miles from you would seeing it rise up from a hole in the ground. There's simply no way to make it work with multiple observers unless the Earth is a globe.
 

DJC

Member
It's bright because it's lit by the sun. The web site gives times when you can see it. It's actually above you a lot more, but it's either in daytime, or it's night and the ISS is in the Earth's shadow.

It's not really that bright. It just looks incredibly bright because it's dark. Compare a flashlight at night to a flashlight in the daytime in direct sun.

We can tell it's in orbit because of the path it takes. It goes up and then down to the horizon. If the earth was flat then people 200 miles from you would seeing it rise up from a hole in the ground. There's simply no way to make it work with multiple observers unless the Earth is a globe.
Sorry its a bit late maybe I'm just not getting it ....Where is the sun right now to light up the ISS ....the suns rising in Europe right now
 

CeruleanBlu

Active Member
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DJC

Member

Mick West

Administrator
Staff member
I just saw this amazing huge fireball flying overhead here (Shingle Springs, California). I gaped at it for a second got out my phone and started recording. Result - black video. I think I actually started recording when I put it back in my pocket. I'm super miffed I missed it. It was huge and lasted around 15-20 seconds.

Point being, it's hard to take photos of the night sky without preparation.
 

deirdre

Moderator
Staff member
That doesn't look to real .......and it didn't arc in our line of sight ...it flew across the sky ....
i didnt notice an arc either but my view window of the sky was only about this big
bd.JPG


it looked exactly like that too. except im not sure it went "up" as much at the end there.. but its hard to tell cause my camera was moving so much.. i didnt see it until about hte red x because i was chatting.
 

DJC

Member
i didnt notice an arc either but my view window of the sky was only about this big
View attachment 20120


it looked exactly like that too. except im not sure it went "up" as much at the end there.. but its hard to tell cause my camera was moving so much.. i didnt see it until about hte red x because i was chatting.
we were standing in a parking lot by the airport where it was darker ..we waited for about 20 min from 950 pm so we had a good view ...i couldn't tell if there was any arc just flew straight towards us and to the left of us we were facing south west
 

Mick West

Administrator
Staff member
This panorama photo I took years ago shows planes traveling in straight lines. They look straight to the naked eye, but in wide angle they look curved.
trip-pano-w.jpeg
 

Inti

Active Member
Sorry its a bit late maybe I'm just not getting it ....Where is the sun right now to light up the ISS ....the suns rising in Europe right now
For an exact mathematical answer to that I'll leave it to someone more expert, but roughly, the sun is to one side "peeping" over the curve of the Earth, hitting the ISS because it is 270 miles higher than your position on the ground.

Have you ever watched the sun setting opposite a mountain? You can see the band of darkness rising up the side towards the peak, as the earth's curve rotates upward, cutting off thelight rays until only the topmost pinnacle are still lit by the reddish light. Now imagine that the mountain was 270 miles high. See how its peak would still be lit by the sun long after it was dark at ground level?
 

Inti

Active Member
That doesn't look to real .......and it didn't arc in our line of sight ...it flew across the sky ....
Well, we haven't got much else to compare such a sight to, to judge what "real" should look like. I think the reason why you didn't see a curve is that you were looking almost straight up at it, in more or less the same plane as the orbit.

If I point straight ahead and raise my straight arm back over my head, the line my fingertip draws on the ceiling is amost straight from my point of view, even though someone else would see it was a curved line when viewed from the side.
 

Hevach

Senior Member
That doesn't look to real .......and it didn't arc in our line of sight ...it flew across the sky ....
Those videos are both taken with fish-eye lenses designed to capture an extremely wide angle of the sky. They heavily distort lines.

The longest ISS pass possible is just around 5 minutes out of a 90 minute orbit, meaning you'll only see about 18-20 degrees (5%) of its orbit.
 

Mick West

Administrator
Staff member
For an exact mathematical answer to that I'll leave it to someone more expert, but roughly, the sun is to one side "peeping" over the curve of the Earth, hitting the ISS because it is 270 miles higher than your position on the ground.
The ISS is roughly 250 miles (402 km) above the ground, but varies by a mile or so as the orbit decays and is reboosted.

But yes, the tilt of the Earth and the angle of the ISS orbit complicates things, but you can simply say that while half the earth (50%, or 180 degrees) is in darkness, the ISS is only in darkness for 39% of a day, or about 78% of the night. So for 22% of the night the ISS is in full sun.

Here's a scale diagram illustrating this:
20160729-071000-4i14u.jpg
You can verify the scale, and experiment with it here:
https://www.geogebra.org/o/TBfymCaz
 

Mick West

Administrator
Staff member
The actual time the ISS spends in light (and visible from the dark side of the Earth) varies. Have a look at the orbit of the ISS:
Source: https://www.youtube.com/watch?v=2Rc3rh9o-QE

The circle and light band show where it's visible from. Now if you picture the earth being lit from one side or the other, the ISS can effectively by flying almost directly along the terminator (the boundary between light and dark), and so be lit by the sun for nearly all of its orbit.

http://www.skyandtelescope.com/observing/celestial-objects-to-watch/space-station-frenzy/
ISS-orbit-in-May-1.jpg
We are only a couple of months past mid May, so still quite good viewing opportunities.

And of course, all this only works on a globe shaped Earth. And since it does work exactly as predicted, for multiple simultaneous observers, then that proves the Earth is a globe.
 

Mackdog

Active Member
If it helps any, I have talked with astronauts face to face that have been on the space station, it is real, they are real, and I'm not making any of this up. The earth is round.
 
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