Last night I went out on to the Denbigh Moors in an attempt to get away from the light pollution and have a try at some Astrophotography. I know the area a little, as it’s where I played a little when I had a 4×4 car, and the place I always head for if I’m able where there’s a meteor shower. There is a little light pollution, but it’s the best area locally to me.
As I was setting up, I noticed almost directly overhead a very bright object moving at quite a rapid pace across the sky. Without doubt the ISS (I’d known from an earlier post on Twitter by @virtualastro that the ISS would be visible from the UK) and when I recognised it I simply stopped dead, tracing its movement right down to the point where it fell in to shadow.
I posted the fact that I had seen the ISS on Twitter, and one of my friends asked how to tell the difference between an ISS pass and, for example, a meteor or an Iridium flare. I couldn’t quite get it all in to 140 characters on Twitter, hence this blog post.
- A meteor usually moves very quickly across the sky, and is normally visible for only a few seconds.
- The ISS is bright. There will be brighter stars in the sky, but not many.
- The ISS travels the sky at a what I’d describe as a purposeful but measured speed. A typical pass would be in the 3-4 minute range.
- An Iridium flare typically lasts only a few seconds, and more often than not looks like a flashing object.
Of course if you really want to make sure you see the ISS, use a website like Heavens Above and make sure you’re out and have your eyes adjusted to the dark before the pass time.