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07/16/2021 – Ephemeris – The best time to see detail on the Moon (IMHO)

July 16, 2021 Comments off

This is Ephemeris for Friday, July 16th. Today the Sun will be up for 15 hours and 11 minutes, setting at 9:24, and it will rise tomorrow at 6:13. The Moon, 1 day before first quarter, will set at 1:08 tomorrow morning.

I consider the week centered on the first quarter moon to be the best time to view the Moon in a telescope. The best part of the Moon to view is near the terminator. The terminator is the sunrise line on the moon that we see before full moon, and the sunset line we see after full moon. The terminator is where the shadows are longest on the Moon and indeed on the Earth, with the low Sun in the sky. The Moon has lots of craters in its south or bottom part. We call that the lunar highlands, which is completely saturated with craters. Personally, I like craters. The darker lava plains that were initially called seas (the name stuck). They are flat and nearly featureless unless seen very close to the terminator, where the slight wrinkle ridges can be spotted.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

The Moon tonight

The Moon tonight at 11 pm, July 16, 2021, about a day and 7 hours before the instant of first quarter. Note the shadows that bring out the craters near the terminator. Created using Stellarium.

Wrinkle ridges

Wrinkle ridges on the floor of a lunar sea (lava plain). These are only visible at a very low sun angle near the terminator. I can find no information on this image, but apparently it was taken in lunar orbit. This is much sharper detail than can be seen from earth.

 

07/15/2021 – Ephemeris – What the Chinese saw in the face of the Moon

July 15, 2021 Comments off

This is Bob Moler with Ephemeris for Thursday, July 15th. Today the Sun will be up for 15 hours and 13 minutes, setting at 9:25, and it will rise tomorrow at 6:12. The Moon, 2 days before first quarter, will set at 12:45 tomorrow morning.

Looking at the Moon tonight with the naked eye or binoculars, the dark patches called seas, which are really lava filled plains, make out the ears, head, and top part of the body of a rabbit that appears upside down. It’s the Chinese Jade Rabbit, Yutu. The seas involved, with their English names are: Serenity, the top of its body; Tranquility, its head; the more prominent ear is Fertility; while the other ear is a combination of the Bay of Roughness and Sea of Nectar. Yutu is the pet rabbit of the Moon goddess Chang’e, who flew to the Moon to escape her pursuers. The Chinese space agency has named all their moon landers Chang’e and their lunar rovers Yutu in their honor.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.

Addendum

The Moon tonight with the Jade Rabbit

The Moon tonight with the Jade Rabbit delineated in the seas and one bay the dark lava covered plains of the Moon. Created using Stellarium.

The Jade Rabbit seen on a full moon

The Jade Rabbit seen on a full moon rotated close to what tonight’s Moon is. Actually, the ancient Chinese saw the rabbit pounding medicine.

06/17/2021 – Ephemeris – Congress approves more money for NASA’s lunar lander

June 17, 2021 Comments off

This is Bob Moler with Ephemeris for Thursday, June 17th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:31, and it will rise tomorrow at 5:56. The Moon, at first quarter tonight, will set at 2:18 tomorrow morning. | Tonight’s Moon will be almost exactly cut in half by the sunrise terminator, since the precise moment of first quarter will be at 11:54 this evening. Speaking of the Moon, Congress has approved NASA spending of 10 billion dollars over 5 years on the Human Lander System for the Artemis Moon program. This would allow more than one bidder to win the lander contract. SpaceX’s Lunar Starship was the only one to win a contract. NASA and Congress wanted two to win, but couldn’t afford more than SpaceX. Now comes the rub… Congress will have to appropriate the money out of the budget every year for this. The target date for the first landing is 2024, which I’m pretty sure is already out of reach.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4). They may be different for your location.

Addendum

First Quarter Moon with binoculars or low power telescope

First Quarter Moon with binoculars or low power telescope as it might appear tonight at 11 pm. Created using Stellarium.

Three Lunar Lander proposals

Three Lunar Lander proposals. Credit Dynetics, SpaceX, and Blue Origin. Credit NASA.

Also, SpaceX’s bid was the lowest by a wide margin. With the extra funds, it looks like Blue Origin will be the second successful bidder.

06/14/2021 – Ephemeris – Images of the Moon: Then and now

June 14, 2021 Comments off

This is Bob Moler with Ephemeris for Flag Day, Monday, June 14th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:29, and it will rise tomorrow at 5:56. The Moon, 3 days before first quarter, will set at 1 am.

The waxing crescent Moon shows its cratered highlands and flat lava plains that early telescopic astronomers fancied as water filled and called them seas, so the nomenclature stuck, and we call them seas to this day. When I grew up in the 1950s I was captivated by the moonscapes painted by Chesley Bonestell with their sharp rugged mountain peaks. The actual lunar landscape turned out to be softer, more rounded. The Earth’s surface features are younger than the Moon’s due to plate tectonics, something few geologists in the 1950s believed in. The Moon’s features are generally billions of years old and erosion by meteoroid impacts and ejecta have covered the landscape with a fine dust, over the eons, that smooths out its features.

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

Addendum

Chesley Bonestell moonscape

A Chesley Bonestell moonscape. Note the sharp detail including an arch at center right and an overhang at right. Such was the state of our ignorance before spacecraft like Ranger, Surveyor, Lunar Orbiter and Apollo reached the Moon. Click on the image to enlarge. Credit Chesley Bonestell.

Moonscape photographed by JAXA (Japan) spacecraft Kaguya

Moonscape photographed by JAXA (Japan) spacecraft Kaguya with about the same orientation as the Bonestell painting, except from orbit. Click on the image to enlarge. Credit JAXA/NHK.

Image from Apollo 17 showing lunar erosion

Image from Apollo 17 showing lunar erosion. Even the rocks in the foreground show that they were eroded. The image also shows astronaut Dr. Harrison “Jack” Schmidt. Click on the image to enlarge. Credit NASA.

06/11/2021 – Ephemeris – Spotting the one-day-old Moon

June 11, 2021 Comments off

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 ecliptic June 11, 2021

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.

Sunset ecliptic in March

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

May 21, 2021 Comments off

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

Apparent paths of the Sun and Moon against the sky
A diagram of the paths of the Moon and Sun projected on the sky (celestial sphere). N1 and N2 are the nodes (crossing points). Nodes are ascending or descending depending on the northerly or southerly component of the Moon’s motion in crossing them. The Sun and Moon move in an easterly direction, but the Moon’s orbit precesses so that the line of nodes move in a westerly direction once around in 18.6 years. That’s why eclipse season intervals are 173.3 days and move backward in the calendar one year to the next. Eclipse seasons occur when the Sun is less than about 17.5 degrees from a node. Credit Earthsky.org.

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

May 17, 2021 Comments off

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

The crescent Moon and the Beehive star cluster
The crescent Moon and the Beehive star cluster, below left of center as they might be seen in binoculars tonight, May 17, 2021 at 10 pm. The Beehive is also known as Messier 44 or M 44. The star cluster is visible to the naked eye, but it stars are not resolvable, so it looks like a small glowing patch. It was known as Praesepe, the manger. The star just left of the Moon and another just left of the Beehive are Asellus Borealis and Asellus Australis respectively, the North and South Donkeys. They are feeding at the manger. The donkey stars and the Beehive are in the central part of the constellation of Cancer the crab. The image was created using Stellarium.
The Moon a10 pm May 17, 2021 as seen in a low power telescope with the lunar seas labeled in English, rather than Latin. The seas are easily visible in binoculars. Created using Stellarium and GIMP.

04/27/2021 – Ephemeris – What is the opposite of the Harvest Moon effect?

April 27, 2021 Comments off

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

The motion of the moon
The motion of the moon near the Harvest Moon as it rises from night to night. This is looking east at where the Moon will rise, and we’re able to see below the horizon. The celestial equator, a projection of the Earth’s equator on the sky cross the horizon at an angle equal to 90 minus one’s latitude. Around my location that’s 45.5 degrees. The Moon will rise parallel to the celestial equator. Its daily orbital motion is at the shallow angle of 5 degrees. So the advance in rise times starts off at 20 minutes later each night, rather than the average 50 minutes.
Spring Moon rising angle
How the Moon’s path near a spring full moon affects its rise time interval. Note the scale is not the same as the top image. Created using Cartes du Ciel (Sky Charts).

04/26/2021 – Ephemeris – There’s a full supermoon tonight

April 26, 2021 Comments off

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

High contrast full Moow
The full Moon 7 hours before it was officially full. The contrast was greatly enhanced to bring out Tycho’s ray system. The crater Tycho is at the south part of the Moon and appears bright with a dark ring around it. Credit Bob Moler.
Tycho and Kepler
Tycho and Kepler. Artist for Tycho: Eduard Ender (1822-1883). Artist for Kepler, unknown. Source: Wikipedia

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

April 23, 2021 Comments off

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

The Moon tonight
The Moon as it might be seen in a small telescope tonight, April 23, 2021 at 10 pm. Created using Stellarium.
Aristarchus close up
The impact crater Aristarchus, in the center, is 24 miles or 40 kilometers in diameter and approximately 450 million years old. Credit: Lunar and Planetary Institute.