Dust and dew are two main concerns when maintaining a telescope. Dust on glass results in unclear images. So, its essential to store your telescope in dry places where it doesnt end up catching dew and stays dust-free. You can use a squeeze ball blower to eliminate the dust from the lens. You can also use diluted isopropyl alcohol to clean the lens. However, remember that dusty glass is far better than a scratched one. So, be gentle while cleaning the glass. Always cover the focus finder and lens with a dust cap or plastic cover when the telescope is not in use.