MOON TOUR
POSIDONIUS CRATER
This impact makes for prime viewing this month
© NASA
One of the Moon’s most sublime and recognisable craters, Posidonius can be viewed to good advantage as it’s illuminated by a local evening Sun on the morning of 4 August, when the Moon is situated above the southeastern horizon. Two weeks later, the Moon lies low above the western horizon as the dusk skies are darkening, but vigilant telescopic observers may still be able to make out Posidonius near the lunar terminator despite the Moon’s low twilight altitude.
Measuring 95 kilometres (59 miles) across, Posidonius is a prominent crater that lies at the northeastern border of the large nearcircular Mare Serenitatis (Sea of Serenity) and at the entrance to Lacus Somniorum (Lake of Dreams), an irregular lava-filled plain that forms a short arc parallel to the northeastern shoreline of Mare Serenitatis. When illuminated, Posidonius is easily identified through small instruments, even steadily mounted 7x50 binoculars.