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Ephemeris: 07/27/2023 – See the Moon’s Bay of Rainbows at sunrise
This is Bob Moler with Ephemeris for Thursday, July 27th. Today the Sun will be up for 14 hours and 51 minutes, setting at 9:14, and it will rise tomorrow at 6:24. The Moon, 2 days past first quarter, will set at 1:38 tomorrow morning.
The moon tonight is a waxing gibbous phase, so it’s more than half illuminated by the Sun. The line between light and dark on the left side of the Moon is called the terminator, which before full is the sunrise line. It is where we can see the greatest detail because the Sun is low in the Moon’s sky there, and creates the longest shadows. Compare it to the right side of the Moon which is seen at nearly solar noon where no shadows are seen, so it has a very bland appearance. One of the cool features of the gibbous moon tonight is Sinus Iridium, the Bay of Rainbows, which is on the upper left part of the terminator. Part of the mountain range that partially rings it is seen in sunlight, while that floor of the bay is still in shadow.
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
05/29/2023 – Ephemeris – Sinus Iridium, a hook into night
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
06/09/2022 – Ephemeris – Looking at the gibbous Moon tonight
This is Bob Moler with Ephemeris for Thursday, June 9th. Today the Sun will be up for 15 hours and 29 minutes, setting at 9:27, and it will rise tomorrow at 5:57. The Moon, 2 days past first quarter, will set at 3:29 tomorrow morning.
By tonight, the gibbous moon will be quite bright. At the moon’s left edge, just coming into sunlight, will be what looks like a large half crater at the edge of the lunar sea called Mare Imbrium, the Sea of Showers. That feature is Sinus Iridium, or Bay of Rainbows. The arc of its mountainous edge is rainbow shaped, but it is as colorless as the rest of the Moon. The crater Copernicus sports few shadows and appears mostly as a bright spot surrounded by its ray system of ejecta craters that appear bright when the sun is high in their sky. At the south end of the Moon are the lunar highlands, bright, rugged and covered by large, mostly very old craters. Largest of these craters is Clavius, named for Christophorus Clavius who, working for Pope Gregory XIII, devised the Gregorian Calendar we use today.
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
Binocular Moon as it might appear tonight, June 9, 2022. Below, we’ll look closer to the terminator area of the Moon. Created using Virtual Moon Atlas.
Northern gibbous Moon terminator area with labels for some prominent features. Created using Virtual Moon Atlas, LibreOffice and GIMP.
Southern gibbous Moon terminator area with labels for some prominent features. Created using Virtual Moon Atlas, LibreOffice and GIMP.
Translations
Mare Frigoris – Sea of Cold
Mare Imbrium – Sea of Showers
Mare Nubium – Sea of Clouds
Montes Alpes – Alps Mountains
Montes Appinenninus – Apennines Mountains
Sinus Iridium – Bay of Rainbows
02/11/2022 – Ephemeris – The Sun Rises on the Moon’s Bay of Rainbows
This is Ephemeris for Friday, February 11th. Today the Sun will be up for 10 hours and 16 minutes, setting at 6:05, and it will rise tomorrow at 7:47. The Moon, 3 days past first quarter, will set at 5:34 tomorrow morning.
On the moon tonight, the gibbous phase and the terminator on the left side of the moon is revealing a large semicircular mountain range called the Jura Mountains that encloses a flat lava plain that looks like a bay in the margin of the Sea of Showers or Mare Imbrium. It is easily visible in binoculars this evening, when the sunrise line is crossing the bay. The Jura Mountains will appear as a hook out of the upper left edge of the moon. That’s about the coolest sight that’s visible on the moon that can be seen with binoculars. It’s especially striking if seen in a small telescope.
Also, related to the Moon: The Artemis-1 uncrewed mission to orbit the Moon has been pushed off at least one month or more, to this April or even May.
Addendum
Sunrise at Sinus Iridium, full Moon disc with annotations. Click on the image to enlarge it. Moon image created using Stellarium.
Sinus Iridium at sunrise. Photo by “Seb2003” on http://forums.futura-sciences.com/materiel-astronomique-photos-damateurs/5809-images-de-lune.html.
03/23/2021 – Ephemeris – The Moon tonight: Bay of Rainbows
This is Bob Moler with Ephemeris for Tuesday, March 23rd. Today the Sun will be up for 12 hours and 19 minutes, setting at 7:59, and it will rise tomorrow at 7:37. The Moon, 2 days past first quarter, will set at 5:50 tomorrow morning.
A look at the Moon tonight will reveal that the sunrise line, or terminator has almost completely revealed the large Sea of Showers or Mare Imbrium to the upper left of the center of the gibbous disk. At the extreme upper left nearly completely in sunlight a very popular feature, the Bay of Rainbows or Sinus Iridium. It’s a colorful name for something that’s as gray as the rest of the Moon. It looks like a bay off of Imbrium, and has an arch like a rainbow. Its arch is the Jura Mountains, which jut into Mare Imbrium at Cape Heraclide, just catching sunlight, and Cape Laplace farther into morning. What’s cool is catching it as the sunlight is hitting the mountains while the convex floor, following the Moon’s curvature is only partially illuminated.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon a little before how it will appear tonight highlighting Sinus Iridium. By tonight the floor of Sinus Iridium should be pretty much sunlit, and the Jura mountains completely lit. Created using Virtual Moon Atlas.
Sinus Iridium at sunrise. Photo by “Seb2003” on http://forums.futura-sciences.com/materiel-astronomique-photos-damateurs/5809-images-de-lune.html.
11/07/2019 – Ephemeris – The gibbous Moon tonight
Ephemeris for Thursday, November 7th. Today the Sun will be up for 9 hours and 55 minutes, setting at 5:23, and it will rise tomorrow at 7:30. The Moon, 3 days past first quarter, will set at 3:13 tomorrow morning.
Every night when we look at the Moon the sunrise terminator has moved farther west on the Moon which is to our east uncovering more landscape. The Moon rotates once in about 29 ½ days in relation with the Sun. This is the same time it orbits the Earth from new Moon to the next. We call that a lunation or lunar month. Near the upper left corner of the Moon is what looks like a half crater. It’s called Sinus Iridium, the Bay of Rainbows. It’s at the edge of Mare Imbrium or Sea of Showers. To the south cut by the terminator is Oceanus Procellarum, the flat Ocean of Storms. South of that is the small Mare Humorum, the Sea of Vapors. South of all that is the odd shaped crater Schiller.
10-11-2016 has images
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The gibbous Moon tonight at 8 p.m., November 7, 2019. Click on the image to enlarge. Created using Virtual Moon Atlas.
Sinus Iridium photographed by the Lunar Reconnaissance Orbiter as texture mapped on the globe of the Virtual Moon Atlas.
Clavius as photographed by one of the Lunar Orbiter spacecraft in the 1960s From Digital Lunar Orbital Photographic Atlas. This is photographed from overhead. On tonight’s moon it’s near the bottom or south end and is foreshortened.Credit Jeff Gillis, Lunar and Planetary Institute.
01/26/2018 – Ephemeris – The Moon tonight: The Bay of Rainbows
Ephemeris for Friday, January 26th. The Sun will rise at 8:08. It’ll be up for 9 hours and 34 minutes, setting at 5:43. The Moon, 2 days past first quarter, will set at 3:59 tomorrow morning.
A look at the Moon tonight will reveal that the sunrise line, or terminator has almost completely revealed the large sea of Showers or Mare Imbrium to the upper left of center of the gibbous disk. At the extreme upper left straddling the terminator is one of my favorite features, the Bay of Rainbows or Sinus Iridium. It’s a colorful name for something that’s as gray as the rest of the Moon. It looks like a bay off of Imbrium, and has an arch like a rainbow. It’s arch is the Jura Mountains, which jut into Mare Imbrium at Cape Heraclide, just catching sunlight, and Cape Laplace farther into morning. What’s cool is catching it as the sunlight is hitting the mountains while the convex floor, following the Moon’s curvature is only partially illuminated.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon at 8 p.m. January 26, 2018 highlighting Sinus Iridium. Created using Virtual Moon Atlas.
Sinus Iridium photographed by the Lunar Reconnaissance Orbiter as texture mapped on the globe of the Virtual Moon Atlas.
Sinus Iridium at sunrise. Photo by “Seb2003” on http://forums.futura-sciences.com/materiel-astronomique-photos-damateurs/5809-images-de-lune.html.
10/11/2016 – Ephemeris – Looking at the Moon tonight
Ephemeris for Tuesday, October 11th. The Sun will rise at 7:53. It’ll be up for 11 hours and 10 minutes, setting at 7:04. The Moon, 2 days past first quarter, will set at 3:26 tomorrow morning.
We looked at the Moon in the last program, now 24 hours later the sunrise terminator has moved farther west, our east uncovering more landscape. The Moon rotates once in about 29 ½ days in relation with the Sun. This is the same time it orbits the Earth from new Moon to the next. We call that a lunation or lunar month. Near the upper left corner of the Moon is what looks like a half crater. It’s called Sinus Iridium, the Bay of Rainbows. It’s at the edge of Mare Imbrium or Sea of Showers. To the south cut by the terminator is Oceanus Procellarum, the flat Ocean of Storms. South of that is the small Mare Humorum, the Sea of Vapors. Between then is a distinctive crater Gassendi. South of all that is the odd shaped crater Schiller.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon at 9 p.m. October 11, 2016. Created using Virtual Moon Atlas.
Sinus Iridium photographed by the Lunar Reconnaissance Orbiter as texture mapped on the globe of the Virtual Moon Atlas.
The crater Gassendi from Apollo 16 – NASA
The craters Schickard and Schiller as seen from above from the Lunar Reconnaissance Orbiter. The Sun will start to rise on Schickard tomorrow night. Credit NASA from Virtual Moon Atlas.
05/16/2016 – Ephemeris – The Sun rises on the Bay of Rainbows
Ephemeris for Monday, May 16th. Today the Sun will be up for 14 hours and 53 minutes, setting at 9:06. The Moon, 3 days past first quarter, will set at 4:23 tomorrow morning. Tomorrow the Sun will rise at 6:11.
One of my favorite lunar formations is creeping into sunlight on the Moon this evening. Look to the upper left edge of the moon tonight. The large sea or dark area of the Moon, the Man in the Moon’s right eye as he’s looking at us is Mare Imbrium, the Sea of Showers. At the top left edge of that sea is a large notch. And keeping with of seas these of the first telescopic astronomers its name is Sinus Iridium, or Bay of Rainbows, a colorful name for something as colorless as the rest of the Moon. The terminator which is the sunrise line will be cutting across that bay, illuminating the semicircular mountain ring that surrounds it before all of the floor is illuminated. It can be seen in binoculars or a small telescope.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Image showing the Moon tonight at 10 p.m., May 16, 2016 (2 hr, May 17, 2016 UT) with Sinus Iridium (Bay of Rainbows) just coming into sunlight. Created using the Virtual Moon Atlas.
10/22/2015 – Ephemeris – My favorite lunar feature
Ephemeris for Thursday, October 22nd. The Sun will rise at 8:07. It’ll be up for 10 hours and 39 minutes, setting at 6:46. The Moon, 2 days past first quarter, will set at 3:10 tomorrow morning.
The Moon tonight is revealing my favorite feature, Sinus Iridium or Bay of Rainbows. Unfortunately features on the Moon are not that colorful. The Bay of Rainbows is surrounded on three sides by a semicircular mountain range called the Jura Mountains which is actually a broken down crater wall. The Bay is a bay in Mare Imbrium, the Sea of Showers. It is the nomenclature of land forms on planets and moons that still have Latin names in astronomy. That and constellations. Of course the Bay of Rainbows and the Sea of Showers aren’t real bodies of water. These were the product of the imaginations of astronomers looking through their primitive telescopes, at a completely alien landscape.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon tonight with Sinus Iridium peeking out into the morning sunlight on the Moon, 9 p.m. October 2015. Created using Virtual Moon Atlas.
Sinus Iridium photographed by the Lunar Reconnaissance Orbiter as texture mapped on the globe of the Virtual Moon Atlas.
Bob Moler's Ephemeris Blog 