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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.

Sky, Eye, and Camera: Special Opportunities for October 2014

Note: This is a new feature about events each month that are not only fun to observe with eye and binoculars, but are particularly suitable for capture as photographs –  especially photographs that convey a sense of being there and are taken with ordinary cameras.   While taking night sky photographs used to be more demanding, modern digital cameras don’t have to go to bed at night – they’re a great addition to your night sky enjoyment. Greg Stone

September 2013 - Full Moon rises shortly after Sunset with the Earth's shadow as backdrop, topped by the rosy "Belt of Venus." This shot was easy because the Moon is so bright.  But on October 8, 2014 I expect a similar situation in the morning western sky just before Sunrise. However, in that case the Moon won't simply be in line with the Earth's shadow - it will be in it, fully eclipsed. Under such circumstances will be able to see it?

September 2013 – Full Moon rises shortly after Sunset with the Earth’s shadow as backdrop, topped by the rosy “Belt of Venus.” This shot was easy because the Moon is so bright. But on October 8, 2014 I expect a similar situation in the western sky just before Sunrise. However, in that case the Moon won’t simply be in line with the Earth’s shadow – it will be in it, fully eclipsed. Under such circumstances will we be able to see it?

Photographing October’s Lunar Eclipse

The moon makes all sorts of news this month, but for U.S. East Coast dwellers such as me the big photo opportunity will be the total Lunar eclipse on the morning of October 8, 2014.

In addition, much of North America will see a partial solar eclipse as the Moon’s shadow falls on the Earth October 23. On October 17 and 18 the Moon plays tag with brilliant Jupiter in the morning sky. Then in the evening sky on October 27 and 28 a waxing crescent will dance above the Teapot right in the Milky Way and Mars will join it. Whew! Real lunacy this month! 😉

But I’m keeping my fingers crossed about the weather for the total lunar eclipse. This is one of four in a two-year period with others due next spring and fall. The first in this series –  last spring – was clouded out for me and I at first thought this one would be uninteresting, coming as it does, right near sunrise for my location. But that’s actually going to make it all the more interesting – especially from a photographic perspective! Here’s why.

Totality actually starts at 6:25 am EDT, 23 minutes before sunrise. Now I figure 5-10 minutes after totality begins the Earth’s shadow and the Belt of Venus should be visible in the west as they are about 15 minutes before every sunrise. But this time the Moon itself will be in that shadow.

How cool that will be! But, I’m holding my excitement because it could also be all but invisible!

It would be cool because during the typical total eclipse the Moon is in a dark sky and we can’t see the Earth’s shadow – we just know it must be there because the Moon is getting darker on one side as it moves into  it.  But this time we will have a totally eclipsed Moon sitting right inside the Earth’s shadow which we will see – weather permitting – the entire length of the western horizon.

Now I have no doubt that we will see the Earth shadow – we see it every clear morning – but will we even be able to see the Moon at that point? When totality starts the Moon will be only 4 degrees above the horizon. It sets – locally – about five minutes after sunrise. We can, of course, see even a crescent moon in broad daylight – but this is an eclipsed Moon.

So will it be visible at all and how visible? Even during the partial phases I expect it to be a little hard to pick up in a brightening sky. The partial eclipse begins at 05:15 am EDT. Astronomical Twilight – the first detectable lightening of the sky – starts a couple minutes later.

So during the partial phases we’ll have a moon that’s getting darker and darker and a sky that’s getting progressively lighter. Not much contrast. Civil Twilight begins at 06:21 for me with the moon is a tad less than five degrees above the horizon and close to totally eclipsed.

But now the question becomes how clear is the western horizon? The slightest bit of cloudiness will show up and obscure the moon when it’s at that altitude.

So the bottom line is this: I have no doubt that I will see the early stages of a partial eclipse. I simply don’t know at what point – even given perfect weather – it will start to become difficult to see and lose it’s appeal as two things work against visibility – the lightening sky and the Moon drawing closer to the horizon.

This, of course, will make it a challenging photographic target – but then remember, the camera can see things that are a bit fainter than what our naked eye sees – even with an exposure of just a second or two. Tripod needed, of course, and remote shutter release handy. But wait – we will be so close to dawn we can’t use a real slow shutter speed or it will wash everything else out. And that’s where I’m thankful for digital cameras because they’ll let us take test shots and check the results, immediately, over and over!

It’s probably a pipe dream,  but I would really like to see – and photograph – a beautiful shadow of the Earth topped by a deep red Belt of Venus with a barely detectable full Moon sitting on the horizon in the middle of the Earth’s shadow. Last year I got the full moon rising with the Earth’s shadow as a backdrop – that was neat, but of course the Moon wasn’t actually in the shadow at that point and it was at its  brightest.

Technically possible, I guess – so I’m skeptical, but please – surprise me!

In any event, here’s the complete relevant time table. The  lunar eclipse times are constant for any location, though of course you will have to convert them form EDT if you’re in a different zone. Sunrise and twilight times are strictly local. They apply to my location in southeastern Massachusetts and should be checked locally. To find them I use the service provided  by the Naval Observatory and found here.

For detailed advice on photographing a lunar eclipse go here.

Here’s my local time table – I’m at 71° 04′ W and 41° 33′ N

Lunar eclipse timetable – EDT  –  Plus Moon’s altitude

05:15 Partial eclipse begins 16.5°

05:17 Astronomical Twilight Begins     16.5°

05:49 NauticalTwilight Begins     10.4°

06:21 Civil Twilight begins 4.7°

06:25 Total eclipse begins 4°

06:48 Sun rise on horizon

06:53 Moon set

October’s Partial Solar Eclipse

From a photographic stand point I find a partial solar eclipse far, far, far less exciting than a total solar eclipse and more dangerous. You simply need to know that you shouldn’t be looking at the sun, even partially eclipsed, without special protection for you and your camera.

But if you’re in a section of North America where the partial eclipse will be good, I suggest you check out this site to find exact times for your locality – http://www.timeanddate.com/eclipse/solar/2014-october-23 

 – and then go here for observing and photographing information.


Because the Moon’s shadow seeps across the Earth during a solar eclipse, the time they occur depends on your location. With the lunar eclipse they happen at the same Universal Time everywhere as the Moon moves into the Earth’s shadow – but, of course that time has to be adjusted for time zones.

Other Special Night Sky Photo Ops in October

My goal, as always, is to include that most beautiful – and interesting – of planets, Earth, in any of my astronomical photography. To that end the idea is to look at when planets and the Moon approach closely and plan in advance what you wish to include in your Earth-sky photographs.

You don’t need a special event – or even the Moon – for this sort of thing, of course. I was photographing Saturn, Mars, and Antares with a crescent Moon low in the west over a seacoast last month. I was happy with this result.

September 27,2014 - c. 45 minutes after sunset looking west on beach in front of Allens Pond. Dartmouth, MA.  Waxing Moon with Saturn just south - plus Mars and Antares. (Click image for larger version.)

September 27,2014, an hour after sunset looking west on beach in front of Allens Pond. Dartmouth, MA. Waxing Moon with Saturn just south of it – plus Mars and Antares. (Click image for larger version.)

But I was happier when I turned around and caught the outlines of some folks sitting on a nearby large rock, as well as the glow of distance city lights to the north and the rising stars in the general area of Perseus and Triangulum. (Both these images need to be clicked on and displayed  large to see details.)

September 27,2014 - 90 minutes after sunset looking east on beach in front of Allens Pond. Dartmouth, MA.

September 27,2014 – 90 minutes after sunset looking east on beach in front of Allens Pond. Dartmouth, MA. (Click image for larger version.)

So here are the situations I would anticipate as offering some special opportunities this month.

Jupiter is quite high in the Eastern morning sky and very bright, so just about any time this month it offers a good twilight opportunity with the stars of nearby Leo. With it this high, however, you’ll probably want to be closer to foreground objects – trees, buildings, boats – whatever  – to include them.

A couple hours before sunrise you’ll find Jupiter roughly 45 degrees (4-5 fists) in the eastsoutheast and unmistakeable as the brightest “star” in the sky.

On the mornings of October 17 and 18 it will be joined by a waning crescent Moon less than 10 degrees – one fist – away – a nice combination. To take advantage of this you want to scout out locations that would offer a nice, twilight scene to the southeast.

The evening sky will offer a simlar situation, but with a waxing crescent Moon and the center of our Milky Way as background. Mars will be in the vicinity, but the distinctive “Teapot”  asterism which highlights Sagittarius will make it especially interesting. Will the Moon totally drown out the Milky Way? Certainly it will impact some of it, but this will be an interesting night sky challenge

Starting on the evening of October 26 a waxing crescent about three days old will form a rough triangle with Saturn and Antares low in the south-southwest. Antares and Saturn may be too low to see depending on how clear your horizon is.  The Moon you won’t miss.

In the next two days the Moon climbs higher and moves in the general direction of Mars, the Teapot, and the Milky Way. I think this provides an interesting combination through the 28th, but with each successive day the moon gets brighter and brighter, and thus will drown out more and more of the Milky Way in it’s area.  So I think the best opportunity will be on the 26th – but you can only be sure by getting out and seeing – and snapping.


Events December 2011 – Eclipse, Planets galore, and a very starry Christmas!

Let’s start with that very starry Christmas – I’ll be brief. If you like Christmas lore, the sky certainly cooperates this Christmas with brilliant Venus playing the role of the Christmas Star low in the southwest shortly after sunset. The sky at that time should look about like this:

Click image for larger version - Stellarium screen shot.

Click image for larger view.

And to identify what you’re seeing in the image above, click this thumbnail of the same scene.

Now – without going into great detail, suffice it to say that the Christmas Star lives in the hearts of believers,  as well as those for whom a bright star simply is a charming symbol of the season, as is a decorated tree or wreath. However, theologians and astronomers have put forth various theories over the years about what star, or comet, or combination of planets might be the “star” referenced in the Bible, and I’ve yet to encounter a single, credible explanation that makes me say – ah, that’s what it was!

But what we do have in the Christmas sky every year at this time is an asterism called the “Northern Cross.”  This is our old friend, Cygnus the Swan, who when rising in early summer appears to be flying south. Now he’s diving into the ground in the northwest and his main stars are much easier to make sense of as an upright cross asterism. The other identified stars on the chart  – Vega, Altair, and Deneb – mark the familiar “Summer Triangle,” which gets in one last shot before the wintry blasts descend on us.

And the Star of Bethlehem? Well, this year you might want to choose Venus to represent it as it begins a winter-long – and  brilliant – stand as our “evening star,” warming up the winter western sky with its shadow-casting radiance.

Great lunar eclipse as long as you don’t live where I do ;-(

My friends in Australia will have a great seat for this show on December 10-11. I won’t. Although the farther west you go in the US, the more interesting it gets, especially for early birds.

Essentially, a lunar eclipse starts with a “penumbral” eclipse, and this may give casual readers of various eclipse sites the idea that we in the east will see more than we actually will. Even on the East Coast of the US the penumbral stage of the eclipse will be underway just before the Moon sets – and that’s just half an hour before dawn.  But even under the best of conditions I find  the penumbral eclipse less than exciting – heck, I find it barely detectable. What it means is the Moon is entering the outer – dimmer – part of the Earth’s shadow. This will barely dim its light. And for us on the East Coast this will be especially difficult to notice with the Moon low in the west and us well into twilight.  So I’ve resigned myself to waiting until the next total lunar eclipse  April 14,15 of 2014 – which will be seen here.

But – elsewhere this eclipse  gets a lot more interesting. Here’s how NASA sums it up with a graphic on their eclipse web site – OK, you may need a little rocket science training to read this, but not much – be patient 😉

NASA eclipse details - see below for explanation. (You can click on this for a larger version.)

The important numbers here are in Universal Time.  To translate to your local time  go here.

The Moon enters the penumbral shadow at 11:33 Universal Time – that’s “P1” in the above graphic. For me in Massachusetts, that is 6:33 am on December 10.  For my friend John, in Oregon, that’s 3:33 am on December 10. And for my observing friends in Sydney, Australia, that’s  21:33 – 10:33 pm on December 10. See how things get better and better the farther west you go?

Unfortunately, things don’t begin to get really interesting until the umbral phase begins.  The Moon makes first contact with the dark (umbral) part of the Earth’s shadow at 12:45 UT. That’s 7:45 am for me – well after moonset and sunrise, so meaningless. Out in Oregon that’s 4:45 am, so John certainly should be able to see this phase and should see right up to the early stages of totality, though the Moon will be awfully near the horizon then – 6:06 am local time in Oregon and I imagine twilight will certainly impact the drama.

But the folks in Sydney? They get to see the whole show. Totality begins for them at 01:06 am,  Sunday December 11, 2011, with the Moon high in a dark sky.

And yes, if you haven’t figured it out by now, Europe misses this one.

If you would like to get a better handle on what’s going on – or perhaps share this experience with your kids in a meaningful way, I urge you to build my simple Earth-Moon model. I think you’ll find it fun and instructive.

Getting to know – I mean, really know – a planet when you see one

“What’s the bright star in the west right after sunset?”
I guarantee you I’ll get that question more than once in the coming months. I hope it won’t be from someone who has been reading these posts.  The truth of the matter is, we can see only five planets with our naked eye and one of those five is rare – Mercury. You have to know just when and where to look for it. But the other four are pretty darned easy to recognize on sight if you know a little about their habits and looks.
William Tyler Olcott made this clear in his wonderful  little 1907 “A Field Book of the Stars.”  Here is his short  list of rules – each of which you can put to the test any clear night this month:
If the planet is in the west, and very brilliant, it is safe to assume that it is the planet Venus.
If it is brighter than any of the fixed stars, and it is some distance from the Sun, it is doubtless the colossal Jupiter.
If it is very red it will probably be Mars.
Saturn is distinguised because of its pale, steady, yellow light.
OK, let’s  do a few “for examples.” For example, if you go out on the evening of December 26, 2011, about an hour after sunset, and look to the southwest, here’s what you should see.

Click for larger image - Stellarium screen shot.

Yep, that’s dominant Venus less than a fist away from the 2-day-old crescent Moon and both pretty near to where the Sun set an hour ago.  And when you think about it, you’re always going to see Venus somewhere relatively close to the Sun. From our perspective it swings to one side of the Sun for several months, then to the other side of it, since its orbit is closer to the Sun than ours. This coming winter it will get about as far away from the Sun as it can get, before starting to fall back towards it, so this is a good time to watch it – check on its progress from week to week.
What this means is it will frequently be an “evening star” in our western sky – BUT, though Olcott didn’t mention this – it will just as frequently be a “morning star” dominating the eastern sky before sunrise.
Mercury does the same thing – just much faster and it is doesn’t get nearly so brilliant. Last month it was in our western sky, this month it’s in the east before sunrise.
And how about Jupiter? Well, as Olcott wrote: “it is brighter than any of the fixed stars, and it is some distance from the Sun . . .” He also noted that the planets are always found in a relatively narrow arc of sky – the same one that the Sun and Moon follow – I threw the big arrow into this next screen shot to emphasize how the Moon, Venus, and Jupiter are all on the same path – that is, they are all in the plane of our solar system.
So after you locate Venus, swing your head about some to the south and look higher up. Here’s what you should see. This is for December 26, but with the exception of the Moon you should be able to see roughly the same scene any clear evening this month about 45 minutes after sunset. (OK – it will be easier to see the later in the month you look because Venus will be getting higher each night.)

Click image for larger version. This is a modified Stellarium screen shot showing a much larger area of sky than the previous one with just Venus and the Moon.

Mars, Saturn, Mercury and the Moon – a morning event

Now Mars and Saturn are a bit more problematic.  I agree with Olcott’s descriptions, but I also find it hard sometimes to distinguish between a twinkling star and a non-twinkling one that is the visual signature of a planet – and while I can readily identify star colors, they really are just tints and are not all that obvious to the unpracticed eye. Heck, I know some very experienced amateur observers who just don’t see the colors.
But to see what Olcott means, go out just about any morning this month and look to the east about an hour before sunrise.  I’ve chosen the morning of December 22 for a couple of reasons – first, the crescent Moon is in the sky and will help to guide you – and second, this happens to be the longest night of the year – the Winter Solstice, and so it’s a good time to get out and beat the drums and hope the Sun really is going to turn around again this year – stop heading south and start heading back north to chase away the winter doldrums and warm us up.

Aging Moon joins Mercury, Mars, and Saturn in the morning sky - Stellarium screen shot with labels added. Click image for larger version.

A few notes on this image: First, while Mercury is as bright as Mars, this makes it look even brighter – but it really will appear dimmer because it is so close to the horizon and in the morning twilight.  It’s about one fist away from the Moon and less than that above the horizon and will be much easier to spot if you use binoculars.  Saturn and Mars give us a lesson in color.  First, Saturn – kind of yellowish – is right next to the bluest of stars, Spica.  They both would fit in a single binocular field and Saturn is just a tad brighter.

Mars is just a bit brighter, too, and much higher – but don’t expect to see bright red. Fred Schaaf, writing in Sky and Telescope this month, says Mars plainly shows “its striking orange-yellow hue” to the naked eye this month. Yep.  Go back and forth several times between Mars, Saturn, and Spica and you should get the idea of what colors really are like in the sky. Looking at these three objects in binoculars should enhance the color a bit.

Oh – and this is the other end of that arc – the one represented by the arrow in the previous image, showing the way the planets, Sun, and Moon travel on the same path. Here the arrow should stretch from Mercury – near where the Sun will rise, to Mars. When the Sun rises, this is the general path it will follow.

A note about meteors – not this month, but be ready in early January!

The Geminids (December 13-14) are usually a great meteor shower in mid-December, but  this year the Moon will drown out all but the brightest.

However, here’s a heads-up for early January, 2012. Mark January 4, 2012, on your calendar. The rarely seem Quandrantids (I’ve caught them once and not at their best) will peak around 3 am EST on January 4. This is a shower where the peak can be spectacular – 60-200 meteors an hour– but it lasts only a couple of hours. So it’s rare to have the peak come in the early morning hours for your section of the world when the showers radiant is also at or near its highest point and when the Moon offers little or no interference.

For me a fairly bright 10-day-old Moon sets at 2:55 am – weather permitting – and it will be cold, I’m sure – I’ll start watching about 2 am and plan to stick at it until about 5 am – weather permitting.  This, by the way, is a good lesson in how “annual” astronomy events, such as the Quandrantid meteor shower, frequently become “once-in-a-lifetime” opportunities, for this will only happen if the time of the shower’s peak is just right for your location, and if the Moon isn’t interfering – and last, of course, if the local weather cooperates. That’s a lot of “ifs” and it’s why, when you get an opportunity such as this, you shouldn’t pass it up.

Oh – and don’t forget Algol!

I always check the mid-eclipse times for the coming month –  they vary depending on your location. For me the dates and times that look best are:

  • 12/10/2011 @ 08:46 pm
  • 12/13/2011 @ 05:35 pm
  • 12/30/2011 @ 10:30 pm
That means Algol will be at its dimmest for about an hour either side of those times. To make your own checks, go to the Web calculator found here.
For more details on Algol, go here.

Events for June 2011: Saturn and Porrima, Morning planets, and a total lunar eclipse for the rest of the world

Let’s start with that total lunar eclipse June 15 – it totally misses North America. But it should be quite a sight in much of the world. Take a look at this map. If you’re in the white area – or even the grey – then go to this site for more information. Otherwise – well, it still is an interesting month with Saturn running up to steal a kiss from Porrima, the morning planets continuing their show, and Mercury peeking above the western horizon late in the month.

First, here’s the lunar eclipse map.

Are you in the dark? Then you miss the eclipse. But much of the world should see all - or some phase of it this month.

Saturn and Porrima

Saturn and the beautiful double star Porrima – you need a telescope to see it as double –  continue the dance they started in May. Here’s a simulation over the  two months, prepared with Starry Nights Pro software.

Saturn is easy enough to find. Wait until an hour and a half after sunset, then look for it high in the south-southwest about 15 degrees from Spica. (Saturn will be just a tad brighter and should look yellow compared to Spica’s blue.) For the naked eye observer, watching Saturn and Porrima during June of 2011 provides a terrific opportunity to see a planet in retrograde motion – then pause,  then swing back in its normal eastward path against the background stars.  For the small telescope user it’s even better.  Porrima is a stunning double star when seen in a back-yard telescope – and Saturn, with its rings, the most awesome planet in a small telescope. During early June the pair come amazingly close – so close they’ll both fit in the same telescopic field of view in the first part of the month.  Here’s where to find them and how they will look during the first week of the month.

Click image for much larger version. Insert shows how Staurn and Porrima will look in a small telescope with a one-degree field of view. To split Porrima you will probably need a telescope with at least an 80mm objective and use 180X or more. The two will start drawing apart after about 10 days, but will still be very close at the end of the month.

You can read all about Porrima and how to split it in my friend John Nanson’s post on the star-splitting blog we share. Check it out here!

Summer Solstice and Mars

Much of the planet show is in the morning sky, as described last month. There you will find Jupiter with its retinue of four Gallilean Moons rising a bit earlier each day.  Uranus and Neptune are in the same genral vicinity, only higher. Mercury abandons the morning sky and puts in  a difficult ( for northern hemisphere observers) appearance in the evening sky near the end of the month. Mars is a bit more fun. At the start of the month it is already well past Venus and on a course that eventually takes it reasonably close to the Pleiades. As the chart shows, you should be able to fit both in the same binocular field of view by the time of the Summer Solstice.

Click image for a much larger view. (Prepared from Starry nights Pro screen shot.)

Near the end of the month (June 28, 29) the waning crescent Moon will join Mars and the Pleiades in the eastern morning sky.

Meanwhile, in the west . . .

In the last three or four days of the month you may catch Mercury, about half an hour after Sunset, moving up to join Castor and Pollux. Binoculars may be needed since they are all low and the twilight will be bright – but check it out. On the 30th they are all in a row and you can nearly cover all three  by making a fist and extending your arm.  They are all pretty close to the same brightness as well.

Click image for a larger version. (Prepared from Starry Nights Pro screen shot.)

Luna-see: Your own Earth/Moon(s) model

Yes, that’s “Moons” plural because in this little project we make two just as a matter of convenience.

The idea here is simple. I believe that concrete demonstrations stick with us and allow us to internalize abstractions – so I found the time invested in developing a simple Earth/Moon model deepened my understanding of why we see what we see, and I hope it will do the same for you. So here it is. The major abstract ideas that are made concrete here include:

  • The relative sizes not only in diameter, but volume, of the Earth and Moon.
  • The phases of the Moon and why it changes from night to night and changes position in our sky as well.
  • The true-to-scale distance between the Earth and Moon and why this simply isn’t shown in most books.
  • The reason why eclipses of the Moon do not occur at each full Moon, but are relatively rare.

Step 1

First you need to gather a few simple materials and tools. Here’s what I used, but for the wood you could easily substitute cardboard – or some other material – and use clay for the Earth ball as well as the two moons. I just like wood and found what I wanted in a local craft store that’s part of a national chain and so I assume, commonly available. Clay for the Moon balls works best because shaping them to size is a learning experience and because they cling to the wires that are used as stands – no glue needed, and you can adjust their position quickly.

Tools and materials for model - click image for larger view.

Materials needed:

1 large disc approximately 6 inches in diameter
2 small discs about 3/4-inch in diameter
1 small disc about 1/2-inch in diameter
1 1-inch ball
1 piece of string 30 inches long
2 thin, stiff wires such as used in floral arrangements – one should
be 1-inch long, the other 3-inches long

Tools needed:

pen or pencil
black felt-tipped pen (fine or very fine tip works best for writing)
small flashlight

Step 2 – Prepare a “month disc”

Using a pencil or fine ballpoint pen and protractor, carefully mark off 15 points along the perimeter of the disc, each 12 degrees apart, starting at “0”. These marks will cover half the disc.

Putting marks every 12 degrees starting at 0 and going a full 180 degrees.

Use the ruler to draw 15 lines on your disc, each going from a mark at the perimeter, through the center and clear to the other edge – this will divide the disc into 30 equal spaces, separated by 12 degrees each. Twelve degrees is the approximate amount the Moon covers in our sky each 24 hours, and the 30 divisions mark out a lunar month from New Moon through First Quarter, Full, Last Quarter and back to New.

Choose one line as your zero point, and about halfway between the perimeter and the center, place an arrowhead pointing towards the center (see highlighted area on picture above) – on this line
write “SUN” – the arrowhead indicates the direction of sunlight which for our purposes will remain constant through the month.

Considering the line just labeled as your zero point, the other lines can be numbered going counterclockwise 1-29 – the days of a lunar month – the period between two “new” Moons.

The space either side of this “0” line can be labeled “NEW.” On the other side of this line, near the perimeter, you can label the space either side of it “FULL” – Notice “NEW” moon is between the Earth and Sun; the “FULL” Moon is always opposite the Sun. You can label space 7 “FIRST QUARTER,” and on the opposite side to it, “LAST QUARTER.”

Step 3 – Adding the Earth

In the center of the disc put a small mound of clay about half-an-inch high and about an inch in diameter – take care to center this – and using the ball that is the Earth, make a depression in the top of this mound to hold the “Earth” in position at the center. (You could make the Earth ball of clay, in which case the raised mound isn’t necessary – it’s just there to keep the Earth ball from rolling away.)

If you’re satisfied everything is marked correctly, you may want to go over your labels with the black, felt tip pen to make them more prominent.

Step 4 – Adding the Moons

Make two Moons.

Take a small pinch of clay and roll it into a ball 1/4-inch in diameter. Repeat so you have two small clay balls. These represent scale models of the Moon. (The Earth is about 8,000 miles in diameter, the Moon about 2,160.) Did have trouble estimating how little clay you would need to come out at exactly one-quarter-inch in diameter? Many people do. It’s a good lesson in the difference between the diameter of a sphere and the volume.)

Put another small mound of clay about half-an-inch high on the 1/2-inch disc.

Place the short wire in the center of this mound so it is sticking straight up.

Place one of your Moons on this wire.

Step 5 – And now the shadow

Make an Earth-shadow disc

Take a 3/4-inch disc and using a marker, crayon, or whatever – color it black on both sides. This disc represents the Earth’s shadow at the distance of the Moon from the Earth.

Position the shadow by placing a small mound of clay about half-an-inch tall on the line marked “FULL” about 3/4 of the way between the “Earth” and the perimeter of the month disc.

Stand your Earth shadow on its edge in this clay.

Time to demonstrate lunar phases

For these demonstrations we use just the month disc, Earth, and the Moon on the one-inch wire – oh, and you’ll need a flashlight, and while the room doesn’t need to be pitch black, it’s good to lower the lights.

There are two keys here:

  1. Always point your flashlight -which represents the Sun – in the same direction – the direction indicated by the arrowhead you put on the New Moon line.
  2. Always position yourself as if you were standing on the side of the Earth looking up at the Moon in your sky. Another way to think of this is if the Moon is placed at Day 3, you should place yourself so you are looking along the line that connects Day 18 and Day 3 and runs through the Earth.

Move your Moon around the perimeter of the disc. To see its phase on any given night, shine the flashlight on it to simulate sunlight – and sight along the line from the Earth to the Moon for that particular night.

Position yourself so you are looking in the direction of the arrowhead, and you will see a "new" Moon - completely dark and lost in the glare of the Sun!

The person holding this flashlight is positioned to see a 2-day-old crescent Moon - the photographer was at a somewhat different angle and so saw a larger crescent. Remember - keep flashlight pointed in the same direction and position yourself along the line that is nearest to where you have placed the Moon.

Now here we are at full Moon - oops, but we forgot the earth's shadow!

Put the Earth's shadow in place and it should be clear that - ooops, the shadow is blocking the Moon! But if it does that we would have an eclipse every full Moon - every month! Clearly we don't, so ...

You should notice one problem. When you get to full Moon, the shadow of the Earth blocks the Moon from view. This would mean there would be an eclipse every month at full Moon – but we know there isn’t. What’s wrong with our model?

Step 6 – Going full scale and setting things right!

Our model is convenient for showing the phases of the Moon – and actually keeping track of them each month by advancing the Moon on the monthly disc each day. But it has two problems. First, it doesn’t show the distance between the Earth and Moon to scale – and second, it doesn’t show that the Moon’s orbit is tilted about five degrees to the orbit of the Earth!

So here’s how we’ll correct that situation.

Take the second 3/4-inch disc and place a clay mound on it about half-an-inch high.

Place the long wire (3 inches) vertically in this piece of clay.

Place your second clay Moon on top of this wire.

Now use the string to place your new model of the Moon 30 inches from the Earth. You have now created a scale model of the Earth/Moon system. But why is the Moon so much higher than the Earth in this model? Actually, the Moon could be that much lower than the Earth as well – we are showing it in one direction only because we’re building our model on a table. The Moon, at any given moment, could be just as far below the tabletop as it is above it – or anywhere in between these two extremes!.

To show the distance to scale, place the Moon about 30 inches from the Earth.

Placing the Moon 3 inches above the table seems high – does a five-degree tilt in the Moon’s orbit really amount to that much at the distance of the Moon from the Earth?

If the table edge represents the plane of the Earth's orbit, then the string will represent the plane of the Moon's orbit, tilted five degrees to the orbit of the Earth.

Five degrees doesn’t sound like much – but this is how much the Moon’s orbit tilts with respect to the Earth. You can get a rough idea of what this means on the scale of the Earth/Moon system by using your protractor and the string. Line your protractor up with the edge of a table. Then have your string come out at five degrees from the center of the protractor. Thirty inches later you’ll find that five degrees is now represented by about three inches – the height of our second model of the Moon.

That’s why our second wire was three inches long.

And now it should be clear why we don’t have an eclipse each month. Place your Earth’s shadow out near your Moon, and you can see that most of the time the Moon is going to miss the shadow – it will either be above it or below it.

At full the Moon may be well above the Earth's shadow, well below it, or on relatively rare occasions, pass right through it - and at those time we see an eclipse of the Moon.

You can also see that the Moon might pass through the shadow briefly, or it may take nearly three hours to get through it. But it won’t take 24 hours. Three is about the maximum. And so when an eclipse occurs at full Moon, the Moon for those few hours may, or may not, be in your night sky. That’s why eclipses are visible from only part of the Earth, and they may occur at any time of the day or night.

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!



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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