Ephemerides
From chi and h
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Ephemeris (plural ephemerides) is the term for astronomical forecast data, such as where each planet is, how bright it is, when eclipses occur, etc.
International Space Station ISS/Zarya
The International Space Station is also known as Zarya (Russian for dawn), since its first module was build and launched by Russia. While in sunlight, it is very bright (about -3 mag according to http://www.heavens-above.com) and easy to spot at night. Like most satellites it orbits west to east. In an evening pass, it will rise in the West or Southwest and move eastward. Usually it will then disappear into the Earth's shadow so that we cannot see it setting in the East or Southeast. In a morning pass it moves in the same direction, but the shadow is on the other side. So it will emerge from the shadow and move toward its set on the east or southeast horizon.
Chinese space station Tiangong 1
This satellite was launched in September 2011 and reaches a brightness of about 2.5 mag. The inclination of the orbit is less than Zarya, so that in Edinburgh it will rise no more than 6° above the horizon.
Iridium flares
There are about 90 Iridium satellites in Earth orbit, which are intended for satellite-based mobile phone communications. These satellites have become famous for the fact that they can produce very bright flares. These occur when one of their three large'ish flat'ish aerials happens to reflect the sunlight onto the observer. These aerials point 40° downward from the orbit onto Earth, one points in the forward direction the other two point back left and back right.
For any given time and using the satellite orbital elements from http://www.celestrak.com one can calculate where the Sun, satellite and observer are, and by how many degrees the reflection of each of the three aerials misses the observer. An empirical relationship between this angle and the brightness of the reflection has been determined (Randy John, 2002, SKYSAT v0.64, http://home.comcast.net/~skysat). 2° corresponds to about 0 mag, 0.5° to -3 mag. The brightest flares are -8 or -9 mag.
These are flares and not flashes. A nighttime flare lasts about 10 to 30 s, during which time the satellite moves several degrees. With a precision of about 1 s, I calculate here the time of maximum brightness of a flare, and also the times when the angle is 2°. I do not check whether it is day or night. You have to make your own judgement. The brightest flares should be visible even in daylight, perhaps those brighter than -5 mag or so.
I re-calculate each day, around midday UT, for the next 24-hour interval. The calculations are for Edinburgh. To give an idea of how far away from the city they remain valid, consider a a typical distance of the satellite of 1000 km and a typical elevation of h = 40°. At that distance the 2° angle corresponds to 35 km. If you're in the ideal spot and looking at the satellite, and then go that far sideways, you lose the flare. Forward or backward you can go further by a factor 1/sin(h). Unfortunately, my calculations don't tell you which way to go to have an even brighter flare. But these flares are common enough that you usually don't need to travel to catch one.
If you're not near enough to Edinburgh, or if you want more information about the flares that hit you, try http://www.heavens-above.com. There you can pick a place and get a longer and more detailed forecast.
