Earthshine is a faint glow on the Moon caused by sunlight reflecting off the Earth, onto the Moon, and then back to our eyes. This creates a ghostly, full-disc view of the Moon, even when it's in its crescent phases. The best time to see Earthshine is typically during the spring, around the time of the waxing and waning crescents near a new moon. This year, the new moon occurs on April 17th, making the days surrounding it ideal for viewing.