If you’ve never seen the International Space Station in orbit, you’re missing out on something awesome. Oh, you don't have a telescope? No problem, the ISS is easily visible at night. True. It looks like a very bright star that moves across the sky for a few minutes. You just need to know when and where to look, and you can find out on a site like Spot the Station or Heavens Above. They’re both great.

OK, so now that you’ve looked up the time and date of the next ISS pass (hopefully you have clear skies), how about we measure the speed of the space station using a smartphone. Actually, I'm only partially confident this will work. Oh, we’ll get a value, but we’ll have to double-check that the phone does what I think it does.

Here's how this will work: I'm going to use Night Mode on my iPhone 11. As far as I can tell, Night Mode increases exposure time in the dark, so as to collect more light. Why don't all phone cams do this? Well, it's not so simple. If you just pull out your phone and take, say, a 1-second exposure, it's going to look like a blurry mess. No matter how hard you try to hold still, your hand is going to move.

So I think there are a couple of other things happening as well: The phone probably measures your hand's movement using an accelerometer (here’s a whole post I wrote about that). And it likely uses some type of image-stabilization software to compensate for that movement. (Of course, you could use a tripod instead, but you probably don't have one of those in your pocket.)

Here's an example of a Night Mode photo, taken from my backyard at night. Trust me, it was pretty dark, but the picture turned out nice.

Photograph: Rhett Allain

Lining It Up

Now let's put this together with the ISS. What happens if you try to take a Night Mode shot of the space station as it goes overhead? It looks like this: