The International Space Station is now so large it is visible in broad daylight as a white moving dot in a clear sky.

While it has been capable of being seen while the sun is high in the sky for some time under the most perfect of conditions and with sharp eyes, the recent completion of the broad solar panels on the 108 metres by 73 metres city building sized ISS has made it much easier to spot.

And when another spacecraft is docked, during regular visits by the Space Shuttle, the Soviet supply and manned craft, or the European Jules Verne “space truck” it gets even brighter.

The space station is still gaining clip-on laboratory modules, with another made by Japan, due next month, but it is the huge solar panels that generate most of its brilliance.

Those panels are also springing surprises by “flaring” into an incredibly bright moving star without warning for several seconds if the angle between them, the sun, and observers on the ground just happens to become optimal.

If this happens at night, when the ISS is still illuminated by the sun, the flare is reported to be as bright as –11 magnitude, which is bright enough to cast shadows against a light surface like concrete, a pale coloured wall or sand.

This is far more dazzling than Venus (which is currently visible as the morning star) at its best, or the occasional flare thrown off an Iridium communications satellite when the sun is perfectly reflected of one of its highly polished antennas.

In Plane Talking later today I’ll publish a step by step guide for non amateur astronomers to accurately find opportunities to see the Space Station in broad daylight using the free Heavens Above resource.

( NOTE: The ISS appears well away from the sun in passes visible to the naked eye. Never, ever, look directly at the sun or anywhere near it with the naked eyes or even wearing sun glasses. NEVER.)