Full Moon immersed in a layer of thin high clouds while rising after a penumbral lunar eclipse on 5 May 2023. A penumbral lunar eclipse occurs when part or all of the Moon travels through the outer, fainter part of the Earths shadow, or penumbra. This type of lunar eclipse is much more subtle and more difficult to observe than a total or partial eclipse of the moon. The penumbra causes a subtle dimming of the lunar surface, which is only visible to the naked eye when about 70 percent of the Moons diameter has immersed into Earths penumbra. Image captured from the Dark Sky Alqueva Observatory in Portugal.