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.

04/22/2021 – Ephemeris – Earth Day

April 22, 2021 Comments off

This is Bob Moler with Ephemeris for Earth Day, Thursday, April 22nd. Today the Sun will be up for 13 hours and 50 minutes, setting at 8:37, and it will rise tomorrow at 6:44. The Moon, 2 days past first quarter, will set at 5:24 tomorrow morning.

The Earth is unique in the solar system. Actually every planet is unique, as we’ve found out with our spacecraft that have at least flown by every planet of the solar system, plus the dwarf planets Pluto and Ceres. But the Earth uniquely supports life as we know it. It’s the only one that we know of. It is imperative that we colonize the Moon, Mars and asteroids and live off the land, so no single disaster can wipe the human race out. However, we need to take care of the Earth, to understand and get a grip on what we’re doing to Earth’s climate. We must think of the Earth as a spaceship with both renewable resources and limited ones. Our journey is long, and the supplies will have to last. So support your local planet!

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

Addendum

The Earth from the DSCOVR satellite orbiting the Sun-Earth L1 point The image was taken two days ago. Credit NOAA.
Categories: Earth, Ephemeris Program Tags:

04/21/2021 – Ephemeris – Let’s search for the naked-eye planets for this week

April 21, 2021 Comments off

This is Ephemeris for Wednesday, April 21st. Today the Sun will be up for 13 hours and 47 minutes, setting at 8:35, and it will rise tomorrow at 6:46. The Moon, 1 day past first quarter, will set at 4:56 tomorrow morning.

Let’s search for the naked-eye planets for this week. Unfortunately the only one you’ll find in the evening is Mars. It can be found in the west at 10 pm tonight, between the constellations of Taurus the bull below and Gemini the twins above. Tonight it’s just off Castor’s big toe. Mars will set at 1:30 am. Venus is now just east of the Sun, setting 31 minutes after sunset. It will be late May or early June before it will be easily spotted in the evening twilight. Mercury is between the Sun and Venus. Saturn and Jupiter are at a far enough angle from the Sun to be spotted in the morning twilight. Saturn will rise at 3:51 am, with Jupiter rising at 4:28 am. By 6 am they will be low in the southeast.

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

Addendum

Mars and the Moon with the fleeing stars of winter tonight at 10 pm, April 21, 2021. Created using Stellarium.
The moon as it might appear tonight, April 21, 2021. Created using Stellarium.
Jupiter and Saturn in the morning twilight tomorrow morning, April 22, 2021. Created using Stellarium.
Saturn and Jupiter as seen in a small telescope at the same magnification. Apparent diameters: Saturn, 16.46″, rings, 38.36″; Jupiter, 36.55″. Mars is too far away to make out detail on its surface, except maybe a polar cap. Its apparent diameter is 4.81″. The ” symbol means seconds of arc (1/3600th of a degree.) Created using Cartes du Ciel (Sky Charts).
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on April 21, 2021. The night ends on the left with sunrise on the 22nd. Click on the image to enlarge. Created using my LookingUp program.

04/20/2021 – Ephemeris – SpaceX gets NASA contract for Human Landing System for the Artemis (Moon) Program

April 20, 2021 Comments off

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

SpaceX Concept lunar Lander as of 04/16/2021
SpaceX’s updated concept of their Starship lunar lander as of 04/16/2021. Credit: SpaceX.

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

April 19, 2021 Comments off

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

The Moon as it should appear at 10 pm tonight, April 19, 2021. Can you see the rabbit’s head? Created using Stellarium.
Yutu, the Jade Rabbit pounding medicine, as he appears in the lunar seas on a full moon. Rotated to fit tonight’s moon orientation. Via Wikipedia, no source provided.

04/16/2021 – Ephemeris – Virtual Star Party for the Sleeping Bear Dunes tonight

April 16, 2021 Comments off

This is Bob Moler with Ephemeris for Friday, April 16th. Today the Sun will be up for 13 hours and 33 minutes, setting at 8:29, and it will rise tomorrow at 6:54. The Moon, 4 days before first quarter, will set at 1:15 tomorrow morning.

Tonight the Sleeping Bear Dunes National Lakeshore and the Grand Traverse Astronomical Society will hold an online star party this evening starting around 9 pm via the Zoom app available for Android smartphones, iPhones and computers. Instructions for joining are on the society’s website http://www.gtastro.org or the Sleeping Bear Dunes National Lakeshore Facebook page. Images will be captured live, if it’s clear, from Northwestern Michigan College’s Joseph H Rogers Observatory. The images will be pretty much what is seen at the telescope eyepiece, and definitely not Hubble Space Telescope quality, which take days to process. Visible will be the crescent Moon. Then we move out beyond the solar system into our galaxy for star clusters and beyond our galaxy into the distant galaxies of spring skies.

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. We’ll be looking at the Moon’s dark lava seas and other craters near the sunrise terminator.

We will be looking also at a few star clusters and out the thin side of our Milky Way Galaxy to lots of other galaxies.

04/15/2021 – Ephemeris – The Moon tonight – libration

April 15, 2021 Comments off

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

Moon's libration animation
Simulation of the Moon’s phase and libration for October 2007 by Tomruen. Image is in the Public Domain. I recognize the animation, and it can be produced using the free app Virtual Moon Atlas. A link to the app is seen in the column to the right.

04/14/2021 – Ephemeris – Let’s search for the naked-eye planets for this week

April 14, 2021 Comments off

This is Bob Moler with Ephemeris for Wednesday, April 14th. Today the Sun will be up for 13 hours and 27 minutes, setting at 8:27, and it will rise tomorrow at 6:58. The Moon, 3 days past new, will set at 11:11 this evening.

Let’s search for the naked-eye planets for this week. Unfortunately the only one you’ll find in the evening is Mars. It can be found in the west at 10 pm tonight, between the constellations of Taurus the bull below and Gemini the twins above. Mars will set at 1:39 am. Venus is now just east of the Sun, setting 23 minutes after sunset. It will be late May or early June before it will be easily spotted in the evening twilight. The other three naked-eye planets are west of the Sun in the morning sky. Only Saturn and Jupiter are at a far enough angle from the Sun to be spotted in the morning twilight. Saturn will rise at 4:17 am, with Jupiter rising at 4:53 am. By 6 am they will be low in the southeast.

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

Addendum

Mars and the Moon finder
Mars and the Moon finder with the fleeing star of winter in the western sky near the end of twilight. The time will be 10 pm, April 14, 2021. The Moon is an actual crescent as seen below. Created using Stellarium.
Binocular Moon
The crescent Moon showing earth shine at 10 pm April 14, 2021. Created using Stellarium.
Jupiter and Saturn Jupiter ans Saturn in the morning
Jupiter and Saturn low in the southeastern sky at 6 am, about an hour before sunrise tomorrow morning April 15, 2021. Created using Stellarium.
Jupiter and Saturn through a telescope
Jupiter and Saturn as seen in a small telescope at the same magnification. Apparent diameters: Jupiter, 35.90″; Saturn, 16.27″, rings, 37.91″. Mars is too far away to make out detail on its surface, except maybe a polar cap. Its apparent diameter is 4.96″. The ” symbol means seconds of arc (1/3600th of a degree.) Created using Cartes du Ciel (Sky Charts).
The Moon and planets on a single night
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on April 14, 2021. The night ends on the left with sunrise on the 15th. Click on the image to enlarge. Created using my LookingUp program.