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02/02/2019 – Ephemeris Extra – Groundhog Day and other seasonal days

February 2, 2019 Comments off

Note:  I wrote this article as part of the Grand Traverse Astronomical Society’s Stellar Sentinel for February 2019.

Groundhog day coming this month got me to thinking about the seasons and those special seasonal days, like solstices, equinoxes and cross-quarter days. February 2nd is a cross-quarter day, supposedly when winter is half over. Below is a table I created of the seasons for one year starting with last December’s winter solstice.

I took the date and times from Astronomical Tables of the Sun, Moon and Planets, Third edition by Jean Meeus. TD is Dynamical Time, used to calculate the positions of bodies in the solar system, is about 68 seconds fast compared to Universal Time (UT), which is tied to the Earth’s rotation. The difference is slowly changing at less than a second a year and doesn’t enter into the calculations. The Julian Date is a consecutive date starting on January 1, 4713 BC at noon UT. It’s used by astronomers to calculate date differences. like the length column in the table above without worrying how many days months have or how many leap years are in the interval. If you want to convert a calendar date to a Julian date or a Julian date to calendar date go to the Naval Observatory web page here: https://aa.usno.navy.mil/data/docs/JulianDate.php.

Note that the seasons are of different lengths. This is because the Earth’s orbit is slightly elliptical. It reached perihelion, its closest to the Sun, this year on January 3rd, and it will reach aphelion, its farthest, on July 4th. The Earth or any planet moves fastest when near perihelion. And with perihelion 14 days into winter, makes winter the shortest season. Autumn is the second shortest season 90 days compared to winter’s 89 days. Summer at nearly 94 day’s length is 4.7 days longer than winter. However we’re too far north to really notice it. Spring is second with nearly a 93 day length.

The rest of this article is based quite a bit on the web page: Common Holidays in Relation to Equinoxes, Solstices & Cross-Quarter Days – https://www.naic.edu/~gibson/cal/. It’s a cool list. Naic.edu is the website of the Arecibo Observatory in Puerto Rico. Apparently it was someone’s (Gibson’s) personal post.

The equinoxes and solstices are quarter days, for the four seasonal quarters of the year. The table above has Mid-Season and Date for the half way point in the season. The Cross-Quarter Days column are the dates which are more or less celebrated down throughout history.

The first celebrated cross-quarter day is February 2nd, Groundhog Day Which the famous weather prognosticating rodent in Punxsutawney, PA forecasts the length of winter based on if he sees his shadow. Supposedly, if he sees his shadow winter will last for six more weeks, if he doesn’t then spring is just around the corner. Actually from February second to the vernal equinox is six and a half weeks. If we had a winter like last year with a snowy April, winter lasted until the second cross-quarter day. The actual first cross-quarter day this year is February 4th. February 2nd, 40 days after Christmas, is also celebrated as Candlemas Day, when candles are blessed for the year, and the Feasts of the Purification of the Virgin Mary and The Presentation of the Child Jesus by the Catholic and some other Christian Churches.

The first quarter day is the vernal equinox, which occurs in our time zone on March 20th. The Ides of March, the 15th is pretty close to the vernal equinox and was the start of the year for a time with the Romans. It was the date in 44 BC that Julius Caesar was assassinated. March, named after the god Mars was also for a long time the first month of the year. They, for a time had 10 months, and consigned the winter months to ?. Later they added two months in front of March, which is why our 9th through 12th months are named September (7), October (8), November (9) and December (10).

The second cross-quarter day to be celebrated is May 1st, May Day. The actual 2nd cross-quarter day this year is May 6th.

The second quarter day, the summer solstice is on June 21st. It’s near midsummer day, the 24th, the feast of St. John the Baptist. It’s a big deal in Europe. If you had a midsummer’s night dream it would be on the night of June 23-24. Of course if that date was really midsummer, summer would have to start in early May.

The third cross-quarter day is August 1st, Lughnasadh. This is Celtic. It was the wedding day of Lugh, their sun god with the goddess of the Earth. This causes the crops to ripen in time to harvest in the fall. The actual date this year is August 7th.

The third quarter day is the autumnal equinox. This year it’s on September 23rd.

The fourth cross-quarter day is celebrated on October 31st, Halloween. It is the day before All Saints Day, and Day of the Dead in Mexico. The actual cross-quarter day this year is November 7th.

The fourth quarter day is the winter solstice, December 21st. This is in the midst of festivals ancient and modern around the time the Sun starts heading north again. Festivals of light, like Saturnalia, Yule, Christmas, and Hanukkah

There you have the days of our seasons.

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Categories: Ephemeris Extra, Seasons

01/20/2019 – Ephemeris lunar Eclipse extra

January 20, 2019 Comments off

For those of us who may be socked in tonight we have a link to the livestream of the eclipse.

This is the link:  https://livestream.com/GriffithObservatoryTV/LunarEclipseJanuary2019?origin=event_published&mixpanel_id=f1e6c5e68dbb0-067054b61-43681f0a-2ee000-f1e6c5e68ec0e&acc_id=7596023&medium=email

I subscribe to their email notices, which explains the end of the URL.

You can go to their main site: http://griffithobservatory.org/ and scroll down to Upcoming Activities and Total Lunar Eclipse then Watch live online.  That connection is real slow now.

Update 9:p.m. EST:

Looks like they are having clouds over LA.  However we (Interlochen/Traverse City, MI) are partly cloudy with more clear spots than clouds, and the clouds seem to be thin.  The GOES satellite is showing a thin lake effect flow from the north.  So maybe we might pull this one off.

GOES Great Lakes cloud animation

GOES Great Lakes cloud animation for 9 p.m. Credit NOAA.

12/15/2018 – Ephemeris Extra – Finally the skies cleared and I got a photograph of Comet Wirtanen

December 15, 2018 Comments off
Comet Wirtanen and the Pleiades

Comet 46P/Wirtanen and the Pleiades. 9:24 p.m. EST, December 14, 2018. Canon EOS Rebel T5, f/5.5, 30 sec., ISO-3200, fl 55mm, tracking.  Click on the image to enlarge.  Credit Bob Moler.

Finally, the skies cleared.  The last time we had clear skies was early in the evening on the 8th. Our family went to the Ballet that evening at Interlochen Center for the Arts, and by the time I got back and dressed to go outside and observe the comet, it had clouded up.  The Ballet was wonderful, by the way.

Anyway, Comet 46P/Wirtanen as a few hours ago was greatly hampered by the nearly first quarter Moon.  And it’s going to get worse as the moon’s phase gets fuller.  I thought I could see it in with the naked eye.  It was visible in binoculars.  As you can see it did photograph well.  I processed the image with GIMP to increase contrast, and reduce the background moonlight.  There is no discernible tail visually or in this photograph.  Longer exposures in a dark sky do show a faint ion tail.  Remember this is a short period comet, and has been around the Horn (perihelion) innumerable times.  It orbits the Sun from just inside Jupiter’s orbit to just outside Earth’s orbit every 5.4 years.

Happy comet hunting!

11/25/2018 – Ephemeris Extra – Comet 46P/Wirtanen may be naked eye in December

November 25, 2018 Comments off
Comet 46P/Wirtanen in December 2018
he path of Comet 46P/Wirtanen from November 21, 2018, to January 1, 2019. The labels are month, date, and expected magnitude. On November 22nd it was observed to be magnitude 5.5, about 5 magnitudes brighter than the predictions on the chart.  Click on image to enlarge. Created using Cartes du Ciel (Sky Charts).

Comet 46P/Wirtanen will be well placed in the evening sky for observation. Though a small comet, it has a history of being active, which is not disappointing us now. It will be closest to the Earth on December16th at 7.1 million miles (11.4 million km). 

On December 16th the comet will be closest to the Pleiades. On the 23rd it will appear close to the bright star Capella. After that it will become circumpolar.

Comet Wirtanen is a small short period comet of 5.44 years.  It’s orbit doesn’t come as close to the Sun as the Earth.  It’s closest to the Sun, called perihelion it which it reaches December 12th is about 98 million miles (158 million km).  The orbit extends out to nearly Jupiter’s orbit.

Checkout photos and animations of this and other comets in http://www.spaceweather.com/’s Realtime Comet Gallery.

Also check out Seiichi Yoshida’s website and his weekly information about Bright Comets: http://www.aerith.net/comet/weekly/current.html.

Comet and the Pleiades
Here is a black on white chart that I created for our society’s newsletter of the positions of the comet when it passes the Pleiades.  The positions are for 9 p.m. EST (01:00 UT on next date) on the displayed dates. Created with Cartes du Ciel (Sky Charts).

A note about comet magnitudes

Comet magnitudes are always devilishly hard to estimate. A comet always appears dimmer than its magnitude suggests because one is comparing the brightness of a diffuse object with the point source of a star. One either has to reduce the size of the comet to almost a point or defocus the star to the size of the comet to make the comparison if it doesn’t have a tail.

A point about magnitudes. They’re like golf scores. The lower the number, the brighter the object, and the better the golf score. Blame the ancient Greek astronomer Hipparchus, who ranked star brightness from first magnitude for the brightest stars to sixth magnitude for the dimmest stars visible to the naked eye. Modern astronomers put a mathematical basis for the system saying that a magnitude difference of 5 equals a brightness difference of 100. So each magnitude step equals the 5th root of 100 or 2.512. So a 5thmagnitude star is about two and a half times brighter than a 6thmagnitude star, and so on.

10/04/2018 – Ephemeris Extra – Wintermaker rising

November 4, 2018 Comments off

A chill is in the air, The Fisher, Ojiig’s bloody tail has swooped low in the north at midnight to paint the trees with their fall colors, and the leaves have fallen to the ground. Haven’t heard of the Fisher? I mention it from time to time here on my Ephemeris program on Interlochen Public Radio. It’s a constellation of the Anishinaabe peoples indigenous to this area of Michigan, of which the Chippewa, Ottawa, and Ojibwe are a part.

The Fisher occupies the stars which we know as the Big Dipper and the Great Bear, Ursa Major. And unlike the bear, a fisher really does have a long tail. The fisher is a real weasel-like animal whose diet apparently does not include fish. It is found across southern Canada and in the American West. I’ve related the story of the Fisher, and how he brought summer to the Earth, in these pages in the August 2012 issue and on my blog bobmoler.wordpress.com. Search for fisher. Like most legends, there are different versions of that story and others about the Fisher.
Fisher or not, summer is gone and the world seems darker and colder. Over in the east these evenings great winter constellation of Orion is rising. It brings to mind the Robert Frost poem Star-Splitter, and our star chart this month from the November 1st post:

“You know Orion always comes up sideways.
Throwing a leg up over our fence of mountains,
And rising on his hands, he looks in on me
Busy outdoors by lantern-light with something
I should have done by daylight, and indeed,
After the ground is frozen, I should have done
Before it froze, and a gust flings a handful
Of waste leaves at my smoky lantern chimney
To make fun of my way of doing things,
Or else fun of Orion's having caught me.
Has a man, I should like to ask, no rights
These forces are obliged to pay respect to?"

The rest of the poem is available on the Poetry Foundation website: https://www.poetryfoundation.org/poems/44273/the-star-splitter. The poem is about one Brad McLaughlin and his telescope. While I don’t approve of how he financed his telescope, I do share his enthusiasm.

North Hegman Lake Pictographs
North Hegman Lake Pictographs with the Wintermaker (Orion), Curly Tail (Leo-Hydra), and Moose (Pegasus). Credit: Etphonehome.

The Wintermaker, Biboonikeonini’s, name literally means North Wind. While his torso is the same as Orion’s his arms stretch from Aldebaran in Taurus to Procyon in Canis Minor, just about spanning the entire winter sky. The pictographs, seen above of the Wintermaker, Curly Tail and Moose can only be seen from a canoe in the cliff face on one side of the narrows between North Hegman and Trease lakes, 15 miles north of Ely, Minnesota


Wintermaker rising
The Wintermaker (Orion) rising in the east-southeast. And Hole-In-The-Sky (Pleiades) as seen in Stellarium with Ojibwe Star Lore in Stellarium. From the Ojibwe Sky Star Map Constellation Guide, ISBN 978-0-615-98678-4 by A. Lee, W. Wilson, and C. Gawboy.

In late winter as Ojiig is rising in the northeast signaling the maple sugaring season, the Wintermaker is moving lower in the southwest. Some Ojibwe parents make bows for their children to shoot arrows at the Wintermaker to convince him to flee the skies so spring can begin as a way to teach them the old legends of their culture.

The Pleiades is an important group of stars for the Anishinaabe in several ways. It is the Hole-In-The-Sky, Bagone’giizhig, through which the Sky Woman fell and to give birth to the first humans on the Earth.

The Pleiades also represent the seven poles of the Shaking Tent Ceremony, and the seven sacred stones that are heated for the sweat lodge, which is also seen in the stars in the spring as Corona Borealis.

They are also the Seven Daughters of the Moon and Sun. They loved to dance and play, and when their father, the Moon was low in the sky, would descend to the Earth in a basket to do their thing. On one of their trips to the earth, one of them was captured by a human and she ended up falling in love with him, and married him. When father Moon found out he permanently dimmed her star, so now most people now only can spot 6 of the stars. This last bit seems to parallel the Greek story of the lost Pleiad.

Note:  This is published as an article in the Grand Traverse Astronomical Society’s November 2018 newsletter Stellar Sentinel.


Ephemeris Extra – The great meteor shower of August

August 5, 2018 Comments off

This post from the Grand Traverse Astronomical Newsletter “Stellar Sentinel” was written for August of 2018. The dates and times of the peak may change a bit from year to year.

The Perseid meteor shower is the second most active annual meteor shower. The most active is the Geminids of December during a period that’s cold and generally very cloudy here in Northern Michigan. Consequently, I’ve never seen a Geminid meteor.

The Perseid meteor shower is the most famous as the August meteor shower, coming on the warm summer month. In Northern Michigan the radiant of the shower, the point in the sky from which they appear to come, is circumpolar, which means they are visible anytime in dark skies from dusk to dawn.

The Perseids are so named because they appear to come from near the constellation of Perseus the hero, an autumn constellation that starts the evening low in the northeast and rises and moves to high in the east near dawn. In earlier times these meteors were called the Tears of St. Lawrence, who was martyred in AD 255. His Feast day is August 10th, the day he died, which falls very close to the peak activity of the shower.

The Perseid meteors are visible for over a month from about July 17th to August 24th, with peak activity between August 12th at 4 p.m. to August 13th at 4 a.m. EDT. So the peak activity will partially be during our night hours, and the one day old Moon will not interfere at all. The peak hourly rate may reach 100 per hour at times. All things being equal, the higher the radiant is in the sky the greater the numbers of meteors seen. The Perseid radiant will be rising all night, being highest as the first light of dawn appears. Even though the numbers of meteors are fewer I like to start looking by 10:30 p.m. With the radiant low in the sky, the meteoroid particles we see are almost skimming the atmosphere, lasting longer. There’s is nothing so cool as to see a bright Perseid meteor seeming to fly along the Milky Way. The radiant point is in the Milky Way between Perseus below, and Cassiopeia above.

Perseid Radiant

The Perseid radiant is located off the highest star is Perseus as it rises about 11 p.m. August 12, 2018. Click on the image to enlarge. Created using Stellarium.

Observing this meteor shower is very easy and one needs no special equipment. A blanket to lie on, mosquito repellent, warm clothes, some water and snacks, if staying the night, and a dark location. My preferred location is the Dune Climb at the Sleeping Bear Dunes National Lakeshore. It has no light, except the occasional car lights and has modern restroom facilities and a low horizon except in the west. I supposed one could climb up the dune to get rid of even the car lights. Even though the radiant is in the northeast, the meteors will appear all over the sky.

Binoculars are nice to take a break to explore the Milky Way and to observe the smoky train left by a particularly bright meteor. These can be viewed for a minute of more and deform and twist due to the different wind directions and speeds at different altitudes.

What causes the Perseid meteor shower and why does it occur at the same time every year?

The Perseid meteor shower, like all meteor showers are caused by the debris left along the orbits of comets. If the comet’s orbit crosses close to the Earth’s orbit we can get a meteor shower. Comets spend the majority of their time far from the Sun, where it’s very cold, and are in very elongated orbits.

Comets are made from rocky bits, dust and frozen gasses. As the comet comes into the inner solar system the Sun heats it up and the frozen gasses sublimate, are ionized by the Sun’s radiation and are caught into the thin ion tail. This liberates the comet’s fine dust which is blown away from the Sun by the pressure of sunlight into a broad dust tail. Larger particles end up traveling in the comet’s path, and are affected mainly by the Sun and the various gravitational tugs of the planets.

The comet responsible for the Perseids is 109P/Swift-Tuttle. It was independently discovered by L. Swift and P. Tuttle in 1862. It was recorded as being seen in 69 BC by, you guessed it, the Chinese. It’s a big comet, with a nucleus some 16 miles in diameter, and it crosses the Earth’s orbit, so it is a potentially hazardous object, and if it hit the Earth, would wreak more damage than the asteroid that killed the dinosaurs. From the 1862 appearance the comet was given a period of 120 years. It didn’t show in 1982. An observation of the previous appearance of the comet in 1737 allowed a recalculation of the orbit and a new return year of 1992. That was correct. The comet was recovered that year.

The comet will return in 2126. The calculations used to predict the 1992 return suggested that the comet could possible collide with the Earth. However observations of the 1992 appearance of the comet determined that the comet, though it would pass close to the Earth, is not a hazard. But it should be really bright. I can’t wait!

Ephemeris Extra – Occultation of Aldebaran visible from the Upper Peninsula and the tip of northern lower Michigan

July 8, 2018 Comments off

In the early morning hours of July 10th the very northern part of the IPR listening area will have a chance to see the last occultation of the bright star Aldebaran for at last 15 years. An occultation is where the Moon in this case passes in front of or occults a planet or a star. In astronomy occult means to hide. The event is an occultation. There is no black magic involved. It will be a grazing event, with Aldebaran popping in and out of view at the mountains and valleys at the southern edge of the Moon along a line running south of Mackinaw City and across the eastern tip of the Upper Peninsula.

Occultation of Aldebaran map

The Straits of Mackinac area showing the green southern graze line of the Occultation of Aldebaran. Credit Map Google Earth, Graze line by Occult 4.

It’s a clear miss for the Interlochen area, with the star skirting the Moon at it’s 5 o’clock position. The time of the event will be near 4:38 a.m. with the maximum time of the event increasing from west to east at nearly 2,000 miles an hour. At that time the Moon and Aldebaran will be low in the east-northeast and only 7 degrees above the horizon.

Moon and Aldebaran finder chart

Location of the Moon and Aldebaran in the sky at 4:38 a.m. July 10, 2018 from the Interlochen/Traverse City area.

More information on this occultation from Sky and Telescope is here.
This will be the last occultation of Aldebaran visible from around here for the next 15 years. However starting in 5 years there will be a monthly series of occultations of the bright star Regulus, and the next year a series of occultations of the star Spica will begin. That’s just for the Moon with bright stars. The Moon occults many dimmer stars a month. A very important field of occultations is the observation of occultations of asteroids and Kuiper belt objects to discover their size, shape, any satellites and whether they have rings. Go to the International Occultation Timing Association https://occultations.org for more information.

Hat tip to Jerry Dobek, Director of the Joseph H. Rogers Observatory