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Iridium Flares

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Iridium satellite One of the more interesting lights in the sky come from a series of communication satellites called Iridium.  These satellites have an antenna that is similar to a dressing mirror in size, shape, and reflectivity.  So what?  Well, from 485 miles up, if that mirror is aligned just right, it will reflect the sun towards you, becoming the brightest thing in the sky.  In astronomical parlance, these Iridium Flares can be as bright as magnitude -7 (brighter than Venus ever gets).  They last for only a few seconds at a time.

So, how do you know when and where an Iridium Flare will happen?  Well, there's an excellent web site called Heavens-Above that will happily calculate the Iridium flare schedule for any place on Earth.  You can go to their site (which can also show you when ISS and many other satellites will be overhead), or you can check out the schedules for San Diego or Los Angeles.  Note that the more precise you are about your location, the more accurate the flare prediction will be.

Heavens-Above now has an excellent tool that lets you nail down your latitude and longitude quite precisely.

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