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    My Journey through the Astronomical Year

    Think of this as a "companion text" to this, the main web site. Not required reading, butI hope you'll find it interesting and helpful.

Events December 2010: Eclipse of the Moon, Great Geminid meteors, and planets at all hours!

Lunar Eclipse Update – December 21, 2010 – 11 am EST – I fear much of the lunar eclipse reporting  – and photos –  doesn’t capture the real wonder  of what is going on – the up-the-down-escalator motion of the Moon through Earth’s shadow.

My friends Dom and Daphne from Australia, who were here observing with us in October, had a very special view of the eclipsed Moon, that does drive this home and have created a wonderful, online slideshow so we can see what they saw.  The for their view is the Moon was just emerging from totality as it rose in their eastern sky at sunset.  What make their report  special is the nearness to the eastern horizon of the Moon and the  proximity of all this to sunset so that the Earth’s shadow is actually tangible to us, along with the Belt of Venus, in the Eastern sky.

So take special note of the first shot that looks east where the shadow and the belt of Venus are.  Then watch as the Moon drops out of that shadow, diving towards the ocean – the eastern horizon. Also note the curvature of the Earth’s shadow on the moon – something that told the Greeks, long before Columbus, that the Earth was round.

What this drives home for me is that we  are seeing the shadow of the Earth darken the skynear the horizon to the east, as we always do right after sunset and – since we’re on the Earth – that shadow is huge from our perspective. Yet, out in the vicinity  of the Moon the shadow is only about 6,000 miles in diameter. At that distance, 6,000 miles would cover about a degree and a half of our sky – just three times the apparent diameter of the Moon – and so we see  the Moon appear to drop down out of that shadow – that is the Moon is moving eastward towards the horizon, while the whole show – Earth’s shadow and the Moon appear to be moving westward as the Earth turns.

Simply wonderful!  we all know the textvook explanation, but nothing beats seeing it live and the next best thing is to get a fine report of it such as the slide show Daphne put together – enjoy!

http://www.bondiblue.net/lunareclipse/eclipse.htm

 

Lunar Eclipse Update – December 21, 2010 – 7 am EST Lot’s of reports with splendid photos of the eclipse showing a very red Moon as happens when our upper atmosphere is clear can be found on today’s Spaceweather.com. Go there and explore.  Although I love to observe without aid of cameras and computers, I also loved this report and photos from Bill Williams, an amateur in Florida. Bill wrote:

“I robotically controlled my telescope (14.5-inch RCOS) and camera (Apogee U16M) remotely 307 miles away at the Chiefland Astronomy Village using the internet. I transferred the data back to Boca Raton and processed it. Is this a great hobby or what?!”

To see his pictures go here.

Lunar Eclipse Update – December 21, 2010 – 3 am EST – Bt was cloudy here in Westport, MA, but there were several Web cameras available from various locations, though most of the ones I checked were being overwhelmed by the number of people looking for a live feed showing the eclipse.

I did find the one pictured below and although it sometimes stood still, it really did give a sense of being there. Here are some screen shots of the “live” action I could see.  I should note, that while we had light snow all day, and the sky was totally overcast, before the eclipse both the sky and the night in general were very light. The full Moon shone through the clouds and bounced off the fresh snow.  By totality, however,  it was very dark – not because of heavier clouds, of course, but because the Moon wasn’t shining through the high thin overcast any more. Very dramatic change I hadn’t anticipated. Here are the screen captures of one web cast.

Click on image for larger view. In the last image of Moon the folks web casting this had changed their camera settings so it was more sensitive to the light of the eclipsed Moon.

Orrinal post on December events follows:

It’s been three years since North America was treated to a total eclipse of the Moon – and it will be more than three years until we get another chance like this! That’s a long time between lunar eclipses, so let’s put clear weather on our holiday wish list for the night of December 20/21 when there will be a terrific total eclipse!

And that’s not all – with the right weather December could be a classic month for sleep deprivation with two great early morning events, plus other cool stuff happening at more reasonable hours, so this post is divided into three parts:

Best lunar eclipse in years! December 20/21, 2010

Click image for larger view.

Yep, you folks on the East Coast are reading that correctly – this is a morning event for us, but before you write it off, read on. I have a “half-is-much-more- than-50-per-cent” eclipse plan that you might want to try. The West Coast gets a break – an eclipse of the Moon happens at the same instant for everyone, but since we live in different time zones that instant occurs at different local times. So for the West Coast, the Moon turns into the Great Pumpkin just before midnight Pacific Standard Time. Oh – and if you’re on the East Coast of Australia – say Sydney? Well, you don’t miss out entirely. You get treated to the rather eerie spectacle of the Moon rising while already totally eclipsed. That will mean your first eclipse challenge will be to find the Moon! And all of this takes place in the most fabulous section of sky imaginable – right in the middle of some of the brightest constellations – Orion, Gemini, Taurus, and friends. And of course, these will be washed out by the full Moon prior to the eclipse, but during the eclipse they’ll come out in their full glory and the darkened Moon will occult a star or two as it journeys eastward. What a show! Study the map below to see if the eclipse is visible form your section of the world.

Click on image for a larger view.

And here is the eclipse sequence in Greenwich Mean Time so you can figure out how that relates to your time zone.

Click on image for larger view.

All these wonderful graphics are courtesy of Fred Espenak, www.MrEclipse.com) / CC BY-NC-ND 3.0 who has a terrific eclipse web site with lots of details about this eclipse and eclipses in general.

My half-is-much-more-than-50-per-cent plan

The real fun of an eclipse is in seeing the cover up – or uncovering – while at the same time watching the changing sky. I’m for seeing the whole show and if the weather gods cooperate, I plan to. But, I’m retired and seldom sleep more than four hours at a time, so mornings are no problem for me. Others have jobs to do and need their sleep. If that were my situation, I would try to carve out two hours and dedicate them to eclipse watching. That way I could get a real sense of the eclipse, while minimizing sleep loss. I figure if you see half of it, it’s almost as good as seeing the whole thing. So using the EST times I would make it a point to go out some time in the early evening for a few minutes just to appreciate the full Moon and note how it has washed out all but the brightest stars. Then I’d set my alarm for about 1:15 am and pop out to see the onset of the partial eclipse, which starts at 1:33 am. Again, note how the Moon is washing out most of the bright stars, even though it’s now fully into the penumbra – the weak part of the Earth’s shadow – and starting to enter the umbra. I’d stick it out to totality which begins at 2:41 am, take the next 20 minutes to enjoy the full glory of the stars with a totally eclipsed Moon, then be back to bed shortly after 3 am – thus losing about two hours sleep.

Of course you could work the same thing on the other side of the eclipse. Go to bed early and then get up about 3:15 am. If you’re out by 3:30 am, that will give you time to locate and appreciate the fully eclipsed Moon – note on the star charts below where it will be then – then watch it emerge from the Earth’s shadow starting at 3:53 am and over the next hour wash out more and more of the stars until totality ends at 5:01 am.

Or the-heck-with-sleep-plan, bring on the show!

Hey – one complete total eclipse in nearly six years – are you really going to let a little sleep deprivation steal the show? I’m not. This eclipse has me really psyched for several reasons. First, this is a real dry period between eclipses. There is one next June 15, but North America misses that one entirely. Next December (December 10, 2011) there’s another, and this one can be seen in part by those on the West Coast of North America. But the next full show for all of North America is not until April 14-15, 2014.

Another thing I like about this eclipse is it comes near the time of the winter solstice – 6:38pm, December 21,2010 – and that means the full Moon will be very high in our sky. The full Moon always rises opposite the Sun – so as the winter Sun sets in the southwest, the full Moon will rise in the northeast and travel high overhead.

A third thing I like is where, exactly, in the sky the Moon will be – it’s right in the middle of the Winter Hexagon – an area of sky that includes some of the brightest stars we see and most dramatic asterisms. In fact, the constellation that nearly everyone knows is Orion, and on eclipse night it’s going to look like Orion’s balancing the Moon on the end of his raised club! No kidding. Maybe we should think of that club as a torch for this night. Take a look!

Here's the Moon poised near the end of Orion's club just before the eclipse begins. Of course the Moon will drown out all but the brightest stars in Orion, but once totality begins most of these stars should be visible. (Starry Nights Pro screenshot.)

Is that cool? But wait, there’s more!

I admit I can’t spend hours looking at an eclipsed Moon – especially when there are so many other things to see in the surrounding sky. So by all means, bring your binoculars or a small telescope to this event. I’ll be using a telescope, but here I’ll stick to describing the naked eye and binocular sights.

Winter Hexagon and other things to look for as the moon gets darker and the stars come out. (Modified Starry Nights Pro screenshot.)

Click here for a printer-friendly version of the above chart.

The Winter Hexagon is a wonderful region of night sky, alive with a wide variety of sights. The stars that form it are among the brightest, starting with Sirius, the brightest star in the northern celestial hemisphere and at 8 light years, one of our closest companions. Procyon plays the “Little Dog” to the Sirius “Big Dog” – Sirius is the brightest star in Canis Major, Procyon the brightest star in Canis Minor. Castor and Pollux, the heavenly twins, anchor the next corner of the hexagon; then comes brilliant Capella, followed by the orange-tinted Aldebaran – the “bull’s eye” – and finally, the icy blue star at Orion’s left foot, Rigel. The best binocular sites in this area start with the Pleiades star cluster and its close neighbor, the Hyades cluster. (See the “look east” post for December for more about these two.) Orion’s Belt – the three bright stars in a row – slashes across the celestial equator and also is a wonderful, star-rich area to explore with binoculars. Finally, there’s the Great Orion Nebula – M42 – in the giant’s sword that hangs below his belt. Binoculars will show a little cloud in the middle of the sword that is an incredible region of gas and dust where stars are being born. Of course to see all this at its best you need to wait for totality at 2:41 am.

With binoculars or telescope

Obviously you can look at mountains, craters, and seas on the Moon and watch as they each get caught in the Earth’s shadow. But what I think will be most fun is to note the eastward motion of the moon by looking at its leading edge – the dark edge – and watch as one star after another gets snuffed out by the Moon. Now these stars will be more difficult to see during the partial phase, but the darker the moon gets, the easier it will be to see this happen and thus get a real sense that the Moon is indeed traveling around us. The Moon, like everything else in the sky, will appear to move from east to west. But at the same time, its motion around the Earth causes it to move eastward against the backdrop of distant stars. Once totally eclipsed, these “occultations” should be very easy to see.

The following video is a simulation made with Starry Nights Pro software. It shows the view from my location at 42 degrees north. Your view of the Moon – and which stars it occults – will depend on your latitude -so unless you’re within about 10 degrees of me either direction, you should take this simulation as illustrating what to expect in general, but the specific stars will differ. The brightest star occulted near the start is magnitude 7 HIP27698 – which should be visible in binoculars, if not at the start, certainly later when it pops out of the other side from behind a fully eclipsed Moon. The dimmest shown are about magnitude 12 and only visible in telescopes of the size most amateur astronomers use.

Oh – and if you stay up until the end of the eclipse, be sure to take a look at Saturn about 30 degrees high in the southeast and just five degrees from the beautiful double star Porrima. As always, it’s a grand show in any size telescope and now its rings are well displayed – the last couple of years they haven’t been. Below and to the left, Venus will be about six degrees above the eastern horizon and outshining everything except the Moon. Porrima, by the way, is an exquisite, but challenging double for small telescopes that’s getting a little easier to split every month as the two nearly identical stars move farther apart in their orbits.

A Geminids Storm! December 13/14 2010

This could be the best meteor shower of the year, especially for residents on the East Coast of North America – though it should be very good across the country.

The Geminids weren’t discovered until 1862, and when they were, they were more a meteor sprinkle, than a meteor shower. In 1877 astronomers were recording about 14 per hour. That’s wimpy. The Zenith Hourly Rate (ZHR) for the Perseids is 120. But a funny thing happened on the way to 2010 – the Geminids just kept getting better. In the 1930s the rate climbed to 50, was 60 per hour in the next two decades, and about 80 for the remainder of the century. But the respected “Observer’s Handbook 2010” of the Royal Astronomical Society of Canada puts the rate for this year at 120 – tied with the Perseids – and some say it could go higher!

Now before you get salivating to go out on a cold December night and lie in a lounge chair, let me set the record straight on “zenith hourly rate.” This is the number that’s usually quoted in various accounts – but most of the time this rate is mentioned it’s not explained and it leaves too many people with false hopes – especially those living in light-polluted areas, which is most of us. This rate is for ideal conditions, and I’ve never been lucky enough to have those ideal conditions. I would be tickled pink if I averaged one meteor per minute from a very dark site – the best I can do near home. Here’s how ZHR is defined in the Handbook:

Zenith Hourly Rate (ZHR) defined as the number of meteors a single average observer would see if the radiant were directly overhead and the sky dark and transparent with a limiting stellar magnitude of +6.5 (conditions that are rarely met in reality.)

That last phrase could also be written as “never in my lifetime!” 😉 I consider my skies super when the limiting magnitude is 5.5. Now I’m not a dedicated meteor shower watcher – but I’ve certainly been out there many nights over the years and generally have had very enjoyable meteor observing sessions – but seldom anything like what people report from the rare ideal site. But then – to have all the astronomical conditions just right is rare enough – yet that’s what this year’s Geminids could deliver, particularly for folks in the eastern half of the country. (As you move west there will be more interference from the Moon at the predicted shower peak time, but the Geminids still should put on a terrific display. The Moon will be low and just past first quarter.)

Oh – and for the radiant of this shower to be directly overhead here? The radiant – the general area where the meteors appear to radiate from – is a point less than two degrees from the bright star Castor and will be as high as it gets in my sky at 2:42 am EST. That won’t be directly overhead – but it’s at about 79 degrees altitude which is close enough to call directly overhead. (Use the Winter Hexagon chart posted above to find Castor – it’s the bright star near the top and is identified in that chart.)

Now here’s the really great news – and it’s why if the weather is clear I will be out there from 1 am on watching for Geminids. The quarter moon – which won’t interfere too much with earlier observing, sets at 1:16 am EST locally. AND – the Geminids are forecast to reach their peak at about 2 am EST. Now these forecasts are seldom right on, but they’re usually good. And I still have fond memories of a Leonid shower near the start of this century which really was a shower – the best I’ve seen in my life. And I hope to top that with this year’s Geminids.

But if the early morning peak turns you off, don’t give up on observing the Geminids. Start observing about four or five hours after sunset and you still should see enough to make it worth your while.

Where to look? They can appear anywhere. But more will be nearer the radiant. During my observing time I plan to be lying flat on my back and looking straight up. And by the way – that one or two a minute? That’s an “average.” Don’t expect to see one or two every minute. You have to look up continuously. And while you can talk to a friend, don’t let your eyes drift from the sky. Do that for at least 30 minutes and you should come close to the average – which I hope will be about one a minute. And I would be real happy with one every couple of minutes.

Finally, if you do see any, note their color – Geminids can be any of several colors – and, of course, notice how the meteor traces back to the radiant point in the sky in the constellation of Gemini. If you see a particularly bright one – take your binoculars and look where it just flashed. You ‘ll have a good chance of seeing a trail, similar to the vapor trail of a jet.

One last note: I think of most meteor showers as comet dust. That is, the Earth is passing through the dusty remnants left by a comet as it got near the Sun. But the Geminids are a bit of a puzzle here. They are believed to be associated with an asteroid known as 3200 Phaethon – only some folks feel this is not an ordinary asteroid. In fact, it is a dead comet. The jury is still out – but whatever the source, it should sprinkle some pixie dust our way December 13/14, and I hope to catch my share.

And Planets at all Hours – Jupiter, Uranus, Saturn – even Mercury and Venus, with a cameo appearance by Mars

Planet-wise, the month starts out with a bang. Jupiter and Uranus are high to the south at sunset; Saturn is getting higher and higher in the pre-dawn sky; and on December 2 there’s a terrific little triangle about an hour before sunrise of the crescent Moon, brilliant Venus, and the guidepost star, Spica. meanwhile, off to the north is another bright guidepost star, Arcturus, and Saturn is well placed above the triangle. (The Moon has a similar conjunction with Venus in the pre-dawn sky of December 31.)

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of this chart.

Binocular users can bag Uranus, the planet that about doubled the size of our solar system – the “Georgian Star.” (To learn more about Uranus, see the September post here.) Uranus can be seen with binoculars, assuming it’s well placed, any time – but it’s far easier to locate when it is right near a bright planet such as Jupiter. This is the third time this year it has come close to Jupiter, but don’t hold your breath for this to happen again soon! In other words, see it now! (Neptune went through a similar sequence last year – now it’s off to the southwest and harder to find, though if you want to look, there’s a finder chart at the Sky and Telescope Web site.)

Jupiter joins the party!

Uranus starts off the month about three degrees from Jupiter in a neat little triangle with two stars that are almost identical in brightness to the planet, which is magnitude 5.9 – 20 Piscium (5.5) and 24 Piscium (5.9). As the month goes on, Jupiter moves closer and closer until the end of the month when it’s actually inside this little triangle and less than a degree from Uranus. Here are some charts to help you pick out the distant planet from the much more distant stars that form a backdrop. The circle covers five degrees, a typical binocular field of view, though your binoculars may show more.

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of the above chart.

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of the above chart.

Click image for larger version. (Starry Nights Pro screenshot with labels added.)

Click here to download a printer-friendly version of the above chart.

The Mars/Mercury Challenge

Can you find these two planets in the bright twilight using binoculars? On December 13 if you have a location with a clear western horizon – and really clear skies, you can put this to the test. It’s detailed by Tony Flanders in Sky and Telescope for December. He suggests looking just after sunset, but he thinks the easiest time to spot them will come about half an hour after sunset. This is one of those familiar races where to see the object, you need a dark sky behind it, but as the sky gets darker, the objects gets closer to the horizon making it more difficult to see.

Actually, your success will really depend on the weather. Looking in the right place should be easy. At my latitude of 42 degrees north the Sun will set that day at azimuth 239 degrees – pretty much southwest. Half an hour later Mercury and Mars will be at azimuth 234 degrees – five degrees to the south of where the Sun set. So if it’s clear, I plan to watch the Sun set and note the spot on the horizon where it vanishes. I’ll give it about 10 minutes, then start scanning about one binocular field to the south of that spot. In 30 minutes Mars and Mercury should still be roughly three degrees above the horizon. So if I look one binocular field to the south of where the sun set and just above the horizon, my binoculars should show me two first magnitude “stars” – it should look like this.

Labels added to Starry Nights Pro screenshot.

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One Response

  1. […] had been hopelessly cloudy  here for the total lunar eclipse on December 21, 2010 so, of course, the next night it was  brilliantly clear and I marveled at the brightness of the […]

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