Archive
08/24/2015 – Ephemeris – The Bay of Rainbows
Ephemeris for Monday, August 24th. The Sun rises at 6:55. It’ll be up for 13 hours and 38 minutes, setting at 8:34. The Moon, 2 days past first quarter, will set at 2:17 tomorrow morning.
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
The Moon at 10 p.m. August 24, 2015 showing the location of Sinus Iridium. Created using Virtual Moon Atlas.
The moon at 10 p.m. August 24, 2015 with Sinus Iridium extending into the lunar night. Created using Virtual Moon Atlas.
This is for 2 hr UT August 25, 2015.
03/11/2014 – Ephemeris – Observing the moon tonight: Bay of Rainbows and more
Ephemeris for Tuesday, March 11th. The sun will rise at 8:02. It’ll be up for 11 hours and 41 minutes, setting at 7:43. The moon, 4 days past first quarter, will set at 5:39 tomorrow morning.
The moon tonight is a pretty fat gibbous shape, with the sunrise line or terminator revealing the Bay of Rainbows, Sinus Iridium, that large half crater at the moon’s upper left edge, and the edge of the Sea of Showers, Mare Imbrium. In the figure of the man in the moon Imbrium is his big eye, kind of like the cartoon “Bill the Cat”. To the right of it, looking like a hole in a mountain chain, is Plato, whose dark floor is unmistakable even at full moon, when shadows are absent. The crater Copernicus is now beginning to be washed out as the morning shadows shrink. To the left of Copernicus, just catching the sun’s rays on the terminator, is the smaller crater Kepler. When the moon is full Kepler will show a fine ray system.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon at 10 p.m. on March 11, 2014. Created using Virtual Moon Atlas.
Note for those not in the Eastern Daylight time zone. 10 p.m. is 2 hours March 12, 2014. If viewing before that time the terminator will be shifted to the right. After the terminator will be shifted to the left.
06/18/2013 – Ephemeris – The moon’s most striking feature, the Jura Mountains and the Bay of Rainbows
Ephemeris for Tuesday, June 18th. Today the sun will be up for 15 hours and 33 minutes, setting at 9:30. The moon, 2 days past first quarter, will set at 2:48 tomorrow morning. Tomorrow the sun will rise at 5:56.
On the moon tonight the gibbous phase and the terminator on the left side of the moon is revealing a large semi circular 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. The bay is Sinus Iridium, or Bay of Rainbows. It is easily visible in binoculars this evening when the sunrise line is crossing the bay. The Jura Mountains will appear as a hook at 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. Though the bay is the same gray as the rest of the moon, at least its name is colorful.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Bay of Rainbows (Sinus Iridium) within the Jura Mountains on the moon. Created using Virtual Moon Atlas.
09/25/2012 – Ephemeris – Sinus Iridium greets the sun
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.
05/12/11 – Ephemeris – Lunar telescopic wonders: Bay of Rainbows and the crater Copernicus
Thursday, May 12th. Today the sun will be up for 14 hours and 41 minutes, setting at 8:59. The moon, 2 days past first quarter, will set at 3:40 tomorrow morning. Tomorrow the sun will rise at 6:17.
Tonight the moon will again show a hook out into the darkness at the upper left edge of the moon for observers using binoculars or a telescope. That’s the Jura mountains cupping the Bay of Rainbows, a rather gray lava expanse on the edge of the Sea of Showers. At the other edge of the that sea is the great crater Copernicus, center left on the moon. Its halo of rays will show up better when the moon is full, but now the crater itself can be appreciated. In a telescope its is quite a sight. It has a complex triple central peak, and terraced walls. The small asteroid that hit it less than a billion years ago, struck the moon, gouging out the 56 mile diameter crater we see today. Rebound created the central peaks.
* 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.
I have more on Sinus Iridium and the Jura Mountains back in March.
Bob Moler's Ephemeris Blog 