In moist climates, water particles suspended in the atmosphere often condense on the front surface of the telescope's correcting plate. Such dew formation effectively ends an otherwise great night for seeing conditions. But the propensity for this to occur can be significantly be reduced by the addition of the Meade #678 dew shield, which is essentially an extension tube attaching to the telescope's front cell.
This device also effectively cuts down upon glare when you're using your scope for terrestrial observing in daylight conditions.