Mare Nectaris is a classic example of a multi-ring basin on the moonThe week of September 12-18 takes us from Lunar Day 18 to Day 23. This week we will highlight the lunar sea called Mare Nectaris, viewable late Tuesday night.

The Nectaris basin was excavated 3.9 billion years agoMare Nectaris: [SE/L13; L=36°E] The Nectaris basin was excavated 3.9 billion years ago. The oldest features on the Moon formed prior to this event. Mare Nectaris is a classic example of a multi-ring basin. Tonight or tomorrow night will reveal Rupes Altai, a high cliff that is a conspicuous fragment of one of the original rings. As the shadows change, try to locate hints of other ring features surrounding Mare Nectaris.


On Thursday, the Pleiades star cluster will be 3° north of the Moon, and on Friday, Mars will be 4° south of the Moon.


It is highly recommended that you get a copy of Sky and Telescope’s Field Map of the Moon, the very finest Moon map available for use at the telescope. It is available for $10.95 at and on Amazon. All features mentioned in this blog will be keyed to the grid on the Field Map and will look like this: Plato: [NW/D9]

Courtesy of Gray Photography of Corpus Christi, Texas
Lunar photos: NASA / USGS / BMDO / LROC / ASU / DLR / LOLA / Moon Globe. Used by permission

Andrew Planck

Andrew Planck

Author and Astronomer Andrew Planck shepherds you to the moon and its mysteries of intrigue and surprise. Learn about the moon’s most fascinating objects, understand how the moon was formed and the names of many of the craters … and why they honor individuals who have changed the course of history.
Andrew Planck
Mare Nectaris: Lunar Sea and Multi-Ring Basin on the Moon
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