The Moon
The Moon is the easiest night sky object to study. With our without a telescope, it can be studied simply by looking up when it is out on a clear sky. Without a telescope, its phases and its position relative to other objects in the sky can be tracked from night to night. With a telescope, its features pop out with remarkable clarity. It is also completely unaffected by artificial light pollution. In fact, for deep sky observers and imagers, it IS a source of light pollution when it's up and about!