Archive
Ephemeris: 08/07/2025 – Does the Moon rotate?
This is Ephemeris for Thursday, August 7th. Today the Sun will be up for 14 hours and 23 minutes, setting at 9:00, and it will rise tomorrow at 6:37. The Moon, 2 days before full, will set at 5:26 tomorrow morning.
The moon exhibits the same face to the Earth throughout the month. That doesn’t mean the Moon doesn’t rotate. It means that the moon rotates in the same time it takes to orbit the Earth. This is called synchronous rotation. It is also known as tidal locking, caused by the difference in the gravitational attraction across the body of the Moon from the near side to the far side. The same thing happens with the Earth and is best seen by the ocean tides on the part of the Earth facing and away from the Moon. The reason the Earth is not tidally locked is that it is much more massive. But the Moon is slowing down the Earth’s rotation. But by doing that, it is moving further away, so it will never totally lock the Earth’s rotation with it.
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: 08/05/2025 – Why space faring nations are fixated on the Moon’s South Pole
This is Ephemeris for Tuesday, August 5th. Today the Sun will be up for 14 hours and 28 minutes, setting at 9:02, and it will rise tomorrow at 6:35. The Moon, halfway from first quarter to full, will set at 3:06 tomorrow morning.
After more than 50 years since the Apollo landings on the Moon, space faring nations are beginning to be interested in one particular place on the Moon for further exploration. That is the lunar South Pole. The reason is the discovery of something more valuable than gold. That there may be water hidden in permanently shadowed craters there. The moon’s North Pole is not as rugged, so there’s probably not as much water there. Water can exist on the Moon but only in its frozen form, ice in permanently shadowed craters. The Moon’s axial tilt is only about 1 1/2° compared to the Earth’s 23 1/2°. The water molecule is the second most abundant in the universe after diatomic hydrogen, but normally cannot exist this close to the Sun.
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: 07/07/2025 – Old and new explanations of the Moon’s appearance
This is Ephemeris for Monday, July 7th. Today the Sun will be up for 15 hours and 24 minutes, setting at 9:30, and it will rise tomorrow at 6:05. The Moon, 3 days before full, will set at 3:30 tomorrow morning.
The Moon’s changing appearance over the month may seem to be mysterious at first glance. Maybe because one may think that the objects in the sky are somehow different from the familiar objects we see around us on the Earth. In ancient times, especially the Greeks thought that everything in the heavens was perfect and spotless. They explained the definite markings we see as the man-in-the-moon as a reflection of the Earth by a spotless Moon. The Moon’s phases are simply light and shadow on a ball in the sunlight. Sometime, when the Moon appears in the daytime, take a small ball, like a golf ball and hold it up to the Moon, while the ball is also in sunlight, and the small ball will exhibit the same phase as the Moon.
See 10/12/18
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: 06/03/2025 – Looking at the Moon tonight
This is Bob Moler with Ephemeris for Tuesday, June 3rd. Today the Sun will be up for 15 hours and 23 minutes, setting at 9:23, and it will rise tomorrow at 5:58. The Moon, 1 day past first quarter, will set at 2:41 tomorrow morning.
For me, the best time to view the Moon with binoculars or a telescope is around first quarter and tonight’s Moon is just a day past first quarter. At this time we see the maximum amount of shadowing of the craters because the sunrise line which we call the terminator is cutting across, pretty much, the center of the Moon. Since the Moon is a pretty uniformly dark gray with light gray areas, shadows make all the difference in seeing detail. One thing to notice on tonight’s Moon is that the southern or bottom part of the Moon has a lot of craters and is bright gray. This is called the lunar highlands and is brighter than the darker areas to the north and on the western side of the Moon, which are covered by the maria or seas, plains of solidified lava flows.
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
Translations of some lunar feature names according to Virtual Moon Atlas
Lacus Mortis – Lake of Death
Lacus Somniorum – Lake of Dreams
Mare Crisium – Sea of Crises
Mare Fecunditatis – Sea of Fruitfulness
Mare Frigoris – Sea of Cold
Mare Imbrium – Sea of Showers
Mare Nectaris – Sea of Nectar
Mare Serenitatis – Sea of Serenity
Mare Tranquillitatis – Sea of Tranquility
Mare Vaporum – Sea of Vapors
Montes Alpes – Alps Mountains
Montes Apenninus – Apennines Mountains
Sinus Asperitatis – Bay of Roughness
Sinus Medii – Central Bay
Note: Mare is pronounced Mar-e, and Maria is pronounced Mar-e-a.
These features, for the most part, were named by Giovanni Battista Riccioli in 1651, when he produced the first accurate map of the Moon. Craters are named for persons, real or otherwise. Features like Seas, Lakes and Bays were given fanciful names. Labels are centered on their feature where possible.
Ephemeris: 04/03/2025 – Blue Ghost’s two week long cold night
This is Ephemeris for Thursday, April 3rd. Today the Sun will be up for 12 hours and 53 minutes, setting at 8:13, and it will rise tomorrow at 7:17. The Moon, 1 day before first quarter, will set at 3:23 tomorrow morning.
During the last lunar day the Blue Ghost Lander spend its time from little after sunrise until a little after sunset investigating the surface of the Moon at the lunar Sea of Crises or Mare Crisium. It wasn’t expected to survive the two-week-long night. It wasn’t expected to because it had no internal heating and at night the temperatures on the Moon can drop to down to minus 208° F, or a little bit more on the night side. During the day the temperature gets up to 250° which is pretty hot for some of the electronics. But what really kills a Lander is at night where they can’t recharge the batteries and the batteries drop in temperature to 200° below zero for two weeks. They generally do not survive.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Ephemeris: 03/10/2025 – Aristarchus, the brightest spot on the Moon, but not tonight
This is Ephemeris for Monday, March 10th. Today the Sun will be up for 11 hours and 39 minutes, setting at 7:42, and it will rise tomorrow at 8:01. The Moon, 4 days before full, will set at 7:11 tomorrow morning.
The moon tonight is bright. The sunrise line or terminator on the moon is crossing the large gray plain called Oceanus Procellarum, the largest of the moon’s seas. These seas were figments of the first telescopic observer’s imagination. They are really huge impact basins into which interior lava flowed. On the left edge of the Moon, just below center, this evening, at the terminator is a small shadow filled crater that might be visible in binoculars, but definitely telescopes. It’s called Aristarchus. It is a fairly new crater, probably less than a billion years old. As a rule the brighter the crater the newer it is. Aristarchus is the brightest spot on the Moon, when it is full. Visual astronomers have seen hazes and bright spots on rare occasions in and near Aristarchus.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Aristarchus tonight, March 10, 2025, on the terminator (left), and Friday night, the 14th, before the total lunar eclipse starts. The enlargements show the telescopic view. Created using Stellarium, LibreOffice Draw and GIMP. The Moon doesn’t actually appear larger on the 14th. Apparently my field of view changed while getting the 14th’s image.
Ephemeris: 03/06/2025 – The Moon at first quarter
This is Ephemeris for Thursday, March 6th. Today the Sun will be up for 11 hours and 26 minutes, setting at 6:37, and it will rise tomorrow at 7:09. The Moon, at first quarter today, will set at 3:31 tomorrow morning.
The Moon is indeed at first quarter today with the instant of being 90° from the Sun coming at 11:32 this morning. To me the first quarter moon is the best time to view because there are a lot of craters that are visible in deep shadow. The terminator, the sunrise line, on the Moon cuts the disk in half and a lot of craters can even be seen in binoculars. With a small telescope the jumble of craters provides a wonderful view of the destruction of the early bombardment of the Moon in its early days. The reason the Moon has all these craters and the Earth does not is the fact that the Earth has an active surface with volcanoes, plate tectonics, water and wind to erode and deform the surface. The Moon has really none of that.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 03/03/2025 – The Moon tonight
This is Bob Moler with Ephemeris for Monday, March 3rd. Today the Sun will be up for 11 hours and 17 minutes, setting at 6:33, and it will rise tomorrow at 7:14. The Moon, 3 days before first quarter, will set at 11:40 this evening.
Tonight the moon will be four days old. The age of the moon is the number of days since the new moon which ranges from 1 to 28 or 29 for the lunar month. I usually don’t use that, being more concerned with the phase of the Moon so at the top of the program I give the moon’s relation to its new, quarter, or full phase. Being in its waxing crescent phase right now, the only features to the naked eye on the Moon besides the crescent itself are the dark Sea of Crises, Mare Crisium, target of Firefly Aerospace’s Blue Ghost Lander, and the larger Sea of Fruitfulness, Mare Fecunditatis. The Moon rotates about 1/28th the speed of the Earth, and it’s also smaller, about a quarter of the Earth’s diameter. So one would have to use a supersonic jet to fly around the Earth to keep up with the rotation, but on the Moon one could do that with the Apollo moon rover.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 02/10/2025 – How old are the features on the Moon?
This is Ephemeris for Monday, 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, 2 days before full, will set at 7:42 tomorrow morning.
In dating Moon rocks scientists get a range of dates from 4.6 to 3.3 billion years. An age of a rock is determined by the decay of a radioactive element one of which is uranium 238 decaying to lead 206. So the ratios of these two elements gives a date when a rock was last solidified. This clock is reset when a rock was last melted either by volcanism or by asteroid impact. It turns out that the rocks of the highlands, the lighter area on the Moon where most of the craters are, date to close to 4.5 billion years, and are probably the original crust of the Moon. The rocks from the lunar maria or seas are younger from about 4.1 billion years down to 3.8 billion years. So they were thought to be caused by asteroid impacts from the Late Heavy Bombardment.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
The Late Heavy Bombardment is not accepted by all planetary scientists. The main evidence is the cratering and maria on the Moon.
Ephemeris: 02/06/2025 – The Moon tonight, two days after first quarter
This is Ephemeris for Thursday, February 6th. Today the Sun will be up for 10 hours and 3 minutes, setting at 5:59, and it will rise tomorrow at 7:54. The Moon, 1 day past first quarter, will set at 4:30 tomorrow morning.
Tonight the moon will be about a day and a half past first quarter it is showing some very nice craters for the binoculars or small telescope. Near the south end of the moon near the terminator, the sunrise line, is the crater called Clavius which has an arc of several craters within it, each of decreasing size. North or above that is the sharp-edged crater called Tycho which, during a full moon, shows several long ejecta rays across the face of the Moon, but are almost invisible now. Near the top edge of the Moon the flat floored crater called Plato is seen by the edge of the large sea Mare Imbrium or Sea of Showers. A mountain range at the opposite side of Imbrium is called the Apennines Mountains.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Bob Moler's Ephemeris Blog 