The great thing about shooting starsis you can really push the photo in post processing (using RAW) without many issues at all. For example this:
Was shot at f/2.8 for 30s at 17mm with an ISO of 3200 (I thinK) but then pushed a lot in photoshop. The other option to do is to blend multiple exposure together, for example this one:
Was a stack of 34 images at f/4, 30s and ISO 1600 then pushed a little in Photoshop. I used a program called
startrails.de to do it, free, easy to use and small program you can download.
However bear in mind light pollution in both these areas was non existent and the sky was very clear, the first shot in North East Costa Rica, the second shot in Death Valley California. It's a lot harder to get that kind of shot in the UK, however not impossible, there are plenty of places in Cornwall and to a lesser extent Devon as well as places like Snowdonia and a significant part of Scotland (away from habitation). If you live in the South East you're basically ******* unless you travel a long distance. HOWEVER you can always try and get some star trail images, much easier to do with light pollution. For example
Although they aren't the best pictures to show as they were shot in Maine and Death Valley again, I do however have a couple shot in the middle of towns with some nice trails however they don't seem to be on my flickr stream so I'll have to find them. For those sort of shots you can use similar settings as above, although I'd reduce the ISO a little, then you shoot for as long as possible and take multiple exposures then merge them together using Startrails.de. In a heavily lit area you're probably looking at
100 30 second exposures to get a shot*, in an area like the above, maybe
30+ 2 minute exposures. Both photos were shot using a 12-24 at
12mm at F/4 and ISO 200.
What I also find useful is to try and adjust the exposure length to that of the foreground, exposure length is the important bit for getting the foreground shot right, the aperture and ISO for the stars. I also then usually process the foreground as a separate "image" and overlay it on the star shot. By that I mean send all the photos shot to startrails.de, let it do it's blending and stacking, import the final TIFF it produces into photoshop and adjust if to get the best sky image. Then I go back to one of the original RAW files and adjust the image for the foreground, just like you would for a normal photo, then mask the sky out of that image and overlay it over the foreground of the stacked sky adjusted image.
Ok so this was meant to be a short post with a couple of suggestions... Got a bit long but hopefully it's a little helpful.
Thanks ..
