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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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