When observing delicate deep-sky objects, what is the ideal lunar cycle condition?

Answer

During the New Moon phase, or when the Moon is below the horizon.

The Moon acts as a major source of natural light pollution. During a Full Moon, the ambient light can make faint objects completely invisible, so moonless periods are preferred.

When observing delicate deep-sky objects, what is the ideal lunar cycle condition?
weatherobservationskystargazingcondition