Archive
Ephemeris: 05/18/2026 – Earth shines on the Moon
This is Bob Moler with Ephemeris for Monday, May 18th. Today the Sun will be up for 14 hours and 56 minutes, setting at 9:07, and it will rise tomorrow at 6:10. The Moon, 2 days past new, will set at 12:07 tomorrow morning.
The Moon tonight will appear as a thin sliver, with Venus below and left of it. However, if as you look at the Moon closely tonight you may have the funny feeling that the whole moon is actually visible, you would be right. It’s easily confirmed with a pair of binoculars or a small telescope. What is illuminating the dark part of the Moon is earthshine. The Earth is big and bright in the Moon’s sky, as a fat waning gibbous orb from its vantage point. From the Moon the Earth has the opposite phase that we see of the Moon from the Earth. The effect used to be called by the term “Old moon in the new moon’s arms”. The effect was first explained by Leonardo da Vinci some 500 years ago. The effect will disappear in a few days as the Moon gets brighter and the Earth less so in the Moon’s sky. Earthshine will appear again when the Moon appears as a waning crescent in the morning. But not many of us are up to see it at that hour.
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
Ephemeris: 04/27/2026 – Mare Orientale made a splash!
This is Ephemeris for Monday, April 27th. Today the Sun will be up for 14 hours and 4 minutes, setting at 8:42, and it will rise tomorrow at 6:37. The Moon, halfway from first quarter to full, will set at 5:06 tomorrow morning.
One of the pictures that the astronauts of Artemis 2 took of the far side of the moon was one that revealed chains of craters which appear to be emanating from the Sea on the edge of what we can see on the moon from the Earth, called Mare Orientale or the Eastern Sea. It was created by the impact of an asteroid onto the Moon’s surface, maybe 4 billion years ago, kicking out debris in all directions. Apparently the ejecta thrown out created chains of craters that appear to trace back to Orientale. They are most easily seen to the north and west of Orientale towards the terminator, the sunrise line, where the shadows are deeper. There’s probably chains of craters going in other directions, but they have no shadows.
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
Ephemeris: 04/16/2026 – The greatest distance humans have traveled from the Earth
This is Ephemeris for Thursday, April 16th. Today the Sun will be up for 13 hours and 32 minutes, setting at 8:29, and it will rise tomorrow at 6:54. The Moon, 1 day before new, will rise at 6:38 tomorrow morning.
On their trip around the moon the Artemis 2 crew set a new record for distance from the earth of 252,760 miles (406,778 kilometers) which beat by 4,105 miles (6,607 kilometers) the record of Apollo 13 of 248,655 miles (400,171 kilometers). This was helped a great deal by the fact that the moon reached apogee, its farthest distance from the Earth, a few hours after the Artemis 2 capsule, Integrity, passed by. So I think the record is going to hold up for a while. So the only way to get further away from the earth is to head out to Mars, or the Chinese make a farther flyby of the Moon. The Artemis 2 mission was to see if the capsule can sustain human life comfortably during an extended mission. It seemed proved it’s worth. The videos that came back seem to be reasonably roomy, much more so than the Apollo capsule.
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
Ephemeris: 04/14/2026 – My virtual flight with the Artemis II crew
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
Ephemeris: 04/07/2026 – The Artemis II crew made amazing observations of the Moon’s Far Side
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
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.
Ephemeris: 02/05/2026 – Artemis 3 isn’t going to the Moon
This is Ephemeris for Thursday, March 5th. Today the Sun will be up for 11 hours and 22 minutes, setting at 6:36, and it will rise tomorrow at 7:11. The Moon, 2 days past full, will rise at 9:22 this evening.
Late last week NASA announced that the Artemis 3 mission was not going to land on the Moon. It wasn’t even going to the Moon. It would be a low earth orbit test of docking and operations of the Human Landing System or lunar landers, either the SpaceX Starship Lander or Blue Origin’s Blue Moon Lander. This reminds me of the Apollo 9 mission which came after the spectacular Apollo 8 mission which orbited the Moon. Apollo 9 was a checkout of the Lunar Lander in low earth orbit. Several Months later, Apollo 10 flew to the Moon to a checkout of the Lunar Lander in lunar orbit. They couldn’t land, but it was a test of the operations in preparation for Apollo 11 which successfully landed on the 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; EST, UT – 5 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 02/10/2026 – Artemis 2 is delayed until at least March
This is Ephemeris for Tuesday, February 10th. Today the Sun will be up for 10 hours and 14 minutes, setting at 6:04, and it will rise tomorrow at 7:48. The Moon, 1 day past last quarter, will rise at 4:03 tomorrow morning.
The next attempt to launch Artemis 2 and its crew around the moon will be in March. During the wet dress rehearsal, which involves filling the tanks of the huge core stage of the rocket with liquid hydrogen and oxygen, and counting down almost to the point of ignition. They discovered a greater than expected leak with the hydrogen quick disconnect fitting at the base of the core stage. They can’t test for hydrogen leaks while the spacecraft is sitting in the vertical assembly building because as cavernous as it is, it’s still a closed space and hydrogen is a notoriously leaky substance, being the smallest molecule. A little leakage is to be expected, but what they found was over the limit.
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
Ephemeris: 01/29/2026 – After Artemis 2 comes Artemis 3 and the landing
This is Ephemeris for Thursday, January 29th. Today the Sun will be up for 9 hours and 42 minutes, setting at 5:47, and it will rise tomorrow at 8:04. The Moon, 3 days before full, will set at 6:44 tomorrow morning.
If Artemis 2 is successful in the late winter and early spring of this year, the next mission will be Artemis 3, a mission to land near the South Pole of the Moon. In order for that to happen a lunar Lander will have to be ready and tested. The Starship HLS or human landing system is currently being built by SpaceX. It’s delivery to the Moon, via Superheavy, Starship’s big booster, will require multiple launches and refueling in orbit, which has yet to be tested. There has been some question as to how many refueling trips will be necessary. NASA and SpaceX seem to differ. However, an uncrewed successful landing will have to be made to prove out the system before the Artemis 3 landing will be attempted.
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
Ephemeris: 01/27/2026 – Orion’s heat shield problem
This is Ephemeris for Tuesday, January 27th. Today the Sun will be up for 9 hours and 37 minutes, setting at 5:44, and it will rise tomorrow at 8:06. The Moon, 2 days past first quarter, will set at 4:29 tomorrow morning.
One of the problems that was detected with the reentry of the Artemis 1 mission back in November 2022* was the degradation of the heat shield of the Orion capsule. Chunks of the heat shield actually were breaking off. The technique they use for reentry called the skip reentry was thought to be the culprit. So while they are attempting to redesign the heat shield, Artemis 2 will be using the same type heat shield, but they will not do a skip reentry and come in without a skip off the atmosphere. The reason for using a skip reentry is to lessen the amount of Gs that are pulled by the capsule coming in at 7 miles per second by prolonging the entry and increasing the downrange travel of the capsule. Skip reentry is a proven technique, the Russians have been doing it for decades.
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.
* For the broadcast, I misremembered the date as December 2024. That’s what happens when you’re old.
Addendum
Ephemeris: 01/26/2026 – Artemis, not just flags and footprints
This is Ephemeris for Monday, January 26th. Today the Sun will be up for 9 hours and 35 minutes, setting at 5:43, and it will rise tomorrow at 8:07. The Moon, 1 day past first quarter, will set at 3:10 tomorrow morning.
The current space race or I might say more properly, Moon race, is more than it was in the 1960s this race is not simply what is called a flag and footprints race get there first and go home. We already did that 57 years ago. But to set up permanent settlements on the moon to explore and extract the Moon’s resources like water. Water is not for export. Whatever water we find on the Moon would still be fairly scarce and probably rationed. There’s also an unknown amount of helium 3, which is a useful fuel for fusion reactors. Something we don’t have on the Earth, but would be the Holy Grail for clean energy production. We don’t know the Moon’s mineral potential, but whatever we find won’t have to be hauled up a quarter of a million miles from the Earth.
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
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