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03/11/2019 – Ephemeris – The Moon: Dark side, far side, which is it?
Ephemeris for Monday, March 11th. Today the Sun will be up for 11 hours and 40 minutes, setting at 7:43, and it will rise tomorrow at 8:01. The Moon, 3 days before first quarter, will set at 12:54 tomorrow morning.
Tonight the Moon is at its crescent phase, meaning it is slightly closer to the Sun than the Earth is. Most of the Moon we see is in night. Some earth shine may be seen on its night side due to the big nearly full Earth shining on it. I get ticked sometimes when someone who knows better, especially in the media, mentions the dark side of the Moon when they should use the term far side, the part of the Moon that permanently faces away from the Earth. When the Chinese Chang’e 4 spacecraft landed on the far side of the Moon recently many headlines proclaimed that it landed on the dark side of the Moon. The Moon has a night side, as does the Earth, but that changes as the Moon rotates in the sunlight. And the Moon does rotate. It happens to be in sync with its revolution about the Earth.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The crescent Moon tonight at 9 p.m. EDT, March 11, 2019. Created using Stellarium.
Demonstration of the Moon’s crescent phase with the Styrofoam moon ball we use for Project Astro held up to a light off frame to the right. The night side of the ball is illuminated a bit by the translucency of the ball, and the reflection off my hand. Note the roughness of the ball is visible only at the terminator.
The Earth and Moon if seen as a crescent, near side, far side, sunlit side and earth shine. Credit: me.
10/12/2018 – Ephemeris – The Moon’s phases
Ephemeris for Friday, October 12th. The Sun will rise at 7:54. It’ll be up for 11 hours and 8 minutes, setting at 7:03. The Moon, halfway from new to first quarter, will set at 9:31 this evening.
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 halfway 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. Sometimes, 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.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
09/25/2018 – Ephemeris – The harvest moon effect
Ephemeris for Tuesday, September 25th. The Sun will rise at 7:33. It’ll be up for 12 hours and 1 minute, setting at 7:34. The Moon, 1 day past full, will rise at 8:17 this evening.
The full, or nearly full moon, just rising, looks like a large orange pumpkin. The color, like the red of the sunset is caused by the scattering out of blue light by the atmosphere. It can happen at any full moon, not just the Harvest Moon, which was officially yesterday. What the Moon around the Harvest Moon does do is rise only a little later each evening. This helped the farmers in earlier times extend daylight to bring in the crops. On average the moon rises or sets 50 minutes later each night. However when the Moon is in the part of the sky where it is moving northward as well as eastward, then it rises only a little later each night. Tomorrow’s Moon will rise only 27 minutes later than it will this evening.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
09/13/2018 – Ephemeris – The Man in the Moon’s eye
Ephemeris for Thursday, September 13th. The Sun will rise at 7:19. It’ll be up for 12 hours and 37 minutes, setting at 7:57. The Moon, 3 days before first quarter, will set at 10:27 this evening.
The Moon tonight is a 4 day old moon, and appears near the planet Jupiter. Day one is its first appearance in the evening after disappearing from the morning sky. The ancients called it the new moon, but astronomers treat the conjunction of the Moon and the Sun as the new moon. In this program I note the days before or after the nearest quarter phase, as a better representation of the actual appearance of the Moon’s phase. The Moon will be a beautiful crescent tonight. Binoculars will reveal a dark area just above the fattest part of the crescent. It serves as one of the Man in the Moon’s eyes. Its official name is Mare Crisium, or Sea of Crises. Most of the Moon’s seas are connected, or appear to be. This one is definitely not.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The 4 day old Moon showing Mare Crisium, the Sea of Crises. 9 p.m. September 13, 2018. Created using Virtual Moon Atlas.
09/11/2018 – Ephemeris – Earth shine on the Moon
Ephemeris for Tuesday, September 11th. The Sun will rise at 7:16. It’ll be up for 12 hours and 43 minutes, setting at 8:00. The Moon, 2 days past new, will set at 9:27 this evening.
At around 8:30 this evening Venus will be in the southwest only 9 degrees above the horizon, about the width of a fist held at arm’s length. While viewing Venus the Moon will be to the right and above our evening star. It will be a thin sliver of a crescent and in the twilight there will be the suggestion that there is more than the thin sliver of the Moon visible. Binoculars will confirm that the entire disk of the Moon will be visible. The effect is called earth shine. The nearly full Earth is illuminating the Moon to a much greater degree than the full Moon illuminates the Earth. The Earth is about 4 times the Moons diameter and its surface is about twice as bright and the Moon’s. The ancients called it: “The old Moon in the new Moon’s arms.”
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Venus, the Moon and Jupiter at 8:30 p.m. September 11, 2018. Created using Stellarium.
An overly colored Moon to bring out Earth shine on thye evening of September 11, 2018. Created by Stellarium. Overly processed in GIMP.
08/16/2018 -Ephemeris – The Moon’s phase, a closer look
Ephemeris for Thursday, August 16th. The Sun rises at 6:46. It’ll be up for 14 hours exactly, setting at 8:46. The Moon, 2 days before first quarter, will set at 11:59 this evening.
With the Moon at a fat crescent tonight, it’s a good time to turn binoculars or a small telescope toward it. The demarcation between the bright part and the dark part is called the terminator. In the case before full moon, it is the sunrise line. After that the sunset line. The Moon’s entire day lasts about 29 ½ earthly days. I am sometimes asked “What’s blocking the light from the unlit side of the Moon?” It’s the Moon itself. It’s the night side of the Moon, just as when we are in night. The Earth itself is blocking the Sun’s light from us. The Moon, like the Earth and all the other planets are spheres lit on one side by the Sun. It’s near the terminator of the Moon where the most detail is revealed by the long shadows cast by the Moon’s features.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The crescent moon as it should appear tonight. Created using Stellarium. Stellarium always shows details on the night side of the Moon. The crescent phase of the Moon is now too fat to really see earthshine on it’s night side.
Demonstration of the Moon’s crescent phase with the Styrofoam moon ball we use for Project Astro held up to a light off frame to the right. The night side of the ball is illuminated a bit by the translucency of the ball, and the reflection off my hand. Note the roughness of the ball is visible only at the terminator.
05/26/2017 – Ephemeris – Can you spot the extremely young Moon tonight?
Ephemeris for Friday, May 26th. Today the Sun will be up for 15 hours and 11 minutes, setting at 9:15, and it will rise tomorrow at 6:03. The Moon, 1 day past new, will set at 10:16 this evening.
It’s spring and a great time to see if you can spot the young moon. The official time when the moon was new was 3:44 p.m. yesterday afternoon (19:44 UT 25 May 2017), which would make the moon a bit less than 31 hours old if spotted before it sets an hour after the Sun. This requires crystal clear skies and a very low northwestern horizon. Binoculars are a definite help. Spotting the earliest moon after new moon is one of the challenges amateur astronomers pit their observing skills with. Another is the Messier Marathon, in which one tries to observe all 110 of Charles Messier’s catalog entries of dim objects on a single night, which is theoretically possible around March 24th.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
A 39 hour old Moon with Jupiter taken by Greg Hogan on September 2, 2016.
I got this from EarthSky.org. Here’s a search I made of the young moon that has some other images: http://earthsky.org/?s=young+moon
05/02/2017 – Ephemeris – Puzzling out the Moon’s history
Ephemeris for Tuesday, May 2nd. The Sun rises at 6:30. It’ll be up for 14 hours and 17 minutes, setting at 8:48. The Moon, at first quarter today, will set at 3:06 tomorrow morning.
The Moon will be at exactly first quarter at 10:47 p.m., so it should be split exactly in half by the sunrise line or terminator. On the illuminated face of the Moon can be seen the dark gray spots called seas. In dating the moon rocks brought back by the Apollo astronauts the dates tell the amount of time since the rocks were molten due to collisions. The dates turn out to give clues to when the seas were formed, because they are actually large impact craters, which were filled in by the lava from the moon’s interior. The oldest rocks on the Moon are 4.5 billion years old, dating from the formation of the Moon. There’s another group about 3.9 billion years old dating to when many of the seas were formed in a cataclysm called the late heavy bombardment.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
First quarter Moon with key to the lunar seas. Created using Stellarium.
Sym Latin Name English Name Age A Mare Serenitatis Sea of Serenity 3.85 to 3.92 billion years B Mare Tranquillitatis Sea of Tranquility 3.92 to 4.55 billion years C Mare Nectaris Sea of Nectar 3.85 to 3.92 billion years D Mare Fecunditatis Sea of Fertility 3.92 to 4.55 billion years E Mare Crisium Sea of Crises 3.85 to 3.92 billion years F Mare Frigoris Sea of Cold 3.85 to 4.55 billion years
Data are from Virtual Moon Atlas
04/03/2017 – Ephemeris – A two bit* Moon today
Ephemeris for Monday, April 3rd. The Sun will rise at 7:19. It’ll be up for 12 hours and 53 minutes, setting at 8:12. The Moon, at first quarter today, will set at 3:38 tomorrow morning.
The Moon will be at exactly first quarter at 2:12 this afternoon (18:12 UT). By this evening for us the terminator line, which is the sunrise line on the Moon as the Moon’s phase waxes will be bowed to the left a bit. The names of the primary phases of the Moon are a bit odd. The quarter moons are named for their positions one quarter or 90 degrees from the Sun. The full moon describes it appearance as fully illuminated. New moon is odd too. To the Jews and the Arabs the New moon was the name for the first sighting of the crescent Moon after it disappeared from the morning sky. Astronomers use that term today for when the Moon is in conjunction with the Sun, day zero of a lunation or lunar month, about a day before its first appearance in the evening.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
* If “two bit” is foreign to you. It dates back to US colonial times when the most prevalent coin around was the Spanish Dollar, also known as a piece of eight. A quarter of that was two bits, 25 cents in modern parlance. It lives on in the tune and knock sequence “Shave and a haircut, two bits” or five rapid knocks a pause and two more. See the movie “Who Framed Roger Rabbit?”.
Addendum
This is the best diagram of the Moon’s phases and how the it appears from the Earth. Credit http://planetfacts.org/phases-of-the-moon/ which I recommend.
However I do not like the label Dark Side. It is simply the night side. The Far Side is what many people mistakenly call the dark side, because we can never see it from the Earth. However the far side sees more sunlight than the near side. One, it is never darkened by an eclipse of the Moon, because it’s night-time there normally at that time. Two, at new moon it is fully facing the Sun, and also a quarter of a million miles closer to the Sun than the Earth is. So how can it be the dark side. Really. Come on people.
02/14/2017 – Ephemeris – Is the Moon waxing or waning?
Ephemeris for St Valentine’s Day, Tuesday, February 14th. The Sun will rise at 7:43. It’ll be up for 10 hours and 26 minutes, setting at 6:10. The Moon, half way from full to last quarter, will rise at 10:18 this evening.
This morning the waning gibbous moon will be a way to the right of the bright planet Jupiter which is in the southwest at 7 a.m. Tomorrow morning the Moon will appear above and right of Jupiter. My granddaughter is taking earth science in school now and is confused about when the Moon is waxing or waning. If it’s waxing it is getting fuller each night. If waning the Moon’s phase is getting thinner each night. But I told her that if you can see the Moon in the evening it’s waxing, and if you can see the Moon in the morning it’s waning. It works except around full Moon where you’d need a calendar for the full moon date or if it rises before or after sunset.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
A graphic explaining the Moon’s position with respect to the Earth and Sun (which is off the diagram to the right). The Moon orbits the Earth in a counterclockwise direction. Credit NASA/Bill Dunford.
Bob Moler's Ephemeris Blog 