One thing you have to understand is night shots like this are totally different than daytime shots . The longer the exposure the more stars you will capture . There are ways to bring out more stars but over processing can ruin the image . You can also try using a higher ISO but then your looking at more noise . Stacking multiple images helps reduce noise when flats and blacks are added but for this type shot the more you stack the more star trails you will have . Just keep practice with different exposures , ISO and f/ settings. If you have a setting on your camera for night shots without flash , give it a try and if the image looks good then compare the seetings the camera used for the image . I have that setting on my XSi and what i find is it will expose long enough to capture the amount of light and data that the cameras brain thinks it needs for an image . Most my images this way will be from 15-25 sec exposures depending how dark the sky is or how much LP you have in the area . When you find the setting you like then experiment with that same setting in manual mode and adjust accordingly to your taste . BTW i also like the shot above , looks like exposure time was set just right but i would be curious what raising the ISO would look like for the same settings .