Bob Moler's Ephemeris Blog

Ephemeris for Tuesday, September 25th.  The sun will rise at 7:33.  It’ll be up for 11 hours and 59 minutes, setting at 7:33.   The moon, 3 days past first quarter, will set at 3:53 tomorrow morning.

Lets look at the moon again 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 this ruined crater will appear as a hook out into night off the upper left edge of the moon.  Officially its 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 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.

Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

Bay of Rainbows and the crater Copernicus. Created using Virtual Moon Atlas.