Home > Ephemeris Program, Observing, The Moon > 04/23/2021 – Ephemeris – The gibbous Moon tonight

04/23/2021 – Ephemeris – The gibbous Moon tonight

April 23, 2021

This is Ephemeris for Friday, April 23rd. Today the Sun will be up for 13 hours and 53 minutes, setting at 8:38, and it will rise tomorrow at 6:43. The Moon, halfway from first quarter to full, will set at 5:49 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 upper left edge of the moon near the terminator is a bright spot visible in binoculars. In a telescope it is a crater called Aristarchus. It is a fairly new crater, probably 450 million years old. As a rule the brighter the crater the newer it is. Aristarchus is the brightest spot on the moon when it is seen during a full 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. They may be different for your location.


The Moon tonight
The Moon as it might be seen in a small telescope tonight, April 23, 2021 at 10 pm. Created using Stellarium.
Aristarchus close up
The impact crater Aristarchus, in the center, is 24 miles or 40 kilometers in diameter and approximately 450 million years old. Credit: Lunar and Planetary Institute.

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