Check out this site (linked below) for the scheduling of “Iridium Flares” in your area. You’d need to enter in your location, the more precise the better.
Some of these flares are incredibly bright, up to negative 8! However, most I think are around -2 or -3.
From their site...
“The Iridium satellites are relatively small telecommunications satellites in a low Earth orbit. They are part of a world-wide system for mobile communications operated by the Iridium LLC Corporation. When complete, there will be a total of 66 satellites in 6 orbit planes, at an altitude of around 780km.
As can be seen from the diagram opposite, each satellite has three main mission antennas (MMAs), which are flat, highly reflective surfaces, that can reflect the Sun’s rays to an observer on the ground when the geometry is correct. The satellite’s attitude is controlled so that the long axis remains vertical, with one MMA always pointing forwards.
Given this knowledge of the attitude, together with the orbital position of the satellite and the Sun and observer’s location, it is possible to calculate the angle between the direction to the observer from the satellite and the line of a perfect reflection of the Sun. This is the so-called “mirror angle” and determines the magnitude of the flare.
An Iridium Flare The photo on the right of two Iridium flares was taken by Porter Kier on January 11th, 1999. It shows Iridiums 20A (Mag. -2) and 22 (Mag. -7) above the Chesapeake Bay, Virginia area. For more information on the photo, and a full size version, just click on the image.”
Scroll down their home page to Satellites—> Iridium Flares for the scheduling. Again, enter your location first!
Wow, amazing info about the upcoming Iridium flares by geo! Right down to the fact it will be caused by the right antenna. Is it a quick glint? The site does not give duration. The next one in my area is Mag 1 whichnis rather dim, isn’t it?
I use the Sat track app myself. Does just what I need.
Over the years of observing them, what I have found was that the brighter the flare, the shorter the period.
In other words, if it is a -8 flare, you will see just a short glimps of the satellite. If it`s only a -1, you can pick it up juch sooner and follow it longer.
They are interesting to watch, but, sometimes interfere with deep sky observing