Use of a tripod is recommended for night landscapes. Shots may be affected by camera
blur even with a tripod. There are a variety of techniques for reducing blur.
(1) Use an optional wireless remote control. Pressing the shutter-release button can actually be enough to cause blur; using a remote control helps you keep your hands away from the camera.
(2) If this doesn't solve the problem, try using mirror-up mode. The movement of the mirror inside the camera can sometimes blur your shots; in mirror-up mode, the mirror is raised before the shutter is released, keeping camera movement to a minimum.
You may notice "noise" (image artifacts) in long time-exposures taken at shutter speeds of "bulb" or "time". This can be addressed by using long-exposure noise reduction.