Archive

Posts Tagged ‘Straight Wall’

10/03/2022 – Ephemeris – There’s something on the Moon that’s straight and not circular

October 3, 2022 Comments off

This is Ephemeris for Monday, October 3rd. Today the Sun will be up for 11 hours and 36 minutes, setting at 7:19, and it will rise tomorrow at 7:44. The Moon, 1 day past first quarter, will set at 12:55 tomorrow morning.

On this program, I try to talk about celestial objects one can see or find with the naked eye. Once found, I do talk about what they would look like in binoculars or small telescope. For those wanting more information, consult my blog bobmoler.wordpress.com where my scripts are posted with more information, illustrations and charts. The thing I’m talking about today is a feature on the Moon that’s visible only two nights a month. The day after first quarter, and the day after last quarter. It’s the straightest thing on the Moon, called the Straight Wall, that’s 67 miles (110 km) long and 900 feet (300 m) high. It is close to the terminator, the Moon’s sunrise line, about halfway from the center of the Moon to the south edge. It’s the thinnest dark line you can imagine.

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 Straight Wall or, officially in Latin, Rupes Recta, is a rectilinear fault. It isn’t really a wall, but a 7 degree slope. Once the Sun rises past seven degrees in that location of the Moon, it disappears. Near local sunset, a day after last quarter, the low sun in its sky shines more on it than the flat ground, so it shows up bright. Click on the image to enlarge it. The information and images were created from Virtual Moon Atlas, which is free software for MS Windows. I have a link to it on this page.

06/07/2022 – Ephemeris – The Moon’s Straight Wall

June 7, 2022 Comments off

This is Ephemeris for Tuesday, June 7th. Today the Sun will be up for 15 hours and 28 minutes, setting at 9:25, and it will rise tomorrow at 5:57. The Moon, at first quarter today, will set at 2:49 tomorrow morning.

Around the first quarter Moon there is, among all the circular formations on the Moon like craters, something that’s straight. Its name is Rupes Recta, better known as the Straight Wall. Tonight it’s a dark line seen near and parallel to the terminator, the sunrise line on the Moon, about a third of the way down from the center of the Moon’s disc to the edge. It looks like a cliff that’s 900 feet (300 meters) high and 67 miles (110 kilometers) long. It’s not. It is apparently a rectilinear fault, and its slope is only 7 degrees. It will disappear as the sun rises higher and illuminates the slope. It can be spotted in a small telescope, though it requires something generally larger and more powerful than a pair of binoculars. Near last quarter, the Straight Wall appears as a bright line.

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

Moon's Straight Wall locator

Moon’s Straight Wall locator, though it may not be visible at this magnification. Created using Virtual Moon Atlas.

Enlargement of the area of the Straight Wall

Enlargement of the area of the Straight Wall with labels blinking on and off. Created using Virtual Moon Atlas, Libreoffice, and GIMP.

Enlargement of the area of the Straight Wall near last quarter. Created using Virtual Moon Atlas.

11/19/2015 – Ephemeris – The no longer quite first quarter Moon tonight

November 19, 2015 Comments off

Ephemeris for Thursday, November 19th.  The Sun will rise at 7:44.  It’ll be up for 9 hours and 26 minutes, setting at 5:11.   The Moon, at first quarter today, will set at 1:06 tomorrow morning.

The Moon actually was at first quarter at 1:27 (6:47 UT) this morning.  By this evening, when it’s out the terminator, the sunrise line, on the Moon will be curved giving the it a definite gibbous appearance.  The upside down rabbit image in the Moon’s dark seas on the illuminated right half can be seen.    In a telescope or even powerful binoculars at 9 p.m. the Terminator cuts the southern crater Tycho in half.  The large crater Clavius south of it is just catching the morning Sun.  To the north the sunrise line cuts the large Mare Imbrium or Sea of Showers in half. In the mountains on the north shore of Imbrium the large walled plain, really a crater, Plato can be seen.  Pan near the terminator in the south and the Straight Wall might be spotted as a long shadow.

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

Addendum

Moon

The Moon at 9 p.m. EST November 19, 2015. (2 hr UT November 20) Created using Virtual Moon Atlas.

Closeup of the Straight Wall

Closeup chart of the Straight Wall.