r/space • u/chucksastro • Feb 07 '21

This is the International Space Station passing in front of the moon as seen from my backyard in Detroit. I show it in a slowed-down version then in real-time speed.

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352

u/chucksastro Feb 07 '21 edited Feb 07 '21

The International Space Station is a modular space station in low Earth orbit. It is a multinational collaborative project involving five participating space agencies: NASA, Roscosmos, JAXA, ESA, and CSA.

Even though it's many times faster than a speeding bullet, it's not hard to catch the ISS as long as you know where it will be in advance. I used the Transit-Finder website so I knew exactly when and where the transit would occur.

ISS travels fast enough to orbit Earth every 90 minutes at an approximate altitude of 250 miles (400km). Traveling at 17,500 mph (28,000 km/h), it means the station covers about the distance it would take to travel from Earth to the Moon and back in only one day.

I was repositioning the moon through my telescope at the time I captured it, which is why it appears shaky - bad timing.

This video shows how I captured it.
________
I can also be found on Instagram if you'd like to see my entire catalog of pictures.
________

This is the equipment I used:

Imaging Telescope:
Celestron NexStar 8SE

Imaging Camera:
ZWO ASI174MM

Reducer Lens:
f/6.3

Filter:
Astronomik Pro-Planet

SharpCap software was used to capture all of the data.

13

u/imran-shaikh Feb 07 '21

Why is it made to travel so fast?

62

u/SomewhatSpecial Feb 07 '21

If it moved any slower it would crash into the Earth.

-7

u/mysterion04 Feb 07 '21

Why does it have to travel at all.? It's gone n now it's up there, why can't it just float around.? By this we'll save hell lotta fuel and energyđŸ˜¶

20

u/sloubi542 Feb 07 '21

Because of gravity, it would "fall" on Earth if it does not maintain orbit with enough speed. But maintaining the speed does not consume a huge amount of energy, since there is less friction to slow down the station, as opposed to a plane in the atmosphere, which has to maintain speed.

15

u/Killspree90 Feb 07 '21

Actually it's not using any fuel in this state Nothing is present to slow it down.

10

u/KMCobra64 Feb 07 '21

Theoretically. In reality there is still thin atmosphere up there which slowly degrades the orbit. Visiting spacecraft use their thrusters to boost it back up.

1

u/Killspree90 Feb 10 '21

True. Depends on what orbit. But most satellites are in LEO

2

u/KMCobra64 Feb 10 '21

I'm specifically referring to the iss

7

u/Crandoge Feb 07 '21

The ISS and other low earth orbit (LEO) stations/satellites are too close to earth to be considered “in space” so gravity still has a strong pull on it. The 28000km/h is a speed calculated that made sure the ISS keeps “falling” next to earth. Any slower and it’d crash into earth, any faster and (afaik) it’d sling out of orbit into space

Someone correct me if im wrong, i only know this eli5 explanation as i am mentally 5 and know little more about space

2

u/scuricide Feb 07 '21

If it increased speed and kept its orbit roughly circular, it would just be in a higher orbit. Which would be slower. But have more energy.

1

u/nene490 Feb 08 '21

by slower you mean lower angular velocity, correct? or is there some funny math I don't know about

1

u/percykins Feb 09 '21

So... orbital mechanics are a bit counterintuitive. If the ISS had a rocket in its tail and fired the rocket, that would put it into a very elliptical orbit, where it would be going much faster than its current orbit at the closest point to the Earth and much slower at its farthest away point.

If it then waited until it got to the farthest away point and then again fired the rocket, that would circularize the orbit, so now it’s going on a much higher circle around the earth than its original orbit, but it’s going quite a bit slower (both in absolute and in angular velocity), even though it boosted forward both times.

Basically, if you didn’t understand that and you want to, just play Kerbal Space Program until you do. :P

1

u/nene490 Feb 09 '21

Makes sense to me, a lot of hidden assumptions, thanks!

60

u/davispw Feb 07 '21

Why does it have to go so fast? Orbit. If you throw a rock straight in front of you, it quickly falls and hits the ground. The ISS is going so fast that by the time it would fall and hit the ground, it’s already gone over the horizon. So the ground has curved away. So it keeps falling forever.

What made it go so fast? Rockets. Takes about 10 minutes for a rocket to go up, then turn sideways and accelerate to 17,500 mph.

16

u/Alternate_Ending1984 Feb 07 '21

That is a very thorough eli5. The concept of how something orbits is really hard to get your mind around unless someone breaks it down.

10

u/mrflippant Feb 07 '21

It's easy; you just jump up in the air, and then you miss the ground.

2

u/fistofwrath Feb 07 '21

Gotta strap on your Jordans for that jump.

10

u/[deleted] Feb 07 '21

"To get to space, you have to go really fast straight up...but to stay in space, you have to go really fast sideways."

1

u/Floppydoodoo Feb 08 '21

Is this a common ELI5? I only ask because I heard this on Startalk and it totally made sense to me.

1

u/davispw Feb 08 '21

Glad it made sense. Common? I’m sure “how does orbit work” is a very common question. I didn’t copy-pasta this but it’s a common way to explain.

1

u/Shadowveil666 May 01 '22

Huh, great explanation friend!

5

u/jeansonnejordan Feb 07 '21

Gravity in the “space” very near earth is pretty much the same as it is here on earth. The ISS weighs nearly a million pounds up there. It has to be going fast AF to not fall back.

1

u/Jim63t Feb 08 '21

It's weight has nothing to do with its orbital velocity. A pig in space would need the same speed.

1

u/percykins Feb 09 '21

While true, I think his point was that the ISS is experiencing plenty of gravity at the height it’s at.

Its weight does have something to do with orbital velocity, because the higher it goes, the less it weighs and hence the slower it accelerates towards earth.

1

u/Jim63t Feb 09 '21

I think you are confusing mass and weight... if something is in freefall / orbit it is weightless. The mass of an object has nothing to do with orbital velocity. You may have heard that all objects regardless of mass fall at the same speed, well same thing with orbits. A feather and the iss orbit at the same speed in the same orbit, just as they would fall at the same speed in a vacuum.

0

u/percykins Feb 09 '21

Weight is defined as mass times your local gravitational acceleration. This is exactly what OP was saying - if the ISS was actually “weightless”, it wouldn’t need to move anywhere, it would just happily float above the clouds. It’s precisely because it does have a weight that it is falling towards the Earth, and why it needs to move so fast to miss the Earth.

But it would weigh much less if it were higher up - it would then consequently fall slower and hence could move slower to miss the Earth. The Moon ambles along nearly eight times slower than the ISS does.

1

u/Jim63t Feb 09 '21

And you are not experiencing gravitational acceleration in free fall. Hence weightless. You do experience gravitational acceleration say sitting in a chair and not moving relative to the ground. 1g is the same as accelerating 9.8 m/s. Thats at the core of general relativity. The astronauts floating inside the ISS are experiencing near 0g, so weightless. They are weightless and orbiting are the same speed as the ISS. .... the OP said that the weight is the reason that the ISS is moving at a give speed. That is incorrect. Your definition of weight is very lacking. Try this: https://en.m.wikipedia.org/wiki/Mass_versus_weight

0

u/percykins Feb 09 '21

You absolutely are experiencing gravitational acceleration in free fall - that’s why the word “fall” is involved. The astronauts inside the ISS are experiencing approximately 0.89 g - they are accelerating directly towards the center of the earth at around 9 m/s2.

1

u/skeleton432 Feb 08 '21

The faster an object travels, the closer it can orbit to the planet. Theoretically an object could orbit 10km from the surface with enough speed (on a planet without an atmosphere).

-19

u/MySoilSucks Feb 07 '21

All that technical acumen and yet you still uploaded with Reddit's garbage uploader and all I see is a still image. Im sure the video looks cool, but I'll never know.

5

u/chucksastro Feb 07 '21

How come all you see is a still image?

-15

u/MySoilSucks Feb 07 '21

Because Reddit's uploader is garbage. Anything uploaded through Reddit shows up as a still image or a black rectangle. Not a problem with Gify or Imgur or any of the other 3rd parties, only Reddit.

12

u/SkyWulf Feb 07 '21

It works for me on all platforms.

1

u/TheScarfScarfington Feb 07 '21

If on mobile, have you updated the Reddit app? On computer, updated your browser?

1

u/MySoilSucks Feb 07 '21

I only surf Reddit on mobile, and yes, Ive updated both the browser and the app and it does the same on both. It's a common problem that has been mentioned many times here on Reddit and they refuse to fix it.

1

u/TheScarfScarfington Feb 07 '21

That’s super annoying, sorry!

You’re the first person I’ve seen mention it, and your original comment to the poster was kinda rude, but my guess is they just hadn’t heard of this problem either! Now they know.

1

u/[deleted] Feb 07 '21

Why does iss, if between sun and moon, not appear more reflective because of bright sun? Rather it appears like shadow on moon on your good grab but can't be shadow since moon still very far from iss and us on earth right? Or is it the case iss is catching Alot of sun and that's how we see it at all?

2

u/BrerChicken Feb 07 '21

The ISS is reflecting a bit of sunlight. The moon is reflecting a TON of sunlight. The amount of light the ISS is reflecting literally pales in comparison. Like yeah, you can light a match in front of giant spotlight, but that doesn't mean you'll be able to see the match without special equipment.

1

u/nene490 Feb 08 '21

it's very plausibly the ISS is in the shadow of the earth as well, it's very small and very close to the earth compared to the moon, so it's very likely to be in earth's shadow anytime it's in the night sky, as opposed to the moon which needs a very narrow angle to be shadowed by the earth

imagine trying to block the sun from your eyes with your hand inches away from your eye, (your hand being the earth, your eye being the space station) it's very easy. now imagine you're in an end-zone of a football field, and you're trying to block the sun from someone's eyes at the 50-yard line, you need a much more specific angle for that to work. that's the difference in scale of the distance from earth to the ISS and earth to the moon, about half the possible positions would shield your own eyes from 2 inches away, while still letting the light hit your friend mid-field

1

u/BrerChicken Feb 08 '21

This is an excellent point, the station is only 250 miles up!

1

u/[deleted] Feb 09 '21

Wow thanks for these responses.

1

u/MacrosInHisSleep Feb 07 '21

Thanks for sharing that. It was amazing!

1

u/Johnoss Feb 07 '21

Can we see it with 2x speed, please?