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01/30/2018 – Ephemeris – Looking for tomorrow’s lunar eclipse

January 30, 2018 2 comments

Ephemeris for Tuesday, January 30th. The Sun will rise at 8:04. It’ll be up for 9 hours and 44 minutes, setting at 5:48. The Moon, 1 day before full, will set at 8:04 tomorrow morning.

At a bit before 5 this morning the Moon passed perigee, it closest approach to the Earth in its monthly orbit of the Earth. It was 223,072 miles (359,000 km) away. That makes tonight’s Moon, 12 hours or less before full, a super moon. It will rise tonight at about 5:01. However it’s setting that is of interest because it will be in eclipse. The partial phase of tomorrow morning’s lunar eclipse will begin at 6:48 a.m. (11:48 UT), when the upper left part of the Moon will enter the Earth’s inner shadow, called the umbra. The Moon will be fully immersed in the shadow beginning at 7:51 a.m. (12:51 UT). It will probably disappear by then because the Sun will rise just after 8 a.m. and the Moon will set, at least in the Interlochen/Traverse City area at, 8:04.

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

Addendum

Partial eclipsed Moon

The partially eclipsed Moon in twilight at 7:40 a.m. January 31, 2018 from Traverse City, MI as simulated by Stellarium.

The following is an article I submitted to Green Elk Rapids website that was also published in the Elk Rapids News.  Elk Rapids is a village about 20 miles north of Traverse City on the east shore of Grand Traverse Bay.  I added the metric units for this post.

We will have a calendrical coincidence on January 31st along with a natural event, and just missing another natural event all having to do with the Moon. The first is that the full moon on January fits one of the definitions for a “blue moon”, the second full moon in a month. Of course the Moon doesn’t actually turn blue. It doesn’t really care. Since February is shorter than a lunation, a lunar month, it will not have a full moon. However March will have two full moons like January.

The second is a real event. The Moon being opposite the Sun in the sky, the definition of a full moon, will pass into the Earth’s shadow causing a lunar eclipse or eclipse of the Moon. In this case, a total eclipse. A lunar eclipse of some type occurs in about one in six full moons. We only have to be on the night side of the Earth to see it. That’s the rub this time, because the eclipse will be in progress at sunrise. The partial phase starts at 6:48 a.m. From about 6:30 on the upper left part of the Moon will appear dusky as the Moon sinks deeper in the Earth’s outer shadow, where the Sun is only partially blocked. The Moon will sink farther and farther into the Earth’s inner shadow called the umbra until at 7:51 a.m. it will be totally immersed. By then the sky will be quite bright, with sunrise to occur at 8:02. The Moon should completely disappear and will set unseen at 8:04. Folks a few states west of us will see, more than likely, a coppery colored totally eclipsed Moon. Some TV preacher some years ago called it a blood moon, hoping to sell books about the end times.*

The color comes from the sum of all the sunrise and sunsets happening on Earth at that instant. The red sunrise we see is caused by the blue light being scattered out of the Sun’s light by molecules in the Earth’s atmosphere. It gives us the blue sky. Our atmosphere also bends the Sun’s light. When we see the full disc of the Sun just clear the horizon, it’s still actually fully below the horizon. The light of the sunrise that passes over our heads continues on, being bent further and becoming redder, and fills the Earth’s shadow by the time it reaches the Moon’s distance, making the Moon red. Volcanic ash in the upper atmosphere can make the Moon almost disappear during totality.

This full moon is also a so-called “super moon”. These occur when the full moon is nearest the Earth in its monthly orbit of the Earth. January first’s full moon was the closest of the year, you might say a super-duper moon. The Moon reached its perigee, closest point or 221,581 miles (356,600 km) away 5 hours before the Moon was officially full. This time perigee is the day before full, about 1,500 miles (2,400 km) farther away. These are measured center to center. The closest an Elk Rapids observer will be to the Moon on the 31st will be at about 12:30 a.m. at 219,920 miles (353,927 km), subtracting most of the Earth’s radius. Of course the Moon won’t look that big being high in the south then. By moon set it will retreat to 223,778 miles (360,136 km) from an Elk Rapids observer. The increased apparent size of the rising or setting Sun or Moon is an optical illusion. The Moon is closer to us when high in the sky than when on the horizon.

The next lunar eclipse visible to us is next year, on the night of January 20-21, 2019.

* The Elk Rapids News didn’t like my dig about the TV preacher and omitted this sentence.  I rather expected them to.


Lunar Eclipse January 31, 2018

Credit NASA.

The original page for this graphic is:  https://eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2018Jan31T.pdf

    Total Lunar Eclipse January 31
Event               Time EST   Time UT
                    GT Area    
Enter penumbra      5:51 a.m.  10:51   Unseen
Begin partial phase 6:48 a.m.  11:48
Totality begins     7:51 a.m.  12:51
Sun rises           8:02 a.m.
Moon sets           8:04 a.m.
Mid eclipse                    13:28
Totality ends                  14:07
End partial phase              15:11
Leave penumbra                 16:08   Unseen

The shading of the penumbra is generally noticeable within 1/2
hour before the partial phase begins and again after it ends.

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04/14/2014 – Ephemeris – Why does Easter occur on a different Sunday every year?

April 14, 2017 Comments off

The answer is astronomical!

Ephemeris for Good Friday, Friday, April 14th.  The Sun will rise at 6:59.  It’ll be up for 13 hours and 26 minutes, setting at 8:26.  The Moon, 3 days past full, will rise at 11:48 this evening.

Easter will be celebrated by western and eastern christian churches this Sunday.  Easter is a movable feast in that it falls on a different date each year following the first full moon of spring.  It’s an attempt to follow the Jewish Passover, which starts on the 15th of the month of Nisan.  Being a lunar calendar the 15th the generally the night of the full moon.  And since the Last Supper was a Seder, the Christian church wanted to follow Passover as closely as possible using the Roman solar based calendar where the year was 365.25 days long.  Passover started at sunset this past Monday night.  The western churches eventually adopted the Gregorian calendar to keep in sync with the seasons.  The Eastern churches did not, however Easter is late enough this year so they both fall on the same date.

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

Addendum

The seasonal, or officially the Tropical Year, from vernal equinox to vernal equinox is approximately 365.24220 days long, about 11 1/2 minutes shorter than the Julian (after Julius Caesar) Calendar year.  The Julian Calendar kept up with the year by having three 365 ordinary years and one leap year of 366 days.  It over corrects.  To make the calculation for Easter easier in the various dioceses of the far-flung church, the vernal equinox, the day the Sun crosses the celestial equator, heading northward was defined as March 21st.  The actual vernal equinox was falling behind the Julian Calendar by 0.8 days every century.

By 1582 the Roman Catholic Church under Pope Gregory XIII decided to correct the problem.  By then the real vernal equinox occurred on March 11th.  Easter is supposed to be a spring feast, and using March 21st as the vernal equinox would eventually push Easter into summer.  The Pope instituted a commission to look into the problem.  This commission headed by Christophorus Clavius* came up with what we know as the Gregorian Calendar.  First, eliminate 10 days from the calendar.  This was done in October 1582 between October 4th and 15th.  Then to keep the calendar in sync with the actual year it was decreed that leap years would continued for years divisible by 4; except that century years, those divisible by 100 be ordinary years, except those by also divisible by 400.  Thus the year 1900 was an ordinary year, but the year 2000 was a leap year, and the year 2100 will be an ordinary year.  Adoption of this as a civil calendar took 400 years to be universal.

The Greek Orthodox and other eastern churches kept the Julian Calendar, so on occasion their Easter is sometimes celebrated in May.  The Jewish Calendar is, as I alluded to in the program transcript, a lunar calendar.  It has a relationship to the Julian Calendar in that 19 Julian Years equals 235 lunar months almost exactly. This is called the Metonic Cycle.  Those 235 months equal 12 lunar years of 12 and 13 months.  So without correction Passover too will slowly head into summer in millennia to come.

* Clavius was honored by having a large, rather spectacular crater on the Moon named for him.  Search these posts for Clavius to find it.

 

 

 

08/18/2016 – Ephemeris – Viewing the full Moon tonight

August 18, 2016 Comments off

Ephemeris for Thursday, August 18th.  The Sun rises at 6:49.  It’ll be up for 13 hours and 53 minutes, setting at 8:42.  The Moon, at full today, will rise at 8:54 this evening.

The full moon, contrary to what you’d think is a poor time to observe it.  The moon is essentially gray on gray.  And at full moon we are looking at the moon from about the same perspective as the sun, so there are no shadows to delineate its fine features.   Since the actual instant of full moon occurred at 5:27 this morning, some shadows will be creeping in on the moon’s upper right face as it is seen in the evening.  Full moon is the best time to see the maria or lunar seas, the dark areas that make up the man in the moon.  In binoculars can be seen the bright rays* emanating from the crater Tycho near the south end of the moon.  Other craters have rays too, but none so long and distinctive. Night by night for the next two weeks the moon’s illuminated landscape will wane.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

* Rays are caused by the ejecta from the impact that created the crater.  They are thought to be small craters themselves which show up best at full moon because they have no shadows in them.

Addendum

High contrast full Moow

The full Moon taken last night, 7 hours before to was officially full. The contrast was greatly enhanced to bring out Tycho’s ray system. Credit Bob Moler.

10/27/2015 – Ephemeris – Hunter’s Moon

October 27, 2015 Comments off

Ephemeris for Tuesday, October 27th.  The Sun will rise at 8:13.  It’ll be up for 10 hours and 25 minutes, setting at 6:39.   The Moon, at full today, will rise at 7:09 this evening.

Tonight’s full moon is known as the Hunter’s Moon because it is the full moon after the harvest moon.   The minute the Moon will be full will be at 7:05 this morning, about an hour before it sets. This was the time Native Americans and Europeans went out to secure the meat for the winter.  And it also coincides with the time of year of our hunting seasons.  So in that regard it fits nicely.  The names of the full moons throughout the year generally mesh with the activities or weather conditions of that month.  For instance December’s full moon is the Cold Moon or the Long Nights Moon.  December has the longest nights.  This list is taken from  farmersalmanac.com, the website of the Old Framers Almanac, from which I’ve been getting folklore  tidbits for years.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Other sources for full moon names: