Home > Ephemeris Program, Observing, The Moon > 05/29/2023 – Ephemeris – Sinus Iridium, a hook into night

05/29/2023 – Ephemeris – Sinus Iridium, a hook into night

May 29, 2023

This is Bob Moler with Ephemeris for Memorial Day, Monday, May 29th. Today the Sun will be up for 15 hours and 16 minutes, setting at 9:18, and it will rise tomorrow at 6:01. The Moon, 2 days past first quarter, will set at 3:41 tomorrow morning.

Let’s look at the Moon tonight. One of my favorite formations is coming into light. It is called Sinus Iridium or Bay of Rainbows. Sorry, there’s no color here. But if caught at right time, and tonight’s the night, this ruined crater will appear as a hook out into night off the upper left edge of the moon. Officially it’s a bay to the Sea of Showers or Mare Imbrium. The north edge of the bay are mountains called the Jura Mountains. The south edge disappears into Mare Imbrium. The floor of the Sinus Iridium is about twelve hundred feet lower than Mare Imbrium. The transition is gradual because it isn’t very noticeable. The formation is large enough to be seen in binoculars. Sinus Iridium is 242 miles wide, a good tenth the diameter of the Moon itself.

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 northern (upper) part of the Moon tonight, May 29, 2023, at 10 pm. showing the Jura Mountains jutting into darkness at the morning terminator (sunrise line). Click or tap the image to enlarge it. Created using Virtual Moon Atlas, LibreOffice Draw and GIMP.
Categories: Ephemeris Program, Observing, The Moon Tags: