I set my ISO to 800, which is the highest I dare go on my camera (before the noise becomes too upsetting) and started my vigil of constant fifteen second exposures, with eleven second gaps between shots while the camera did its processing. I stayed there for an hour, during which time the sky began to cloud over and the spire light went off. This is how it looked when I left:
The difference between the positions of the stars from the start of the hour to the end can be seen on these two photographs, but the sky really comes to life when all the images are put together in a sequence. This small video doesn't show the stars, (I'm having a little computer trouble today, but will repost when I've managed it) but does give an idea of the cloud cover that produces much of the orange glow in the final image:
There is something magical about star trail images and something so special about watching one appear on the screen before you. They are so easy and so fun and I can't wait to have another go!