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Ephemeris: 07/18/2024 The brightest spot on the Moon

July 18, 2024

This is Ephemeris for Thursday, July 18th. Today the Sun will be up for 15 hours and 7 minutes, setting at 9:22, and it will rise tomorrow at 6:15. The Moon, 3 days before full, will set at 3:40 tomorrow morning.

The moon tonight is bright. The sunrise line or terminator on the moon is crossing the large gray plain called Oceanus Procellarum, the largest of the moon’s seas. These seas were figments of the first telescopic observer’s imagination. They are really huge impact basins into which interior lava flowed. On the left side of the Moon is a bright spot in the gray expanse of Oceanus Procellarum visible in binoculars. In a telescope it is a crater called Aristarchus. It is a fairly new crater in lunar terms, probably less than a billion years old. As a rule the brighter the crater the newer it is. Aristarchus is the brightest spot on the Moon. Over the years visual astronomers have seen hazes and bright spots from time to time in and near Aristarchus.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT–4 hours). They may be different for your location.

Addendum

The Moon as it might appear at 11 PM tonight
The Moon as it might appear at 11 PM tonight, July 18th 2024. Annotated are Oceanus Procellarum and the crater Aristarchus. Created using Stellarium, LibreOffice Draw, and GIMP.
Aristarchus close up
The crater Aristarchus in a telescope from Earth. To the left of Aristarchus is Vallis Schroteri or Schroter’s Valley ending with the crater Herodotus, which is nicknamed the Cobra Head. They are visible in small telescopes. Credit: Lunar and Planetary Institute.
Oblique view of the crater Aristarchus from a lunar orbiting satellite
Oblique view of the crater Aristarchus from a lunar orbiting satellite. Credit: NASA/GSFC/Arizona State University.
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