Tuesday, 10 July 2012

The stars at night

Hopefully most people realise that just like the sun, the moon and stars also move across the sky (apart from the pole star, which is fixed relative to the axis of the earth). So, if you capture an exposure lasting perhaps an hour or so, you will actually see the movement of the stars across the sky. This is what is called "star trail" photography.

There are two ways to do it: all the below were done using a single exposure, which has some drawbacks, as the colours can get very messed up by street lighting (even from lights miles and miles away), and the final image can be grainy. There is another way, involving stacking together multiple shorter exposures. The next time I see the stars (you know, if this rain moves away ever..) I might try the second method.

The stars are just visible beyond the treetops, which are lit by the light of a campfire.

This is not a trail shot: this was a high ISO 30 second image, giving a "star dust" effect. You can see the lights of London in the bottom right.. And this was nearly 40 miles out..

The same location, but an exposure of about an hour.

The Wey navigation at night, lit by London..

About two hours.