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Comment by tjbrennan | Hacker News Reader

Iridium flares are a really neat night sky phenomenon to look for. The predictions can be found on satellite tracking sites [1]. I caught one by accident when I noticed a satellite passing overhead on my way to my car one night. Over the next few seconds it increased to dazzling brightness, and then it disappeared just as quickly. I couldn't believe my luck.

[1] http://www.heavens-above.com/IridiumFlares.aspx

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You are very lucky. I had a script scrape that site (not sure if I broke their TOS) and send me an SMS about 5-10 minutes before a visible pass of something bright including Iridium flares, but I found that even if you know the exact time and direction of where it will happen it is still easy to miss it. It's very nice to see one when you do. If the sky is dark you can often see the satellite before and after it goes bright, but I've seen one shine through a blue sky which must be perplexing to spot by accident by people who don't know about these.

I once saw one accidentally, when I was lying in a garden around 03:00 just watching stars. Checked at HeavensAbove afterwards to confirm I haven't just imagined it.

I used to do a lot of Iridium hunting in high school, sometimes waking up at 04:30 to spot the morning ones (which, given that I also stayed up/was waking up early sometimes to watch Shuttle launches/landings on NASA TV - in my timezones they were often in the middle of the night - pretty much ensured that I was often quite sleepy at school).

I thought this was pretty interesting (http://www.heavens-above.com/IssHeight.aspx?) The mean height of the ISS over a two year period.

I had no idea that atmospheric drag had that great an effect at a 400km altitude.

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