One thing to remember is with any lens shooting stars, you can only expose for so long before the rotation of the earth becomes apparent. When that happens you'll get star trails, IOW in your photo the stars start to elongate. The only way to avoid this is to have a tracking mount, which I'll assume you don't have. However you can still get very good results with just your camera and a sturdy tripod. For examples you may want to look thru this thread. Good luck and post back in the Astronomy and Celestial photo sharing section
There is a way to find out how long you can expose with a given focal length before you'll see star trails form, this formula will cover full frame and 1.6 crop bodies.
divide 600 by the focal length of the lens = maximum number of seconds before star trails form, for a full frame camera body.
For a crop body first convert the lens to the full frame equivalent; ex. 14mm lens x 1.6 = 22.4mm
600 / 22.4 = 26 seconds