If you find yourself away from the big city, consider photographing star trails. You will need a programmable cable release that can be set for up to three hours, a tripod, a clear evening with little ambient light and a external power source for your camera if you are trying to capture an exposure longer than an hour. An exposure of twenty minutes will produce dashes of the star trails, for longer trails use longer exposures. Here are a few more things to consider:
• Try including foreground objects that could add interest to your star trails.
• Use ISO 100 to prevent digital noise, set aperture to f/3.2 to f/5.6 and be sure to set your camera a good distance from any foreground objects to keep them in focus along with the background.
• Time your shot for the new cycle of the moon or when the moon has not risen or has already set to keep the ambient light down.
• To avoid fogging of your lens in humid areas use a couple of chemical hand warmers: tape or rubber band them together around the lens. Tape down your focus ring and anything else that could move voluntarily on the camera body or lens.
For more information see Dan Heller’s page on star trails. http://www.danheller.com/star-trails.html/