I try and shoot mine around f11- f16. Depending on the light, usually a 15-30 sec exposure.
If you are using a tripod, look into a remote release or use the 2 second shutter timer. Sometimes, just pressing the button is enough to set off some vibrations.
What was your ISO. It looks grainy to me. Set your ISO to 100 or so. and keep your shutter speed as fast at you can. It may still take afew seconds but keep it as short at you can.