Determine your location in coordinates (latitude and longitude). You can use an online service.
Use a prediction program and input your coordinates to determine the time and location of an Iridium flare in your area. Heavens-above.com - online service that can predict Iridium flares as well as determine coordinates Find your location using one of the options listed. After submitting your coordinates, find a section that says, "Iridium Flares". Click on the "next 7 days" link, or the "next 24 hrs" link if you wish. Find an Iridium flare listed (the time listed is 24-hour local time). Write down the date, time, altitude, and azimuth. SKYSAT -- 16-bit graphical satellite prediction program that also indicates possible flares from Iridium and other satellites IRIDFLAR -- DOS based program
Recheck the prediction shortly before observing. Flares that are forecast days or weeks in advance might not be accurate, so they might be brighter or dimmer than expected, come earlier or later, be in a slightly different point of the sky, or sometimes not appear at all.
Make sure your clock or watch is tuned as precisely as possible, otherwise you'll likely miss it or be too early and think it's over. Some TV channels, such as some weather and news channels will list the time to the second. Some websites list time accurately, some in UTC and others in local time. The Atomic Clock in Boulder shows all U.S. time zones or UTC.
Go outside at least a couple of minutes before the time listed on the correct date. See if the sky is clear or at least partially clear, or else you will not be able to see the flare. This will allow you time to gauge the correct place in the sky to watch. Also, you can usually see the satellite as it approaches the 'flare' point if you're on-site a little early.
Look in the direction and altitude listed. An Iridium flare looks like a star that moves slowly and quickly brightens, then slowly fades away. If it looks elongated, leaves a visible trail, fades away in less than a second from becoming visible, or lasts more than a minute, it is most likely either a meteor, a fireball, or the ISS (International Space Station, which can also be found with similar methods). Azimuth - Measured clockwise around the observer's horizon from north; north has an azimuth of 0°, east 90°, south 180° and west 270°. Altitude - Overhead is 90°, directly in front of you is 0°. Determining the correct altitude to watch is a bit more difficult than the azimuth, especially in the twilight before stars begin to appear, which is the usual time satellites are seen. A handy gauge is your fist held at arm's length - it is approximately 10° 'tall'. You may prefer to also extend your index (pointer) and pinky fingers straight out (not 'splayed') to provide a better 0° and 10° gauging point. Place your extended pinky on the horizon in front of you, look up to your index finger and note where it is against the sky -- count "10". Keep your eyes on that spot, and shift your fist upwards until the pinky is where the index was - then up to the index's new position and count "20", and so on. Repeat until you've determined the correct angle - and of course, a 5° (eg, 45° etc.) position falls in the middle between the extended fingers. This 'gauge' is pretty accurate. You can continue up to 90° & if that point is directly overhead, you're doing it correctly.
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