Iridium Satellites

Does never happened to you to lift your head towards the stars and see a light appear, then disappear a few seconds later? It was certainly a satellite.
What is Iridium?
Iridium is a satellite of telecommunications (they are only 66). They are placed on low orbit (about 780 km). They weigh 690 kg at launch and they have large solar panels.
What are the Iridium flares?
These are "astronomical" phenomena producing a sort of flash in the sky. In fact, this flash is due to the reflection of sunlight on solar panels for Iridium.
How to observe the Iridium flares?
First you must know that these phenomena are very short (4 to 5 seconds) and therefore we must be willing (specifically set your watch) and see the sky concerned. These phenomena are very bright, they go up to magnitude 8, 9, is 100 times brighter than Venus. So if the sky is clear and that you meet about the rules above, you should not miss!
To find the ephemeris on Iridium, go on Heavens above, an excellent American website, which gives you all the information necessary to observe the Iridium, depending on your position.
TIP For OBSERVERS
To do this, set your watch on the legal time in the second. You can call the speaking clock, or listen to hours tops on France Inter. There are also radio controlled clocks, in this case, time is continuously adjusted from a radio transmitter.