International Space Station

The International Space Station (ISS) can often be seen in our skies. It orbits the Earth roughly every hour and a half, but the Earth is spinning underneath it so it will only be above the horizon about 4 times per day. But to be visible it also has to be out of the Earth's shadow that is caused by the Sun and this usually means one viewing per day, sometimes two, for a few days and then a week or so without any sightings.

The Heavens Above website gives details of when you can see the ISS - I'm pretty sure it is always after sunset or before sunrise. All you need is your location - and Google Maps can give that very accurately, especially as you can centre the map on your garden. As I type (11th September) the ISS will be visible tomorrow (twice) and the next two days early in the morning and then on the 20th around 8:54. The length of time is very variable; on the 14th it's just 12 seconds, this morning it was nearly 4 minutes.

It looks like a very bright star moving about the speed of an aircraft. On 10th February it was due to appear, and being a Sunday I was at my mum's, so I tookmy telescope mount and camera and took a 30 second exposure of the area I knew the ISS would pass through. I took the telescope mount as that is motor driven so the stars wouldn't streak. Unfortunately I didn't get a good focus on the stars - but they haven't streaked. The bright line is the ISS as it passed across the field of view from right to left.

The brightest star is Aldeberan, an orange star (this was taken black and white) and one of the brightest in the sky. The V of stars to the right and above is the Hyades open cluster, which is also easy to see in winter. Many of the stars you can see in the photo wouldn't be visible to the naked eye.

Also on 10th February was an Iridium Flare. These are caused by sunlight reflecting off the antannae of these small telecommunication satellites. There are 66 Iridium satellites in orbit and the short, roughly 2 seconds, flares are easy to predict - and these are also on the Heavens Above website. Some can even be seen in daylight. As an example there are two tomorrow evening, one at 20:57 and as bright as Venus (3rd brightest natural object in out sky after the Sum and Moon) and another as 22:23 almost as bright as Sirius (brightest star). However if I was to drive 10 km to the west for the first or 50 km for the second then these would be over 4 times as bright as Venus.