Capturing images of the stars is a difficult, but rewarding, skill to master. You can use a mobile app such as StarWalk to locate where the galaxy (Milky Way) will appear in the night sky. It helps to choose a location that is far away from the light pollution around our cities and towns. Choose a night where the moon has not yet risen and remember to pack a torch and some warm clothes. The camera equipment and camera settings that usually give the best results is a wide-angle lens with an aperture of f/2.8 or wider (use the widest aperture). Set the ISO to either 3,200 or 6,400 and use a shutter speed of 20 seconds or longer. On most lenses the stars will not appear sharp at the infinity setting, so you need to take a test image, review the image at magnified view and then fine-tune the focus until a subsequent test image achieves sharp focus. Go to http://www.lonelyspeck.com for additional information.
This is an extract from Introduction to Photography: A visual Guide to the Essential Skills of Photography and Lightroom.