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09/09/2022 – Ephemeris – Observe the Harvest Moon at the Sleeping Bear Dunes Saturday night (weather permitting)
Update 9/10/2022, 6 pm: The weather does not permit it! We’ll have another, again weather permitting, on September 24th. This time with dark skies and a look at the summer Milky Way, two days after the end of summer. (It still counts).
This is Ephemeris for Friday, September 9th. Today the Sun will be up for 12 hours and 49 minutes, setting at 8:04, and it will rise tomorrow at 7:15. The Moon, 1 day before full, will set at 7:14 tomorrow morning.
Tomorrow night, September 10th, there will be, weather permitting, a star party at Sleeping Bear Dunes National Lakeshore, this will take place at the Dune Climb. Actually, it will be mostly a Moon and planet party. The event will be made possible by the rangers of the park and the Grand Traverse Astronomical Society. The society’s and member’s telescopes will take over the parking lot closest to the Dunes. The event starts at 8 p.m., near sunset, while it’s still light out and the location can be found. The Moon will join the party, rising at 8:41 pm. Oh, and it’s a supermoon. There will be a short talk about Harvest Moon lore and why it was important. See if you can find the Man in the Moon and the Chinese rabbit pounding medicine.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.
Addendum
The Harvest Moon with Jupiter and Saturn at 9 pm, September 10, 2022. Created using Stellarium.
09/08/2022 – Ephemeris – We are going to have an early Harvest Moon this year
This is Bob Moler with Ephemeris for Thursday, September 8th. Today the Sun will be up for 12 hours and 53 minutes, setting at 8:06, and it will rise tomorrow at 7:14. The Moon, 2 days before full, will set at 5:54 tomorrow morning.
We are going to have an early Harvest Moon this year, on the early morning of Saturday the 10th, this Saturday coming up. The Harvest Moon is the closest full moon to the autumnal equinox, which is on the 22nd. The earliest a Harvest Moon can fall is on the 8th of September. The reason that the Harvest Moon is so famous is that at sunset the Moon’s path, in the sky, is shallow to the horizon. So it rises much less than its average 50 minutes later each night. This effectively lengthens the amount of useful twilight, allowing more time to harvest the crops. It compensated for the rapid retreat of the daylight hours this time of year. It’s not so important now, but back before electric lights it definitely was.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.
Addendum
The Harvest Moon rising as seen in Stellarium. The planetarium program Stellarium, which I use a lot, also colors the rising and setting Moon and Sun. It also reproduces the effect of atmospheric refraction, which makes objects close to the horizon look higher than they are. Thus, extended objects close to the horizon appear squashed a bit vertically.
The Harvest Moon effect is a phenomenon where the Moon’s nightly advance in rising times become much shorter than the average 50 minutes. This has the effect of extending the bright part of twilight for up to a week near the Harvest Moon. Complicating effects this year are the fact that the Harvest Moon is a supermoon, being a bit brighter than normal, and also moving faster than normal, negating the harvest moon effect somewhat. The Moon’s perigee was on the 7th, so the Moon is slowing down*, which shows in the delay numbers. Also helping to shorten the delay is that the path of the Moon is a bit shallower than the ecliptic. The Moon is south of the ecliptic, heading northward to its ascending node.
The Moon moves fastest in its orbit at perigee, and its slowest at apogee, at its farthest from the Earth.
09/20/2021 – Ephemeris – The Harvest Moon rises tonight
This is Ephemeris for Monday, September 20th. Today the Sun will be up for 12 hours and 15 minutes, setting at 7:43, and it will rise tomorrow at 7:29. The Moon, at full today, will rise at 8:03 this evening.
Tonight’s full moon is the Harvest Moon. It is the most famous of the named full moons, and was very useful in the days before electric lights. The reason is that the Moon, around the time it is full now, doesn’t advance its rising time very much from night to night, effectively extending the light of twilight to allow more time to gather in crops. This is because the Moon is moving north as well as eastward. The farther north it is, the longer it stays up and retards the advance in rise times. On average, the Moon rises 50 minutes later each night. This week, the interval is down near 20 minutes advance in moonrise times per day, extending twilight and the time each day to harvest the crops for a few more days.
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 autumn vs spring sunset ecliptic. I’m using the autumnal equinox 2021, with the tip of the spout of the Sagittarius Teapot at due south, and vernal equinox 2022, with the red star Betelgeuse in Orion at due south as examples. Click on the image to enlarge it. Created using Stellarium and GIMP.
The ecliptic for the autumnal equinox runs low in the south, a preview of the Sun’s apparent travel for the next six months of fall and winter. Besides the planets, the Moon at sticks close to that line, as do the planets. The full moon rising in the east as the Sun sets does so at a shallow angle, so for a week or so around the full moon, its advance in rise times can be as little as 20 minutes per night. In spring, it can be much longer than an hour.
09/29/2020 – Ephemeris – The Harvest Moon is in two days
This is Ephemeris for Tuesday, September 29th. Today the Sun will be up for 11 hours and 47 minutes, setting at 7:26, and it will rise tomorrow at 7:40. The Moon, 2 days before full, will set at 6:09 tomorrow morning.
This upcoming full moon is the Harvest Moon. It is the most famous of the named full moons, and was very useful in the days before electric lights. The reason is that the Moon, around the time it is full now doesn’t advance its rising time very much from night to night effectively extending the light of twilight to allow more time to gather in crops. This is because the Moon is moving north as well as eastward. The farther north it is the longer it stays up and retards the advance in rise times. On average the Moon rises 50 minutes later each night. This week the interval is down near 20 minutes advance in moonrise times per day extending twilight and the time each day to harvest the crops for a few more days.
The 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 from tonight through next Monday 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, crosses the horizon at an angle equal to 90 minus one’s latitude. Around my location that’s 45.5 degrees. The Moon and stars will rise parallel to the celestial equator. Its daily orbital motion is at the shallow angle of 5 degrees to the ecliptic, the apparent path of the Sun. So the advance in rise times starts off at 20 minutes later each night, rather than the average 50 minutes.
09/24/2018 – Ephemeris – The harvest moon and the Chinese Mid-Autumn Festival
Ephemeris for Monday, September 24th. The Sun will rise at 7:32. It’ll be up for 12 hours and 4 minutes, setting at 7:36. The Moon, at full today, will rise at 7:51 this evening.
Tonight at 10:53 p.m. the Moon will be full. And since it’s only two days past the autumnal equinox, this makes it the Harvest Moon. This full moon also marks the Chinese Mid-Autumn Festival to honor the Moon and the story of Chang’e a mortal woman to took an elixir and flew off to the Moon and became a goddess. Another story revolves around the Jade Rabbit pounding Medicine. I talked about the figure of a rabbit seen on the face of the Moon last Monday. He is a companion to Chang’e, and has a mortar on the Moon with him. He pounds out the medicine that makes the inhabitants of the sky immortal. The Chinese lunar probes are named Chang’e. Chang’e 3 landed on the Moon in 2013 and sent out a lunar rover named Yutu , the Jade Rabbit.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Chang’e 3 Lander on the Moon. Credit China National Space Administration 
Yutu Rover on the Moon. Credit China National Space Administration.
08/27/2018 – Ephemeris – It wasn’t the Harvest Moon but it has that effect
Ephemeris for Monday, August 27th. The Sun will rise at 6:59. It’ll be up for 13 hours and 29 minutes, setting at 8:28. The Moon, 1 day past full, will rise at 9:21 this evening.
Last night’s full moon wasn’t the Harvest Moon. That’s next month’s full moon. This full moon is the Sturgeon Full Moon. You’d think it should be the Corn Moon, That’s normally the September’s full moon, which is preempted this year by the Harvest Moon, the closest full moon to the autumnal equinox. What’s taking effect now is what I call the harvest moon effect, in that the nearly full Moon stays in the evening sky for almost a week, it seems, after full; while I’m waiting to spot the wonders of the summer Milky Way at a decent hour. On average the Moon rises about 50 minutes later each night. Now it’s decreasing to be less than 30 minutes. It won’t be until Thursday night that we’ll have a whole half hour of dark skies, and up to an hour by Friday night.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The motion of the Moon with respect to the eastern horizon from August 27 through August 31, 2018. It shows the difference in the rise times that create the harvest moon effect. Created using Cartes du Ciel (Sky Charts).
10/05/2014 – Ephemeris – The Harvest Moon
This is Bob Moler with Ephemeris for Thursday, October 5th. The Sun will rise at 7:45. It’ll be up for 11 hours and 29 minutes, setting at 7:15. The Moon, at full today, will rise at 7:38 this evening.
This is the day of the Harvest Moon. It will rise just before sunset and colored like a huge pumpkin. The huge size is an optical illusion, and the coloring is courtesy of our Earth’s atmosphere selectively bleeding out the blue from the Moon’s light. The reason the Harvest Moon is so special is that during this period the Moon rises for quite a few days just before and in twilight, effectively lengthening the hours of light that farmers can have to harvest their crops. Tomorrow the Moon will rise 32 minutes later than tonight, rather than the average 50 minutes. The effect is a bit diminished this year because the Moon is nearing perigee, its closest to the Earth and is traveling a bit faster than average. The Moon can get down to a 25 minute day-to-day difference.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The position of the Moon for 7 nights centered on moon rise tonight (10/04/2017). The rotation of the Earth carries the Moon to rise parallel to the green celestial equator line. The brown area at the bottom is below the horizon. Click on the image to enlarge. Created using Cartes du Ciel (Sky Charts).
08/08/2017 – Ephemeris – The Harvest Moon effect starts showing up 2 months early
Ephemeris for Tuesday, August 8th. The Sun rises at 6:37. It’ll be up for 14 hours and 20 minutes, setting at 8:58. The Moon, 1 day past full, will rise at 9:34 this evening.
The Harvest moon is nearly 2 months away, but some of its effects are starting to be felt now. I call it the Harvest Moon Effect. The Harvest Moon is a bit late this year, October 5th. It’s defined as the nearest full moon to the autumnal equinox. However from August to October the rising times of the full Moon and nights after for the next week don’t advance very fast. On average the Moon rises 50 minutes later each night. Between tonight and tomorrow night the interval will be 32 minutes. This is kind of a bummer this weekend when the Perseid meteor shower reaches peak. As with most meteor showers, the most meteors seen are after midnight. Saturday night’s Perseid peak has the Moon, six days after full rising at 11:36 p.m.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Moonrise time intervals for the rest of this week:
| Date | Moonrise | Difference |
| 08/08/17 | 9:34 p.m. | |
| 32 minutes | ||
| 08/09/17 | 10:06 p.m. | |
| 30 minutes | ||
| 08/10/17 | 10:36 p.m. | |
| 30 minutes | ||
| 08/11/17 | 11:06 p.m. | |
| 30 minutes | ||
| 08/12/17 | 11:36 p.m. | |
Harvest Moon Effect for this week. Note how shallow the path of the Moon is in relation to the eastern horizon. I’ve made the earth transparent so we can see the Moon below the horizon. As the Earth rotates the Moon will rise in a direction parallel to the celestial equator. In contrast the Moon’s path around March is steeper than average, so the interval in consecutive lunar rise times is much longer than the 50 minute average. Created using Cartes du Ciel (Sky Charts).
09/16/2016 – Ephemeris – The Harvest Moon is slightly eclipsed for everyone but the Americas
Ephemeris for Friday, September 16th. The Sun will rise at 7:23. It’ll be up for 12 hours and 27 minutes, setting at 7:50. The Moon, at full today, will rise at 7:59 this evening.
Tonight’s full Moon is the Harvest Moon, the nearest full Moon to the autumnal equinox. For the next few nights the Moon will rise later each night by much less than the average 50 minutes later each night effectively lengthening twilight for those gathering in crops. Also this afternoon there will be a penumbral lunar eclipse visible, well not here in Michigan… because the Moon won’t be up. Actually just about the whole world except North America and most of South America will be able to see the eclipse. A penumbral eclipse is what I call a 5 o’clock shadow eclipse. You wouldn’t know it unless someone pointed it out to you, when the Moon dips into the Earth’s outer shadow and the sunlight falling part of it is diminished by a little bit.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The not so full Moon of Monday night and its reflection on the waters of Suttons Bay after the schooner Inland Seas docked after an evening sail. Credit: the author.
The penumbral eclipse of the Moon centered on 2:25 p.m. Eastern time, 18:54 UT, for an hour and a half before and after. Only near the middle of the eclipse will anything be visible of the effect. I find that wearing sunglasses reduces the brightness of the moon and enhances the penumbral shadow. Credit: NASA/GSFC/ Fred Espenak.
For the full-page pdf of the above click here: http://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2016Sep16N.pdf
09/28/2015 – Ephemeris – The Harvest Moon effect
Ephemeris for Monday, September 28th. The Sun will rise at 7:36. It’ll be up for 11 hours and 52 minutes, setting at 7:29. The Moon, 1 day past full, will rise at 8:00 this evening.
Yesterday’s full moon was the famous Harvest Moon, the nearest full moon to the autumnal equinox. This is a time of the full and waning gibbous moons in the next few days rising in twilight. In the old days before electric lights it helped farmers by effectively lengthening the hours of light to gather in the crops. The Moon on average rises 50 minutes later each night. The interval between tonight’s moon rise and tomorrow’s will be 38 minutes. The interval between Tuesday and Wednesday will be 42 minutes. This year’s harvest moon effect is spoiled a bit because the Moon was at perigee Sunday, the so-called supermoon, so it’s moving faster in its orbit than average. Like the Sun, the Moon always appears orange or red near the horizon.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The positions of the Moon from September 28 to October 1, 2015. Note the path of the Moon. At Harvest Moon in northern Michigan time it makes less than a 45 degree angle with the horizon. For other latitudes it’s less than (90 – latitude). shorthand term for 90 – latitude is co-latitude. Created using Cartes du Ciel.
The closer to horizontal the Moon’s path is the shorter the difference in night-to-night rise times.
Bob Moler's Ephemeris Blog 