Archive
06/11/2021 – Ephemeris – Spotting the one-day-old Moon
This is Bob Moler with Ephemeris for Friday, June 11th. Today the Sun will be up for 15 hours and 31 minutes, setting at 9:28, and it will rise tomorrow at 5:56. The Moon, 1 day past new, will set at 10:56 this evening.
Tonight the thin crescent Moon, some 40 hours old, or more properly 40 hours from eclipsing the Sun, will be to the right and a bit below the bright planet Venus. It might be possible to spot it. I do remember spotting the tiny sliver of a Moon the next evening after a solar eclipse in 1970. But that was in March*, when the ecliptic, the path of the Sun and near the path of all the planets and the Moon, was angled more vertically than it is this time of year. That means that the Moon and planets, when near the Sun, are lower in the sky after sunset than they would be in late winter and early spring. Venus is slowly moving away from the Sun, from our vantage point, while Mars, above and left of it, is slowly retreating toward the Sun. Their apparent paths will cross on July 13th.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
* On the program, I mistakenly said April.
Addendum
Sunset sky and ecliptic (orange line) 45 minutes after sunset tonight, June 11, 2021. Note the low angle of the ecliptic, the apparent path of the Sun and near the path of the planets. The angle will get even lower as summer progresses. So planets close to the Sun will set shortly after the Sun. Created using Stellarium.
This is the sky one day after the March 7, 1970 eclipse and 45 minutes after sunset. Being March, note how steep the angle of the ecliptic, so planets close to the Sun are higher in the sky. Also, twilight ends quicker in March than in June.
05/21/2021 – Ephemeris – For everything there is a season… even eclipses
This is Ephemeris for Friday, May 21st. Today the Sun will be up for 15 hours and 3 minutes, setting at 9:11, and it will rise tomorrow at 6:07. The Moon, 2 days past first quarter, will set at 4:14 tomorrow morning.
There are seasons for everything: baseball season, football season, spring, summer, what have you. There are also eclipse seasons. The Moon’s orbit is tilted by about 5 degrees to the ecliptic, the path of the Sun in the sky. The points where they cross are called nodes, 180 degrees apart. When the Sun is near one of those nodes we are in an eclipse season, where a solar eclipse can occur at new moon, and a lunar eclipse can occur at full moon. We are guaranteed one of each per eclipse season, and on rare occasions a third eclipse. Of course one has to be at the right place to see an eclipse. This eclipse season we will be at a marginal place to see both eclipses. Both are at sunrise, so we’ll see just a part of each of them.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
For a more extensive treatment of this subject check out: https://earthsky.org/astronomy-essentials/definition-what-is-an-eclipse-season
05/17/2021 – Ephemeris – The Moon tonight
This is Ephemeris for Monday, May 17th. Today the Sun will be up for 14 hours and 54 minutes, setting at 9:06, and it will rise tomorrow at 6:11. The Moon, 2 days before first quarter, will set at 2:25 tomorrow morning.
The Moon tonight reveals a bit more territory than it did last night, and will every night until full moon. The Moon’s solar day equals a lunar month of about 29 and a half of our days. As seen in binoculars, below and left of The distinctly oval Sea of Crises, or Mare Crisium, is the Sea of Fertility, or Mare Fecunditatis. To the left of the Sea of Crises, the Sea of Tranquility (Tranquilitatis) where the Apollo 11 crew landed. Above that half of Sea of Serenity has come into daylight. Tonight the Beehive star cluster will be visible below and left of the Moon. It should be easily visible in binoculars and has a vaguely triangular shape. It was known to the ancients as Praesepe, the manger, who saw it as a glowing spot on moonless nights.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
04/27/2021 – Ephemeris – What is the opposite of the Harvest Moon effect?
This is Bob Moler with Ephemeris for Tuesday, April 27th. Today the Sun will be up for 14 hours and 4 minutes, setting at 8:43, and it will rise tomorrow at 6:36. The Moon, 1 day past full, will rise at 9:43 this evening.
Let’s think back to last fall and the Harvest Moon. The big deal about the Harvest Moon is the Moon lingers, rising or being bright in twilight to help illuminate the harvesters of old by effective lengthening the effects of daylight. The spring bright Moon after full moon rises much later night to night. Six months ago the difference in the rise times of the Moon between the full moon and the next day was 20 minutes. Today the Moon will rise 96 minutes later than it did yesterday. The reason is the beside moving eastward, it is also moving southward to where the Sun was in late fall. So it rises much later each night than it did after full moon last fall. As it is the dark skies are moving to later and later in the evening due to the spring season and daylight time.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
04/26/2021 – Ephemeris – There’s a full supermoon tonight
This is Ephemeris for Monday, April 26th. Today the Sun will be up for 14 hours and 2 minutes, setting at 8:41, and it will rise tomorrow at 6:38. The Moon, at full today, will rise at 8:19 this evening.
The full moon tonight is the full Pink Moon, and a supermoon. As down as I am about full moons due to the fact that they light up the sky and flood out the dimmer objects in the sky, I once in a while stop and view it. The time of the full moon is 11:31 tonight, so when it rises tonight we will be looking at the moon from very nearly the direction of the Sun, so there will be few shadows to be had. The crater Tycho is near the bottom or south end of the moon and has long rays of tiny ejecta craters. The full moon is the best time to see these rays, which are easily visible in binoculars, through which Tycho itself looks like a bright dot. In telescopes Tycho looks like a small bright crater with a dark ring around it. The full moon is super bright. It’s daytime over there.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Tycho Brahe and Johannes Kepler are inexorably linked in astronomical history. Tycho was famously stingy with the results of his observations. It was only after his death that Kepler was able to have access to them. Mars was the planet that was hardest to model in both the Ptolemaic geocentric and Copernican heliocentric universes, since both assumed the planetary orbits were circular. So both resorted to epicycles in an attempt to tweak their models in an attempt to fit with observational reality.
Both Tycho and Kepler have craters named for them on the Moon. Tycho gets a splashy crater on the southern part of the Moon. Kepler, however, gets a small crater on the plains of Oceanus Procellarum west of the crater Copernicus on the left side of the Moon, as we see it
04/23/2021 – Ephemeris – The gibbous Moon tonight
This is Ephemeris for Friday, April 23rd. Today the Sun will be up for 13 hours and 53 minutes, setting at 8:38, and it will rise tomorrow at 6:43. The Moon, halfway from first quarter to full, will set at 5:49 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 upper left edge of the moon near the terminator is a bright spot visible in binoculars. In a telescope it is a crater called Aristarchus. It is a fairly new crater, probably 450 million years old. As a rule the brighter the crater the newer it is. Aristarchus is the brightest spot on the moon when it is seen during a full moon. Over the years visual astronomers have seen hazes and bright spots from time to time in and near Aristarchus.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
04/20/2021 – Ephemeris – SpaceX gets NASA contract for Human Landing System for the Artemis (Moon) Program
This is Bob Moler with Ephemeris for Tuesday, April 20th. Today the Sun will be up for 13 hours and 44 minutes, setting at 8:34, and it will rise tomorrow at 6:47. The Moon, at first quarter today, will set at 4:24 tomorrow morning.
Late last week NASA announced that it had selected SpaceX to provide the Human Lander System for the Artemis program. That lander is the lunar variant of the Starship SpaceX is currently testing near Boca Chica, Texas, just north of the mouth of the Rio Grande. A Starship consists of two stages: a booster called Super Heavy and the Starship upper stage. The Super Heavy returns to the launch site, while the Starship must be refueled several times in orbit to be able to head on out to the Moon. The astronauts would be launched as planned in an Orion capsule with the Space Launch System, then transfer the astronauts to the Starship waiting in lunar orbit or from the Lunar Gateway also in lunar orbit for the trip down to the lunar surface.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
NASA’s Source Selection Document (the rationale for their selection): https://www.nasa.gov/sites/default/files/atoms/files/option-a-source-selection-statement-final.pdf
04/19/2021 – Ephemeris – The Moon tonight, Yutu the Jade Rabbit
This is Ephemeris for Monday, April 19th. Today the Sun will be up for 13 hours and 42 minutes, setting at 8:33, and it will rise tomorrow at 6:49. The Moon, 1 day before first quarter, will set at 3:47 tomorrow morning.
Let’s take a look at the Moon tonight. Binoculars or a small telescope will be handy for seeing the lunar features. The Moon will be at actual first quarter at 3 am tomorrow morning so the terminator or in this case sunrise line on the Moon will cut it nearly in half. To the naked eye the face of the Man in the Moon isn’t yet noticeable, but the top part of the upside down Chinese rabbit Yutu can be glimpsed. His ears are the seas of Fertility and Nectar, his head is the Sea of Tranquility, and the top part of his body is the Sea of Serenity. The lower part of his body and his arms pulverizing medicine with a mortar and pestle will have to wait until the Moon is nearer full. Yutu is the pet rabbit of the Chinese Moon goddess Chang’e.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
04/15/2021 – Ephemeris – The Moon tonight – libration
This is Bob Moler with Ephemeris for Thursday, April 15th. Today the Sun will be up for 13 hours and 30 minutes, setting at 8:28, and it will rise tomorrow at 6:56. The Moon, 4 days past new, will set at 12:14 tomorrow morning.
The crescent Moon tonight is in the constellation of Taurus the bull. The bright star Aldebaran will be just to the left of the Moon. In binoculars the dark oval spot visible on the Moon is the Sea of Crises or Mare Crisium a small dark lava plain. The Moon’s rotation is quite uniform, however its orbit isn’t circular, so the Moon’s appearance seems to rock a bit back and forth over the month. It’s an effect called libration. And one way to track that is to note how close the Sea of Crises is to the edge of the Moon. A week from now that sea will appear its closest to the edge. Astronomers call the edge of the Moon the limb. The phase line between day and night on the Moon is called the terminator. Now as the Moon is waxing, it is the morning or sunrise terminator.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
04/06/2021 – Ephemeris – The spring constellation of Leo
This is Bob Moler with Ephemeris for Tuesday, April 6th. Today the Sun will be up for 13 hours and 3 minutes, setting at 8:17, and it will rise tomorrow at 7:12. The Moon, 2 days past last quarter, will rise at 5:48 tomorrow morning.
Tomorrow morning early risers will see the Moon near the planets Saturn and Jupiter. Specifically Jupiter, left of Saturn will be right above the waning crescent Moon.
Tonight however, will be a good time to check out Leo the celestial lion high in the southeast. His distinctive pattern of stars is a backward question mark, with the bright star Regulus as the dot on the bottom of it. It delineates the male lion’s head and mane. That pattern is also called the Sickle. While Leo is one of the official 88 constellations, the Sickle is an asterism, or informal constellation. Completing Leo is a triangle of stars below left of Regulus, his rump ending with the star Denebola, at the root of Leo’s tail. Leo is rich in mythology.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addenda
Jupiter and the Moon tomorrow morning
Leo tonight
Bob Moler's Ephemeris Blog 