Intervalometer and multiple images
 

In a recent edition of Digital Camera there was an image of a church and star trails. A built in intervalometer had been used and 70 images captured and used to produce the final image.

I had never heard of an intervalometer before but I can see that I could get one for my Canon 60D if I wanted to. However my main question is how do you process 70 images together. I cannot imagine Photoshop would manage so many images concurrently and I would suspect it would take a lot of processing from a PC.

You can do it photoshop but there are speciality packages written specially for this sort of thing. I think Registax & deep sky stacker are the favourites for astro purposes - and both probably have options for star trails.