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Wednesday, July 11, 2018

Century's Longest Lunar Eclipse July 27, Tu B'Av!

The century's longest lunar eclipse is on Friday night July 27, Tu B'Av on the Jewish calendar. And lucky you if you live in Israel because you will have one of the best front row seats. Those living in the Americas and Canada, sorry! The eclipse ends before moon rise in your part of the world. So grab your best guy or gal, get an airplane ticket, and celebrate the Jewish night of romance with them under the totally eclipsed moon in Israel.

The chart below shows the timings and circumstances of the eclipse:

Total lunar eclipse of July 27, 2018
Timings and circumstances of the total lunar eclipse of July 27, 2018

Timings  of  the total lunar eclipse for Israel, with local Israel Daylight Times in parenthesis. In other words, the lunar eclipse begins at 9:24PM local time on Friday night, July 27, peak darkness is at 11:22PM on July 27, and ends at 1:19AM the morning of July 28.

2018 July 27
Partial eclipse begins: 18:24  UTC ( 21:24 Israel Daylight Time)
Total eclipse begins: 19:30  UTC (22:30 Israel Daylight Time)
Greatest eclipse: 20:22 UTC (23:22 Israel Daylight Time) 
Total eclipse ends: 21:13  UTC (00:13 Israel Daylight Time)
Partial eclipse ends: 22:19 UTC (01:19 Israel Daylight Time)
This is such a long eclipse because as you will note from the chart above, the moon passes almost directly through the very center of the earth's shadow, its widest part, spending the longest time of the 21st century in eclipse! This is also a Micromoon full moon, the opposite of a Supermoon. A Micromoon full moon occurs when the full moon is at apogee, its greatest distance from the earth, so it appears smaller in the sky. Hence it also spends more time in the earth's shadow. Aren't we lucky to be alive on this date and living in Israel for a front row seat!

Take some time while watching the eclipse to note the moon's darkness, called its Danjon Number during an eclipse. 0 is darkest, 5 is brightest. When the moon passes centrally through the  earth's shadow it's farthest from the edges of the shadow, so less sunlight gets refracted onto its surface during the eclipse.  During some very dark eclipses the moon may completely disappear. But this also depends alot on the earth's atmosphere at the time. The denser or cloudier it is around the globe the more sunlight gets refracted onto the moon and the brighter the eclipse. This is hard to predict so it should be fun to look for how dark this eclipse is and estimate its Danjon number. You can find out more about the Danjon Scale here.

All lunar eclipses occur during full moon, when the moon is opposite the sun with the earth in between. July 27th's eclipse falls out on the full moon of the Jewish month of Av, or Tu (meaning 15) B'Av, often referred to as Jewish Valentine's Day, since on this day in ancient times the girls used to dress in their finest and dance in the fields to encourage matches with the boys. A happy time after the fast and mourning of the 9th of Av, Tisha B'Av. So, what could be better than going out with your Bestie to enjoy the romance of the longest lunar eclipse of the 21st century? I will leave it to the astrologers if this is a good or bad omen, the eclipse of the light of love or its revelation in the darkness of the moon. In any case this should not be one of those famous "blood red" moon eclipses since it is so central in the earth's shadow and little refracted sunlight, which causes the red color, should be evident. In any case be sure to take in all the planets that will be visible during the night, and especially during the darkness of totality. (See our previous post on the summer planets.)

You need no optical aid to the view a lunar eclipse but even small binoculars enhance the view and will show you details on the moon that are otherwise invisible to the naked eye.

There are many events being held to view the lunar eclipse in Mitzpe Ramon, but since this is a Shabbat night we will not be holding our usual star tour. You can look those events up online  if you want to come down here. But a full moon and eclipse is usually so bright that you should be able to watch it from almost anywhere in Israel from the beaches of the Mediterranean to Diezengoff Square.
When I complained to a friend  that the longest lunar eclipse of the century was falling on Shabbat and I wouldn't be able to hold a star tour, he told me, "Relax, it's Gd's way of telling you to just enjoy yourself for once." And so I shall. I hope you do,too!

To find out more about this eclipse see here.


Friday, July 6, 2018

2018: Best Summer I can Remember for Viewing Naked Eye Planets

This is the best summer  I can remember ever for viewing the naked eye planets. All five, Mercury, Venus, Mars, Jupiter, and Saturn, are all visible in the early evening sky, sometimes as many as four at one time! These are all the planets known to  the ancients, the sixth, Uranus, not being visible to the naked eye had to await the invention of the telescope and was discovered by the famous British astronomer Sir William Herschel on March 13, 1781.

Start off your evening of planet watching at 8:30pm looking west. You can't help but see the brilliant luminary Venus high in the western sky, looking like a beacon of light. In fact during war times it has frequently been mistaken as an incoming enemy aircraft and shot at by anti-aircraft gunners. They missed. Below and to the right of Venus, about 2/3rds down a diagonal line connecting Venus to the sunset point, is much dimmer Mercury. Around 8:30pm on July 6-12 it is the only other bright object visible in the sky, about 15 degrees above the horizon, WNW. Can you see it's distinctly yellow color compared to creamy white Venus?

Venus and Mercury in the western sky about 8:30pm on July 6, 2018.
Later in mid-July the new moon will appear near Mercury and make it easier to find if you haven't found it yet.

Venus and Mercury during mid-July with the new crescent moon right next to Mercury.
Don't wait too long to look for elusive Mercury it will start sinking lower in the sky at dusk after mid-month as it heads back towards the sun. This is a particularly good apparition of the planet with it so high in the sky and making it so easily found.

While you're watching Mercury set turn Eastward to find the ringed gas-giant planet Saturn rising about 15 degrees above the horizon in the southeast, right above the bow of the constellation Sagittarius. While the dimmest of all the planets in the sky now, besides Mercury, it is still the distinctively brightest object in that region of the sky. It kind of distorts the shape of the Archer's bow as it lies just above and left of its top-most star.

Now turn and face due south. It's hard to miss the brightest object now high in the sky at about 50 degrees above the horizon, the brilliant gas-giant Jupiter. After Venus sets about 10:00pm it is distinctively the brightest object in the sky.

You have now seen four of the five naked eye planets simultaneously in the  sky, a rare occurrence. I can't remember the last time I saw so many.

But wait! It get's better. Around 10:15pm be sure to look due east where you will see the brilliant red planet Mars rise at the horizon. This is the best apparition of Mars since 2003, so it is a brilliant red orb in the sky, brighter even than Jupiter, another rare occurence. Be sure to watch it as it rises and see if you can feel the earth move beneath you. I never can!

You have now seen all five naked eye planets in the sky in the span of just two hours. I have no idea when this will happen again so enjoy it now while you can.

For a real thrill why not join us for a star tour in Mitzpe Ramon where you can see the planets through our telescopes, as well as the star clouds of the Milky Way with the ringed planet Saturn in the foreground. Click the link below for a reservation.

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Friday, April 20, 2018

Lyrid Meteor Shower Peaks this Saturday Night and Sunday Morning, April 21-22

If you stay up to watch past midnight on the morning of April 22, the crescent moon will have set, the radiant will be high in the sky and you should see a good display of meteors. The peak number of meteors per hour tends to run 10-20 in a moonless sky, not a huge number but certainly worth looking for.

http://www.skyandtelescope.com/observing/lyrid-shower-kicks-off-year-of-great-meteor-watching/#.Wtm5pTJN0wI.facebook


A Lyrid meteor streaks through the sky as captured by Simon Waldram.


Tuesday, March 20, 2018

Welcome to Spring, March 20, 6:15pm IST

Astronomy Israel welcomes you to the official beginning of Spring which occurs at 6:15pm Israel Standard Time on March 20, 2018. This is astronomically called the Vernal Equinox, Vernal meaning "spring" in Latin, Equinox, meaning "equal night" in Latin, as on this day daylight hours and night time hours become equal. From this day forward the days start to get longer and the nights shorter. The earth stands with its axis perpendicular to the plane of its orbit around the sun.


At the Vernal Equinox the earth's axs stands perpendicular to ts orbit around the sun. Day and night are equal. It is the official astronomical beginning of Spring. And welcome to it!

Don't Miss Venus, Mercury and the New Moon, March 20-25

This update comes a bit late, as I have lost track of the planets for a while, but the end of March has the best display of the planet Venus and the elusive planet Mercury, together with a beautiful crescent moon, in a long time. look west, toward the sunset point, starting around 6:00PM between March 20-25  to see bright, beautiful Venus in the western sky, just below a waxing crescent moon. Just to the right and a bit above Venus is much dimmer Mercury. It will be harder to see as the sky is still bright from the setting sun, and it  is nowhere near as bright as Venus, but it is visible as the sky gets darker with the naked eye. Binoculars will show Mercury easily in the same field of view as Venus. Be sure to catch this beautiful tableau at the end of March. By March 25 Venus and Mercury will be farther apart and Mercury will be more difficult to see, but Venus will remain a shining beacon in the western sky a sunset, worth looking for throughout Spring.

Because Mercury is never far from the sun it is always hard to spot so any occassion where it appears high in a relatively dark sky is an opportunity to see our elusive closest planet to the sun. And remember, Mercury is so elusive that Copernicus himself was rumored to never have observed it with his own  eyes. So, go out at sunset, look west, and enjoy the spectacle of our nearest planets, Mercury and Venus, in the sky close to our nearest celestial body, the earth's own moon!


Venus, elusive Mercury, and the new moon in the western sky at sunset. Don't miss the spectacle March 20-25, 2018!
Update on March 22, 2018:
Mercury has now moved to the lower right of Venus, no longer above it. Hold your hand out at arm's length and put up three fingers. Mercury now lies three fingers to the right of Venus and just below it in the sky. I was not able to see it with my naked eye from a light polluted park in Mitzpe Ramon, but it should be quite evident with almost any pair of binoculars. once you've identified its location in binoculars you can make it out as a pin prick of light, even in heavy light pollution. Good luck!


Wednesday, January 31, 2018

A Very Special Tu B'Shevat on January 31, 2018

Tu B'Shevat is known as the "Birthday of the Trees". The name is simply the Hebrew date, the 15th of the month of Shevat, which usually falls in late January or early February. It is the date from which the age of trees is counted for purposes of taking tithes during Temple times or the age of a tree of purposes off eating its fruit. The Torah forbids eating the fruit of a tree until it is 4 years old ("Orlah"). How do we know how old a tree is? We start counting from Tu B'Shevat. That's why it's called the "Birthday of Trees". So, for halachic purposes, a tree planed one day before Tu B'Shevat becomes 1 year old on that day. And another year old on each successive Tu B'Shevat.

This year's TuB'Shevat is extra special because it corresponds to the triple astronomical whamy of a Super-Blue-Blood-Moon. (http://www.astronomyisrael.com/2018/01/super-blue-blood-moon-on-january-31-2018.html) The last time this triple astronomical whamy happened was in 1866. I have no idea when it also last coincided with TuB'Shevat!

But you may be asking yourself why TuB'shevat was picked for the birthday of the trees. Why not another date? And the answer, perhaps not surprisingly, is astronomical. TuB'Shevat is the birthday of the trees because it is a lunar, cross-quarter day. That is, it marks the cross over the middle of the winter quarter. It is half-way between the winter solstice on December 21 and the Spring equinox of March 20. So, half the winter is behind us on this day, and we start looking forward to the coming of spring. And because of this, in the temperate climate of Israel, and other similar climates, the trees beging to set their first flowers. Of course,  the Jewish  calendar being a lunar calendar, this is marked by a lunar event, the full moon of Shevat, which occurs on the 15th of the month, hence the Hebrew letters tet-vav (pronounced tu [two]), whose numerical value is 15. That TuB'shevat falls this year on a Super-Blue-Blood-Moon night is extra special. In fact TuB'shevat ends this year as the supermoon rises over Israel at 5:18PM in Jerusalem. I'm sure those versed in Kabbalh, Zohar, Chasidus, and astrology can tell you exactly what this means in each of those traditions, although I cannot.

Many folk cultures celebrate this cross-quarter day, but in the solar calendar, not the lunar calendar. Do you know what day that is? That's right - it's Groundhog Day (February 2) in the United States. That's the day Puxtahawney Phil emerges from his burrow and lets the world know if winter is over or if there will be another 6 weeks of winter. Why 6 weeks? Because it's half of 12 weeks (or half the winter season behind, half ahead), with just another 6 weeks to go until the Spring Equinox. It's the solar cross quarter day. It derives from the German Candelmas Day, which like many Christian traditions, derives from the Jewish TuB'Shevat.

So, the next time Groundhog Day rolls around, just remember it's the way the rest of the world celebrates TuB'shevat.









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