DSLR Basics - what exposure, aperture, ISO etc

Guys,
thanks for the helpful tips and replies. A lot of what you've said above is encouraging for me. As most of you will know, the hardest part is learning, but thats what helps the most.

Keith,
thanks for the quick breakdown tutotrial there. It all makes sense, and what you said about practise goes without saying. By the way, with regards to the types of lenses I have - I use Tamron, and was considered that they can rival the Canon for their own quality, but are more affordable, of course. I have not been disappointed by them yet.

Frank,
the fogging was more than likely haze at the time of that shot. For the most part, the stars in all the exposures were in focus. Dew was not a problem that night. I do have a lens hood which was being used. However, when shooting near the zenith, that's not going to be much use! Last nights further experiment showed that I'll get trailing at 10 seconds with this lens no problem.

John Murphy,
I like that polar shot. Whilst the centre was more exposed that the rest, it still has a nice soft pastel look to it. These kinds of shots I will also be taking. I think such star trail shots set against a landscape can be very dramatic. I didn't know about the darks subtraction feature, thanks for that. And each shot was taken using mirror lock-up and a remote cabel (thanks Dave Lillis!). I never thought about altering the white balance for astronomy shots.

Keep the comments and suggestions coming guys!

5. White Balance. I usually use Daylight setting, instead of the default Auto.

.

What difference to the image does this make John?

Frank,

White balance really describes how blue or red your whites will be - a bit like Daz. If you look at the camera settings you'll see that white balance is really a function of the lighting that the shot was taken in (Daylight, Shade, Cloudy, Fluorescent, Tungsten etc.). Each of these settings will alter the intensity of colours at different levels of the spectrum. Given that the defalt setting is Auto, and the lighting is provided only by starlight you'll be relying on the camera picking the correct WB for your shot, and although the 350D is pretty good at it, it can be fooled. The most realistic setting I think is Daylight. It's not a disaster if you don't change the setting, as if you are shooting in RAW, then the White Balance can be changed by Digital Photo Professional later.
Try it sometime with any RAW shot, change through all the WB settings and you'll see the difference it can make to shots. Shade will redden the picture, while Tungsten will make it bluer.

Thanks for that John, I'll give it a try sometime.