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Posts Tagged ‘Far side’

Ephemeris: 04/17/2026 – The Moon’s Far Side isn’t dark!

April 17, 2026 Comments off

This is Bob Moler with Ephemeris for Friday, April 17th. Today the Sun will be up for 13 hours and 35 minutes, setting at 8:30, and it will rise tomorrow at 6:53. The Moon is new today, and won’t be visible.

When I hear discussions about the Artemis 2 missions, some people who ought to know better still refer to the far side of the moon as the dark side. Officially we have the two faces of the moon: the near side and the far side. I’ll even accept front side and back side. Until 1959 no one had ever seen the far side of the moon so it was dark, in the sense that we could not see it. Not dark because of the lack of light. I’ve been thinking about it. The far side sees more light from the sun, so maybe we should call it the bright side. It certainly has fewer maria or seas, those dark patches that we see on the near side of the Moon. There’s only one on the far side, it’s called the Moscow Sea since the Russian spotted first. Mare Orientale, subject of much study by the Artemis 2 crew, straddles the near side-far side line. It’s closer to the sun when it’s fully illuminated than the near side by about half a million miles, and it doesn’t suffer solar eclipses to darken it like the near side, being already in night, like it always is, at full moon.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Photograph of the crescent Earth setting behind the limb of the Moon by the Artemis 2 crew.
The far side may seem to be the dark side in this photograph of earthset by the Artemis 2 crew. It is as bright as the brightest parts of the near side. These are the crater filled highlands, so it is the exact same brightness as the highlands on the near side. And indeed in traveling to the Moon, when it was seen half near side and half far side, there was no difference in the brightness of the highlands between the two. So the moon is really dark gray in brightness, on average. It reflects something like 12% of the sunlight it receives, while the earth is more than twice that reflectance. Astronomers call that quantity albedo. So the Moon has an albedo of 12% while the Earth has an albedo of something like 29% on average. So the reason the full moon is so bright at night is due to lack of competition from something that’s actually much whiter. Credit: NASA/ESA/CSA -The Artemis 2 crew.
Categories: Astronomical fact, The Moon Tags: ,

Ephemeris: 04/14/2026 – My virtual flight with the Artemis II crew

April 14, 2026 Comments off

This is Ephemeris for Tuesday, April 14th. Today the Sun will be up for 13 hours and 26 minutes, setting at 8:26, and it will rise tomorrow at 6:58. The Moon, 3 days before new, will rise at 5:55 tomorrow morning.

I hadn’t enjoyable time last week Monday afternoon listening to Artemis 2 astronauts talking with the science team on Earth about what they were seeing Moon’s far side. I have the program called Virtual Moon Atlas which allows one to see the entire Moon with the phase and shadows. And I was able to rotate it and get the phase right so it appeared pretty much as it did to the astronauts. So I was able to follow along with their discussions of the far side features that they were seeing and photographing. I could zoom in to craters and features they were talking about, but nowhere near the detail they were seeing. So I consider it to be a really great time of, in essence, flying along with the astronauts.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EST, UT – 5 hours) unless stated otherwise. Times will be different for other locations.

Addendum

A view of the Moon from the camera attached to the solar panel of the European Service Module of the Orion spacecraft looking at the moon and crossing over the sunrise terminator on the far side.
This is a view of the Moon from the camera attached to the solar panel of the European Service Module of the Orion spacecraft looking at the moon and crossing over the sunrise terminator on the far side. The resolution of the image in on YouTube was about half the resolution of this image. Obviously the photographs that were taken would not be downloaded in real time as the lower resolution version of this image was. Credit: NASA European Space Agency.
A view from the Virtual Moon Atlas (VMA) from the approximate viewpoint of the Orion spacecraft at the time of the image above, with increased contrast and rotated. Being closer to the moon than this image depicts the edge or limb of the moon or horizon is much closer than is shown here so Oceanus Procellarum is over their horizon. They mentioned the crater Vavilov a lot, but VMA requires exact spelling to point it out. Clicking on a crater will display its name. Vavilov happens to be a double crater, and eventually I clicked on it, and got its name… Russian, of course.

Categories: Adventures, Artemis Program, Ephemeris Program, The Moon Tags: ,

Ephemeris: 04/07/2026 – The Artemis II crew made amazing observations of the Moon’s Far Side

April 7, 2026 3 comments

This post was made late due to some WordPress posting issues last night.

This is Ephemeris for Tuesday, April 7th. Today the Sun will be up for 13 hours and 5 minutes, setting at 8:18, and it will rise tomorrow at 7:10. The Moon, 3 days before last quarter, will rise at 2:33 tomorrow morning.

Yesterday evening the Artemis 2 crew flew over the far side of the moon. The moon to us has a waning gibbous phase. The far side is actually a waxing crescent, so most of the far side was in night. They might have gotten a good look at Mare Orientale, which is right on the edge of the moon that we see from Earth. It is a double-walled sea that looks like a bulls eye. Now they’re on their way back to the earth and will splash down in the Pacific Ocean later this week. Unlike Apollo 8 which orbited the moon, they will not be flying over any proposed landing sites. They flew over the moon’s equator while Artemis 4 will attempt to land near the moon’s South Pole. Besides, the Lunar Reconnaissance Orbiter has surveyed it much better than they could have.

The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EST, UT – 5 hours) unless stated otherwise. Times will be different for other locations.

Addendum

Mare Orientale
Mare Orientale by the LRO. Credit: NASA / GSFC / Arizona State Univ. / Lunar Reconnaissance Orbiter.

The script for the program seen above was written and recorded Sunday night April 5th before Artemis 2’s lunar flyby. This comment is made after the flyby on the late afternoon of April 6th. I speculated about Mare Orientale being something I wanted to have them investigate. And they did spend a great deal of time observing it, so we should expect some very nice photographs of it when they’re sent back. The image above is from the Lunar Reconnaissance Orbiter taken several years ago, at least. I find it a really cool feature.

Categories: Artemis Program, Ephemeris Program, Space exploration, The Moon Tags: , ,

Ephemeris: 04/11/2024 – What is the far side of the Moon good for?

April 11, 2024 Comments off

This is Ephemeris for Thursday, April 11th. Today the Sun will be up for 13 hours and 19 minutes, setting at 8:23, and it will rise tomorrow at 7:02. The Moon, 3 days past new, will set at 12:40 tomorrow morning.

The Last Monday when we were having an eclipse of the Sun, the far side of the Moon was fully illuminated. So it can’t possibly be the dark side of the Moon, not permanently. The dark side of the Moon is the night side and Monday that was the side facing the Earth. But what’s the far side of the Moon good for? The Chinese seem to be very interested in it. They have a lander and a rover on the far side, and they’re going to go back and grab a sample from the far side and bring it back to the Earth. The far side of the Moon is one place in the whole solar system in which the cacophony of radio signals from the Earth cannot be heard so it’s a great place to set up a radio telescope. The craters on the far side of the moon might be used to place a dish antenna.

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

Near Side and Far Side of the Moon Compared
The near side and the far side of the Moon compared. Notice how different they are with the near side dominated by the dark lava seas and the far side by the less dark highlands. The one sea on the far side is at 10 o’clock is the Sea of Moscow, and the other dark spot to the lower lower left about 8 o’clock is the crater Tsiolkovsky named after famous Russian scientist Konstantin Tsiolkovsky (1857-1935)a pioneer in aeronautic, and rocket theory. The Soviets were first to send a probe (Luna 3) around the far side of the Moon in 1959, and got to name the major features they photographed.
Lunar Crater Radio Telescope
A concept for a lunar crater radio telescope . The telescope is in the style of Arecibo, the now collapsed radio telescope in Puerto Rico . Aiming would be accomplished by shifting the suspended receiver. Credit: NASA, Saptarshi Bandyopadhyay.
Categories: The Moon Tags: ,

Ephemeris: 01/23/2024- The “dark” side of the Moon is its brightest side

January 23, 2024 Comments off

This is Ephemeris for Tuesday, January 23rd. Today the Sun will be up for 9 hours and 27 minutes, setting at 5:38, and it will rise tomorrow at 8:10. The Moon, 2 days before full, will set at 8 o’clock tomorrow morning.

In a couple of days the far side of the Moon will become the dark side for real. It’ll be night when the near side of the moon becomes fully illuminated, the far side will be a night. The far side of the moon actually gets more sunlight than the near side of the moon because it does not suffer solar eclipses. The lunar solar eclipse occurs when we see a lunar eclipse. The Sun is blocked from shining on the Moon. The totality of a lunar solar eclipse lasts much longer than a few minutes that we get when the Moon totally blocks the Sun, the length of totality for the Moon’s solar eclipse can last several hours. The far side of the moon does not see eclipses, and when fully illuminated at what we call new moon it is a quarter of a million miles closer to the Sun than Earth.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.

Addendum

The near side and the far side of the Moon compared
The near side and the far side of the Moon compared. On the far side the only really dark areas are the Moscow Sea at the 10 o’clock position and the crater Tsiolkovsky at the 8 o’clock position. The large semi dark area at the 5 o’clock position is the Aitken basin which would probably be a lot darker if the impact that created it had occurred on the near side of the Moon. Click or tap on the image to enlarge it. Credit NASA, Clementine spacecraft.
Categories: Ephemeris Program, The Moon Tags: , ,

03/11/2019 – Ephemeris – The Moon: Dark side, far side, which is it?

March 11, 2019 Comments off

Ephemeris for Monday, March 11th. Today the Sun will be up for 11 hours and 40 minutes, setting at 7:43, and it will rise tomorrow at 8:01. The Moon, 3 days before first quarter, will set at 12:54 tomorrow morning.

Tonight the Moon is at its crescent phase, meaning it is slightly closer to the Sun than the Earth is. Most of the Moon we see is in night. Some earth shine may be seen on its night side due to the big nearly full Earth shining on it. I get ticked sometimes when someone who knows better, especially in the media, mentions the dark side of the Moon when they should use the term far side, the part of the Moon that permanently faces away from the Earth. When the Chinese Chang’e 4 spacecraft landed on the far side of the Moon recently many headlines proclaimed that it landed on the dark side of the Moon. The Moon has a night side, as does the Earth, but that changes as the Moon rotates in the sunlight.  And the Moon does rotate.  It happens to be in sync with its revolution about the Earth.

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

Addendum

Crescent Moon

The crescent Moon tonight at 9 p.m. EDT, March 11, 2019. Created using Stellarium.

Moon ball

Demonstration of the Moon’s crescent phase with the Styrofoam moon ball we use for Project Astro held up to a light off frame to the right. The night side of the ball is illuminated a bit by the translucency of the ball, and the reflection off my hand. Note the roughness of the ball is visible only at the terminator.

The crescent Moon and its relation the Earth

The Earth and Moon if seen as a crescent, near side, far side, sunlit side and earth shine. Credit: me.

Categories: Concepts, Ephemeris Program, Phases, The Moon Tags: , , ,