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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.

Not updated, but . . .

. . . charts and information about the stars in the north and east continue to be accurate month-by-month. Just choose a month from the drop down menu “categories” on the left. HOWEVER, Planets will not be accurately plotted because they change their positions constantly. However, if you identify the stars and there’s a bright interloper not on the charts, then is almost certainly a planet.

I have stopped my monthly updates of events, so the material is no longer timely here – except, of course, the relatively timeless material about the position of stars during any given month – and that is the main thrust of this site – helping you to learn the position of the bright stars as they rise in the east. Armed with this knowledge you should be able to find your way around the night sky to more obscure objects.

Happy observing and clear skies!

Look North in November into the Dragon’s Lair

Click image for larger view. Remember: This chart is for about 90 minutes after sunset.  With each passing hour these stars will rotate counter clockwise around the Polaris, the North Star.  So Vega will appear to get lower as the night goes on and Capella will be getting higher. (Prepared from Starry Nights Pro screen shot.) 

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

Our north sky map this month is covering a slightly larger area than normal because I want to capture the relationship between Vega and Capella – two of our northernmost guidepost stars – that anchor the north sky in November. Think of them as two cornerstones and a line drawn between them will go quite close to the North Star, Polaris. What’s more, Vega will help us find the head of Draco the Dragon.

Draco is one of the north sky’s more charming constellations, for its long, slithery form does call to mind a dragon. It’s quite easy to pick out, really, but you do need dark skies with little light pollution. Start by locating Vega. The four stars that mark the head of Draco – one is quite faint – will be found roughly halfway between Vega and the two bright stars that mark the end of the cup of the Little Dipper. Having located the head, you really need a chart handy to find the rest of this long, twisting, dragon body – but it is pretty easy, and once you identify it, you won’t forget it.

Draco also harbors a special treat for binocular and small telescope users. That faint star (Nu) that marks one corner of the Dragon’s head? It’s really two, perfectly matched, 4.9 magnitude stars that are far enough apart so they can be split with binoculars – assuming you have good eyes and a really steady hand. In a small telescope they are absolutely delightful and earn their nickname of Dragon’s Eyes. ( There are actually three neat double stars in this region that are a delight for the telescope user. I’ve written about them in the double star observing blog I share with my friend John Nanson.)

Meanwhile, to the east we have a bright half circle of asterisms we’ve been talking about in the previous months. Start with Capella and move on up to the “Bow” of Perseus and from there higher still to the “W” of Cassiopeia. Directly above the Pole you’ll find the “Home Plate” of Cepheus pointing down towards Polaris.

Look East in October 2014! See a bow, the demon star, and a distant galaxy

On tap this month are:


To begin our monthly exploration of the night sky in the east, you can take a slide down Andromeda’s Couch to Mirfak and the Bow of Perseus in the northeast – that is, you can if you learned how to find Andromeda’s Couch last month. If that’s new to you, ignore it for now and simply start by looking for the “Bow” of three bright stars rising low in the northeast.

To find it, go out about an hour after sunset and watch the bright stars emerge. It may take a few minutes to see the bow clearly, but what you are looking for is three stars in a vertical arc, with the middle one – Mirfak – the brightest. How big an arc are we talking about? Just make a fist and hold it vertically at arm’s length, and your fist should just cover these three stars. How high? The bottom one should be about a fist above the horizon. Here’s a chart modified from Starry Nights Pro software.

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

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

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

For a printer friendly version of this chart go here.

The bow asterism is the core of the constellation Perseus. Now if you want to be a stickler about mythology, Perseus usually is not depicted with  a bow – he wields a sword instead, which he is holding in his right hand high over his head, while in the left hand he holds the severed head of Medusa. Here’s how the 1822 “Urania’s Mirror” depicted him.

perseus
Perseus – click for a larger version.

Oh boy – and if you can see all that in these stars, then you have a very vivid imagination. I never would have learned the night sky if I had to try to trace out these complex constellations as imagined by ancient cultures and depicted in star guides up until fairly recently. And for the purposes of helping you find your way around the night sky I think remembering the “Bow of Perseus” is easier.

Getting sharp about brightness

As you start to learn the stars, it may surprise you how precise you can be about their brightness. At first you may have difficulty just telling a first magnitude star from a second, but if you get to know Algol, the “Demon Star,” I bet you’ll find that you can quickly become quite sophisticated in assessing brightness and shaving your estimates down to as little as a tenth of a magnitude. So let’s take a closer look at the Bow and three bright stars in this region – Mirfak, Algol, and Almach.

Imagine a star that regularly varies in brightness every few days – that’s what Algol does. Exactly every 2 days, 20 hours, and 49 minutes it begins a 10-hour period where its brightness dims more than a full magnitude. If you look during the right two hours, you’ll catch it at or near its dimmest – and most of the rest of the time you’ll catch it at or near peak brightness. And it’s quite easy to judge. But first let’s find it. Here’s the chart we’ll use.

Notice how Algol makes a very nice triangle with two companions, and all three stars are close to the same brightness – Almach, the northern-most star in Andromeda’s Couch; Mirfak, the central star in the Bow of Perseus; and Algol. Algol is called the “Demon Star” because it varies in brightness – and, of course, it marks the head of Medusa. Gazing directly at her turned onlookers to stone according to Greek mythology – but I hope that doesn’t worry you because I’m going to ask you to stare directly at her – or at least at Algol! In fact, that relates to our first challenge: Go out any clear night and study these three stars and decide which is the brightest. Two are equal in brightness, but one is a tad brighter than the other two. Which is it? Algol? Mirfak? Almach? (The answer is at the end of this post so you can ignore that answer until you actually have an opportunity to test yourself.)

However . . .

Because Algol is a variable, sometimes when you look at it, Algol will actually be significantly dimmer than either Mirfak or Almach. In fact, there’s a reasonable chance it will be dimmer than either of Mirfak’s two fainter companions that make up the Bow of Perseus. If, when you test yourself, this is the case, congratulations! Make note of the date and time. But that’s not the test – just fun! For the test you want the “normal” condition, which has these three nearly the same in brightness.

OK? Back to Algol. It’s a special kind of variable star known as an eclipsing binary. That is, what looks like one star to us is really two stars very close together, and when we see Algol’s light start to dim it means its companion is passing between Algol and us causing an eclipse. Since the stars are locked in orbit around one another this happens with clockwork regularity.

algol_edu

The above diagram came from this astronomy class web site which includes a more detailed scientific explanation. Since either star of the pair can cause an eclipse, there is a much fainter, secondary eclipse of Algol – really too faint to be noticed by most observers. Why is one eclipse fainter – because one star is blue and much hotter/brighter than the other star. It is when the cooler star is in front that we see the dramatic change in light.

It’s fun to catch Algol in mid eclipse, but I suggest you not read about when to do this right now. Instead, do the little challenge first. Then when you’re ready, go to the final item in this post, which explains how and when to catch Algol in eclipse and in the process, tells you the brightness of its companions.

See a few hundred billion stars at one glance!

Yes, you can do it if you have good dark skies, you have allowed your eyes to dark adapt, and you are looking at the right place. Once again, Andromeda’s Couch is our guide, and what we are looking for this time is the Great Andromeda Galaxy aka M31.

This is our “neighbor” in space if you can wrap your mind around the idea that something “just” 2.5 million light years away is a “neighbor.” As you try to do that remind yourself that a single light year is about 6 trillion miles – of course, good luck if you can imagine a trillion of anything! OK – let’s try that – quickly. If you wanted to count one million pennies, and you counted one every second, it would take you 11 days. A billion pennies would take you about 31.7 years! And a trillion pennies? 31,700 years – roughly the time that has elapsed since the earliest cave paintings. So what if you were the cabin boy on an inter-galactic spaceship charged with ticking off the miles at the rate of one mile a second on the way to Andromeda? Think you could do it? Think you would live long enough? Hardly! The task – and journey – would take you almost half a million years – or by my crude estimate 475,650 years! And that’s non-stop counting. Ohhh – are we there yet, Mom?

And yet here you are collecting photons in your backyard that got their start on the journey to your eyes some 2.5 million years ago! Even if you live under normal, light-polluted skies, you should be able to see the Andromeda Galaxy with binoculars. In fact, this is one object where the binocular view can be as rewarding as the view through a telescope. Here’s a wide field chart for mid-month and about 90 minutes after sunset. At that point the galaxy should be roughly half way up your eastern sky. (Look for it on a night when the moon isn’t in the sky and when, of course, your eyes have had at least 15 minutes to dark adapt.)

Click image for larger version.

Starting with the preceding chart – and moving to the chart below, here’s a more detailed star-by-star hop to the Andromeda Galaxy:

  1. Locate the Great Square
  2. Locate Andromeda’s Couch off the northeast corner of the Square.
  3. Go down to the middle star in the couch, then count up two stars and bingo!
  4. You can also find the general vicinity by using the western end of the “W” of Cassiopeia as if it were a huge arrowhead pointing right at the Andromeda Galaxy.

Well, “bingo” if you have been doing this with binoculars. With the naked eye it’s more an “oh yeah – I see it – I think!” But what do you expect? Think about it. The light from the near side of this object started its journey about 150,000 years before the light from the more distant side did! And think of where the human race was 2.5 million years ago when these photons began their journey – or for that matter, where all these stars really are today! Nothing is really standing still – everything is in motion.

You might also want to think about the folks who are on a planet orbiting one of those stars in the Andromeda Galaxy and looking off in our direction. What will they see? A very faint patch – certainly  fainter than what we see when we look at the Andromeda Galaxy, but in a modest  telescope  roughly similar in shape, though about two-thirds the size. Both Andromeda and the Milky Way Galaxy we inhabit are huge conglomerations of stars. We’re about 100,000 light years in diameter – Andromeda is about 150,000 light years in diameter. The Milky Way contains perhaps 100 billion stars – the Andromeda Galaxy maybe 300 billion. (Don’t quibble over the numbers – even the best estimates are just estimates. )

And yes, in a few billion years we will probably “collide” with the Andromeda Galaxy, for we are hurtling towards one another. Such galaxy collisions are not that unusual and probably aren’t as violent as the word “collision” makes them sound – but they do, in slow motion, bring about radical changes in one another.

But all that is for the professional astronomers to concern themselves with – for us, there’s the simple beauty and awe of knowing that with our naked eye – or modest binoculars – we can let the ancient photons from hundreds of billions of stars ping our brains after a journey of millions of years.

So here’s hoping for clear skies for you so you can find a winking demon and capture in your own eye the photons from a few hundred billion stars in the Andromeda Galaxy!

And now the truth about Algol and companions

Have you done the Algol test yet? Looked at Algol, Mirfak, and Almach and tried to decide which is brightest? If so, you can check your answer by continuing to read. If not, I suggest you first do that exercise, then come back to this.

Chances are that when you look at Algol, it will be at its brightest – but how can you tell? Well, as we mentioned, you can compare it to Mirfak – but there’s an even closer match with another nearby bright star – Almach. That’s the third star in Andromeda’s Couch – the one nearest Algol.

Mirfak is the brightest of the three at magnitude 1.8.

Almach is magnitude 2.1 – which is the same brightness of Algol when Algol is at its brightest – which is most of the time. OK – for the hair splitters, Almach is a tad dimmer than Algol, but the difference is far too little to be able to tell with your eye. But that makes Mirfak about one third of a magnitude brighter than the other two. That difference you should be able to see – but it does take practice.

Here’s a chart showing the magnitude of the stars near Algol that you can use to compare it to and see if it is going through an eclipse. People who look at variable stars use charts like this, but with one important exception – the numbers are given like they were whole numbers so you will not confuse a decimal point with another star. Thus, a star like Mirfak, of magnitude 1.8, would have the number “18” next to it. I broke a convention here because there are just a few bright stars on the chart, so I didn’t worry about the possible confusion of a decimal point being mistaken for another star.

So If Algol and Almach are the same, no eclipse is going on at the moment. If Algol appears dimmer than Almach, then an eclipse is in progress. If it’s as dim or dimmer than either of the companions of Mirfak in the Bow, then you can be pretty sure you’ve caught Algol at or near its darkest. In two hours – or less – it will start to brighten and will return to full brightness fairly quickly.

Catching Almach at its dimmest is fun, but not as easy as it may seem. Why? Because although an eclipse happens every few days, it may happen during the daylight hours, or in the early morning, or some other time when it’s inconvenient. And, of course, you need clear skies. So when I want to observe an Algol eclipse, I go to a handy predicting tool on the Web that you can find here.

I then note the dates and times and pick out only those dates when the times are convenient to me – that is, happening during my early evening observing sessions. Then, given the iffiness of the weather, I consider myself lucky when I  get a good look at an eclipse of Algol. What are your chances – given your weather – that it will be clear on a night when an eclipse is visible before your normal bed time?

Algol starts to noticeably dim about two hours before mid-eclipse and is back to almost full brightness two hours after mid-eclipse.

Using the Sky and Telescope Algol calculator for October 2014 I find that  just  one hits at a good time for me  – October 13, 9:25 pm EDT

Of course the dates and time may be different for you, depending on where you live, and none of us can escape the whims of the weather!

Look North in October 2014 – and find a really bright star!


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

For a printer-friendly version of this chart, click here.

When I say “really bright,” I mean Capella – and I say it because so many folks assume, quite understandably, that the North Star will be the brightest in that section of the sky. It isn’t.

Capella is one of our brightest stars, and you may catch it this month just peeping up over the northeastern horizon about an hour and a half after sunset. And it is brilliant!  When you see Capella,  compare it with the North Star  and you will get a good idea of what the word magnitude means. There are a solid two magnitudes difference between the two – or if you want to get technical, Capella is magnitude 0 and Polaris is magnitude 2.

Yes, the magnitude system goes backwards – the lower the number, the brighter the star. Each magnitude difference represents a change of about 2.5 times in brightness. So a zero magnitude star is 2.5 times as bright as a first magnitude star – and 2.5 x 2.5, or 6.25 times as bright as Polaris, a second magnitude star. And while we’re on this subject, the faintest star in the Little Dipper – it’s over in one corner of the cup – is just about magnitude five. That means Capella is 100 times as bright as that star. (OK – if you actually do the math it doesn’t come out because I rounded off the difference – it’s really 2.512 for those wanting more precision.)

In fact, there is another interesting way to look at that star – at magnitude 4.9 it is almost exactly what our Sun would look like if it were placed just 32.5 light years away. At that distance our sun would be magnitude 4.8 – and that distance is the distance we use to compare stars. That is, to get an “absolute magnitude” for them so we can compare apples with apples,  we ask ourselves how bright a star would be if it were 32.5 light years from us.

And while we’re on the subject of magnitude, the Little Dipper does give us a great range. Polaris, as we said, is magnitude 2. The other bright star in the Little Dipper is magnitude 2 also – it’s at the end of the cup away from Polaris. Sharing that end is a magnitude 3 star, and these two are known as the “Guardians of the Pole” as they are prominent, close, and like other stars, circle around the pole  every 24 hours. Most of the other stars in the Little Dipper are magnitude 4, with the one star in the far corner of the cup being magnitude 5, as noted – well, actually 4.9. There’s a chart with these magnitudes in this post. Many people who live in light-polluted areas can see only three stars in the Little Dipper – Polaris and the two Guardians of the Pole.

How faint a star can you see? Depends upon your eye sight, the light pollution in your area, the transparency of the skies on any given night, how high the star is in the sky, and, of course, your vision and dark adaption. But as a general rule of thumb magnitude 6 has been accepted as the typical naked eye limit. However, if you live in a typically light polluted suburb you may see only to 4, or worse yet, magnitude 3. And observers on mountain tops with really clear skies reliably report seeing stars as faint as magnitude 8. All of this is with the naked eye. Add ordinary binoculars and you will certainly add three to five magnitudes to the faintest star you can see. In fact, you take a huge jump in the number of stars seen just by using binoculars with 50mm objective lenses. That’s why many amateur astronomers with fine telescopes also are likely to have a pair of 10X50 binoculars that they keep handy. I always did, but more recently I stumbled upon some very inexpensive Celestron 15X70 binoculars that I love for quick peaks, though they are two powerful and large to hold steady for serious observing.

For more serious work I now use relatively expensive 10X30 image stabilized binoculars. Yes, the 30mm means they do not gather nearly as much light as the 50mm standards – but the image stabilization means they take better advantage of the light they do gather. They’re also more compact and light, so I  don’t mind carrying them for several hours.

Capella will be a “look east” guide star next month, but you can get to know it this month as you look north. And if you live in mid-northern latitudes, it will become a most familiar site. In fact, where I live – about latitude 42°N – it is in the night sky at some time every night of the year. This is because it is so far north that as it circles Polaris, it only dips below the horizon for a few hours at a time.

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.

http://www.eclipse-chasers.com/photo/Photo18.html

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.

Sky, Eye, and Camera: Special Viewing/Photo Ops for September 2014

Note: This is my first installment of a new feature. It’s a modification of the old “events” post and still is a guide to special events for the month – things happening in the sky that do not repeat from month to month but are special to a particular date. To this I have added – and put emphasis on – information about events that are particularly suitable for capture as photographs – especially photographs that convey a sense of being there and are taken with ordinary cameras.  This is in contrast to the traditional astronomy images that use special cameras to show us things we cannot see with the naked eye by taking long exposures and gathering much more light, usually using a telescope as the lens. Greg Stone

 

September 2014 gives us several special opportunities for nice, naked-eye views of stars and planets that also provide excellent photo opportunities, especially if you have a DSLR camera – or something similar where you can adjust the exposure.

August 2014 "super" Moon. (Photo by Greg Stone)

August 2014 “Super” Moon. (Photo by Greg Stone) Click image for larger version.

September 8, 2014 – “Super” Moon rising in the Earth’s Shadow/ Belt of Venus

I can’t get real excited about the “Super” Moon idea – we’ve had two this year already, and they’re really not all that unusual, or for that matter not quite as “super” as the word makes them sound.

But the full Moon rising is always a pretty sight and a very easy subject for photographers. One alert, though. The Moon is really quite small – half a degree – and so your picture may show a Moon much smaller than you remember seeing with the naked eye. This is because the full Moon  ALWAYS appears to be much larger to us when it’s near the horizon, whether “super” or not. A friend asked me recently why my picture of the Moon conveyed this sense of what he saw, while others didn’t.

The answer is simple. I used a small telephoto lens. Technically it was an 80mm, but because of the sensor on my camera, you have to add a factor of 1.6 to that to get the 35mm – or “full frame” equivalent. So in this case it was like using a 128mm telephoto on a 35mm camera.  Lots of simple cameras come with zooms that provide at least that much magnification. Use more magnification and you may end up with a real nice picture – but it may make the Moon look a lot bigger than what people saw with their naked eye.

That brings me to another major point. My whole approach to night sky photography is to try to convey a sense of being there. For that reason I don’t overdo the sensitivity of the CCD – that is, I don’t set the ISO real high – and I do keep the exposures relatively short. With the full Moon in August, I had the ISO set at  1600 – which meant I had a little noise to clean up with the editing software – and I could take the-picture at 1/160th of a second – that’s fast enough to hand hold even with the 128mm telephoto – and the the F-stop was 7.1, small enough to provide some reasonable depth of field.

That last is critical. The Moon is at infinity, but you want to also include some foreground subjects at close and mid-range to give a sense of proportion to the objects in the sky.

Moon rise time varies by your location. Where I am on the eastern seaboard of the US, the Moon will be rising roughly 20 minutes before the Sun sets on September 8th. This is going to provide an interesting  opportunity, I think, to catch the Moon in the shadow of the Earth and/or the Belt of Venus. These appear in the east shortly after sunset and after about 15 minutes start melding into the night. The shadow will be a darker blue than the sky above it and extend perhaps a fist above the horizon.  The “Belt of Venus” will be a rosy band above the shadow. Bottom line: I think the most interesting shots will be taken about 10-15 minutes after sunset.

Of course, much depends on local weather conditions. For me the trick is to know where the Moon will be rising – just a tad south of east in September 2014 – and find a spot that not only gives me a clear horizon in that direction, but also provides some interesting foreground objects to go along with the Moon.

September 20, 2014 – Algol at minimum brightness

This event – an eclipse of Algol – will be centered on 10:55 pm EDT; on the 17th a similar event will center on 11:06pm PDT. I’m not going to go into  detail about the “demon star” here. If you don’t know about it, you can read more in this earlier post.

What I do want to point out is it’s fun to see this star dim, then brighten over the course of a few hours, and if you like taking constellation pictures, it would be neat to get one of Perseus with Algol at full strength and one with Algol at full eclipse.

While these eclipses happen every few days, you’re lucky if you find one or two a month that come at a time convenient for you to watch – and then, of course, the weather has to cooperate.

September 22, 2014 – the  Fall Equinox

This is a fun time to get a picture of either sunrise or sunset. You don’t need to be right on this date -a day or two before or after will do fine. The basic idea is to show the Sun in relation to local landmarks and thus identify for yourself the general heading for east or west from any given spot.  Actually, a real nice project is to pick a scenic spot, take a picture of a sunrise or sunset as close to the Equinox as you can get, then do the same thing again from the same spot showing the Sun at the Winter and Summer Solstices and at the Spring Equinox. The four will then show the movement of the Sun along the local horizon in the course of a year.

September 24-30 – Mars and its Rival, Plus Saturn

Click for larger version - prepared from Starry Nights Pro screenshot.

Click for larger version – prepared from Starry Nights Pro screenshot.

I suggest you go out an hour after sunset and look southwest for three bright “stars” near the horizon. Two should have a reddish hue, one a yellowish hue – though honestly, with them all this close to the horizon the atmosphere may cause them to twinkle and change color.

Still, this is worth seeing and should provide an interesting photographic challenge. However, if you have been taking pictures of constellations, similar settings should work here. (I like to set the ISO at 6400 and expose for four seconds at F7.1 with the camera on a tripod, of course, and using a cable release. This, for me, gives a typical naked eye view – but you need to experiment. I also clean up the background noise in such photographs using Lightroom.)

The main attraction here is that Mars – the red planet – is near Antares, a red star. In fact, the name “Antares” means “rival of Mars” because its color rivals the obviously ruddy planet.  Saturn is farther away but has a distinctly yellowish hue. In the course of these six evenings, Mars will first draw a bit closer to Antares, then get farther away. Saturn will also get lower each night, though Mars is moving in a counter direction right now and will appear to hold its altitude – that is, be at the same height at the same time. Of course, all of these will get too close to the horizon and eventually set, so timing is important. I plan to start an hour after sunset, then see what works best over the next half hour or so as the sky gets darker, but Antares, Mars, and Saturn also get lower.

Again, the challenge for me is to include foreground objects and show the night sky as we really experience it.  Here’s a shot, for example, that I took last winter of Orion – with a quite bright Moon out of the picture to the left.

Orion as seen from the Town Farm in Westport, MA in the winter of 2014. (Photo by Greg Stone)

Orion as seen from the Town Farm in Westport, MA in the winter of 2014. (Photo by Greg Stone)

Crescent Moon and Planets  in September 2014

I see two photo opportunities to capture a crescent Moon near major planets. On September 20, 2o14, the Moon should be within about 6 degrees of Jupiter, both about one-third the way up the eastern sky an hour before dawn. As Jupiter fades, Venus may put in an appearance near the horizon, though it’s getting quite close to the Sun.

On September 27, 2014, Saturn will have an even closer encounter with the Moon in the southwestern sky at dusk. Yep – this is in the middle of the period suggested to capture Antares, Mars, and Saturn – so if the weather gives you a break you might get a crescent Moon as a bonus.

 

Look north in September 2014 – the king’s on the rise!

Yes, that’s Cepheus, the King – remember that Cassiopeia (the “W” ) is the Queen. Though Cepheus makes a familiar “home plate” asterism, it’s not nearly so memorable as the “W” of Cassiopeia, primarily because its stars are dimmer than those of the “W.” In fact, you might have difficulty picking it out at first, but here’s a tip: Follow the familiar “Pointers” of the Big Dipper to the North Star – then keep going, but not too far. The first bright star you meet will mark the tip of the Cepheus home plate – It’s about one fist away from Polaris. For comparison, the Pointer stars are nearly three times that far in the other direction.

Also coming up below the “W” is the “Bow” asterism that marks Perseus, who is carrying the head of Medusa, which contains the “Demon Star,” Algol. We’ll take that up next month when they’re higher in the sky and easier for all to see. Here’s a chart.

Click image for a larger version. (Developed from Starry Nights Pro screenshot.)

For a printer-friendly version of this chart, download this.

To review the connecting mythology, which helps me remember the related constellations, here’s the story in brief.

Cepheus and Cassiopeia have a daughter Andromeda whose beauty makes the sea nymphs jealous. They enlist Poseidon to send a sea monster to ravage the coastline of Ethiopia, the kingdom of Cepheus and Cassiopeia. To appease the monster, the good king and queen chain Andromeda to a rock along the coast, but Perseus rescues her and together they escape on Pegasus, his flying horse.

You meet Andromeda and Pegasus – the flying horse is much easier to identify as the “Great Square” – in the “Look East” post this month. Also in the “Look East”  post we detail the “Three Guides,” three stars that mark the zero hour in the equatorial coordinate system used to give a permanent address to all stars. The first of those Three Guides is Beta Cassiopeia, visible in our northeastern sky, and so on the chart with this post.

Moving from mythology to science, Cepheus is probably best known today for a special type of star called a Cepheid variable. This is a star that changes in brightness according to a very precise time table. What’s more, it was discovered that the length of a Cepheid’s cycle – that is the amount of time it takes to grow dim and then brighten again – is directly related to its absolute magnitude. The absolute magnitude of a star is a measure of how bright it really is as opposed to how bright it appears to us. (How bright it appears is, of course, related to how far away it is.) That makes Cepheid variables a sort of Rosetta Stone of the skies.

It is relatively easy to time the cycle of a variable, even if the star is quite faint from our viewpoint. These cycles usually cover a few days. If you can identify the length of this cycle, you then can know the absolute magnitude of a star. And if you know its absolute magnitude, it’s a simple matter to compare that to how bright it appears to us and thus determine its approximate distance from us.

This is a huge breakthrough. Without Cepheid variables astronomers were at a loss for determining the distance of anything that was more than a few hundred light years away. The distance to such “close” stars could be determined using a very common method known as parallax – that is, determining how the star appeared to change position slightly from opposite sides of the Earth’s orbit. But that change in position is extremely tiny and difficult to measure even with very close stars. With the Hipparcos satellite and computer analysis, it has been possible to use this parallax system for stars as far as 3,000 light years. But that still is close by astronomy standards. (Keep in mind our galaxy is about 100,000 light years across.) But Cepheid variables can even be found in other galaxies. In fact, they played a huge role in proving that “spiral nebulae” were really other “island universes” – that is, other galaxies. The Hubble Space Telescope has found Cepheids out to a distance of about 100 million light years – a huge leap from the 3,000 light years we can reach with the parallax method.

There are other ways of making an educated guess at an object’s distance, and they frequently are quite complex and indirect. But the Cepheid variable has been one of the most important tools in the astronomer’s tool kit for the past century. It was in 1908 that Henrietta Swan Leavitt, a $10.50 a week “calculator” at Harvard Observatory noticed a pattern while doing tedious work cataloging stars and saw it’s importance. Though she published a paper about it, she never really received the credit she deserved during her lifetime for this breakthrough discovery.

So when you look at this “home plate” in the sky, see if you can find the fourth magnitude star, Delta Cephei – it’s not hard to spot under good conditions. (See the chart above.) When you find it, pay homage to it for the key role it has played in unlocking the secrets of the universe – for once astronomers know the distance of an object they can make all sorts of deductions about its composition, mass, and movement.

Look east In September 2014 – and take a journey from mythology to science

As we travel September skies we’ll move from the age of mythology to the age of science.

First, the age of mythology. Had you been born a few hundred – or even a few thousand – years ago, the eastern sky in September shortly after sunset would look something like this to your imaginative eye.

For most of recorded human history different cultures turned the stars into familiar patterns that  illustrated familiar mythological stories. In our September eastern skies shortly after sunset we have a wodnerful collection of five related mythological figures - Cepeheus (king), Cassiopeia (queen), Andromeda (princess), Perseus (hero), and Pegasus, the flying horse. (Developed froma screen shot of  Starry Night Pro. Click for larger version.)

For most of recorded human history different cultures turned the stars into familiar patterns that illustrated familiar mythological stories. In our September eastern skies shortly after sunset we have a wonderful collection of five related mythological figures – Cepheus  (king), Cassiopeia  (queen), Andromeda  (princess), Perseus  (hero), and Pegasus, the flying horse. (Slightly modified screen shot from Starry Night Pro. Click for larger version.)

The tale is easy to remember. The king (Cepheus) and queen (Cassiopeia) felt their kingdom was threatened by a sea monster, so as a sacrifice to the monster they tied their daughter, Andromeda, to a coastal rock.   But don’t worry, our hero Perseus, fresh from slaying Medusa, appears to rescue Andromeda, and they ride off across the starry heavens on his faithful steed, Pegasus, the flying horse.  Really – today the king and queen  would be tried for child abuse!

Of course as usual with the ancient constellations, the figures bear only the crudest relationship to the pattern of bright stars, so a lot of imagination is required to see them.  But that said, I do find this myth an easy way to remember these five constellations. In modern times we’ve drawn complex boundaries around each constellation and used these imaginary celestial boundaries to name and locate stars.  But more importantly, we’ve developed a celestial coordinates system much along the lines of Earthly longitude and latitude.

If you imagine the Earth’s latitude lines projected onto the dome of the sky, they become circles indicating declination – how far in degrees a point is from the celestial equator. The celestial equator itself is a projection onto the sky dome of Earth’s equator.  Longitude is projected and marked in 24 hours of “right ascension” so the whole celestial clock appears to pass overhead in the course of a day. I found it difficult remembering where these hours begin until I learned about the “Three Guides.” These are three bright stars –  indicated by arrows in the chart below – that fall very close to the zero hour line of right ascension. Above them (think of these as preceding them, for they rise first)  the hours count backward from 24. Below them – think of these  as following them, since they rise afterwards – are the hours counting up from 0.

Prepared from a Starry Nights Pro screen shot - click for a larger version.

I prefer to remember my sky in terms of bright stars and asterisms, so Cassiopeia becomes the “W.” Andromeda  becomes “Andromeda’s Couch,”  and the flying horse becomes the “Great Square.”   But the Three Guides – the three bright stars indicated by arrows – allow you to see the sky in more scientific terms, for these lie on aline that is the starting point for placing a grid on the sky to create a precise address for each star in terms of its relation to  the grid. This grid is indicated above by the red lines. (Prepared from a Starry Nights Pro screen shot – click for a larger version.)

For a printer-friendly version of this chart, download this.

First, let’s look at the “Great Square” – or perhaps we should say “Great Diamond,” since that’s what it looks like when rising. Once overhead, it is certainly a square, and it forms the heart of Pegasus – the flying horse. The stars are all second and third magnitude – about the brightness of the stars in the Big Dipper – so wait until about an hour after sunset, then look east and you should be able to pick this out. Its stars mark out a huge chunk of sky that is nearly empty of naked-eye stars, which is why I sometimes call it the “Great Empty Square.”

Andromeda’s Couch, ties to the northern corner of the square. In fact, it shares a star with this corner. “Andromeda’s Couch” is just my memory device – others would simply call this “Andromeda” because that’s the name of the constellation it dominates. I have difficulty seeing the lovely maiden chained to a rock by looking at these stars.  But knowing that in myth Andromeda was a lovely woman who was rescued by Perseus, I like to think of this graceful arc of stars as her couch with her a misty fantasy figure lying there in alluring fashion. That said, notice three things about it:

1. The bright star at the right – southern – end is also a corner of the Great Square, as we mentioned. In fact, it is the brightest star in the Great Square.

2. The three brightest stars in the “couch” – I’m ignoring the second star which is fainter – the three brightest are about as close to being identical in brightness as you can get – magnitude 2.06, 2.06, and 2.09. They also are pretty equally spaced. Hold your fist at arm’s length and it should easily fit in the gaps between these stars, which means there are 10-15 degrees between each star. That’s similar to the spacing between the four stars in the “Great Square” as well.

3. The second star, as mentioned, is dimmer by more than a full magnitude (3.25), but it’s what gives this asterism a couch feeling to me – or maybe a lounge chair – marking a sharp, upward bend.

And where’s the hero Perseus? he should be nearby, right? Well he’s on his way, rising in the northeast after Cassiopeia, but we’ll leave him for next month when he’s more easily seen.

Now for the pièce de résistance!

This is a group of stars that are new to me, at least in this role, and I love them! They’re called “The Three Guides,” but I think of it as four guides They can all be tied together by a long, graceful arc that represents the great circle of zero hour right ascension – which is the “celetsial meridian” as defined in the equatorial coordinate system.

As mentioned, the equatorial coordinate system is essentially a projection of the Earth’s latitude and longitude system onto the sky to enable us to give a very precise address for any star or other celestial object, as seen from our planet. On Earth we require an arbitrary circle be chosen as the zero longitude line, and this is the circle that passes through the poles and Greenwich, England.

In the heavens we also need such a circle, and the one chosen is the one that passes through the point where the Sun crosses the celestial equator at the vernal equinox. But that point is not represented by any bright star, so how do we know where this “zero hour” circle is? We need it to put numbers to the entire system. Enter “The Three Guides.”

They start with the star Beta Cassiopeia. This is the western most star in the familiar “W”  – the one which rises first and leads the rest. (Remember – all stars appear to move westward as the earth turns.)  From there draw an arc to Alpha Andromedae. This is the star mentioned before where Andromeda and the Great Square are joined – they both share this star.

The third star of this trio is Gamma Pegasi – the star that appears to be at the bottom of the Great Square when we see it as a diamond when rising. (If this is not clear, one glance at the accompanying chart should make it so.)

When I look at this great arc, however, I always start to trace it right from the North Star, Polaris. All the great circles representing meridians of right ascension pass through the north and south celestial poles.

As you move upward from this zero line in the general direction of the Summer triangle, the hours count backwards counting the Zero Hour as 24. Move downward, towards the horizon and the hours count forward from zero. This sequence is marked on our chart around Polaris.

Taking a wide view of the “Three Guides” to incorporate the North Star and Summer Triangle as well. Here’s what we should see about an hour after sunset. Click image for larger version. (Derived from Starry Nights Pro screen shot.)

For a printer-friendly version of this chart, download this.

What’s important is to be able to visualize this one circle in the sky and connect it with the another circle crossing it at a right angle – the celestial equator. If you can do that, you will have identified the two zero points on the equatorial coordinate system and moved your knowledge of finding things in the sky from the mythological arena to the scientific one. That’s why these three “guides” excite me so. When you can look up at the night sky and see not only a dome, but a curved grid projected on it, and on this grid be able to attach meaningful numbers, then you have graduated to sky explorer, first class!

. . . and the rest of the guideposts?

If you’ve located the new September asterisms and identified The Three Guides, then it’s time to check for the more familiar stars and asterisms you might already know, assuming you have been studying the sky month by month. (If this is your first month, you can skip this section.) So here are the guidepost stars and asterisms still visible in our September skies.

  • The Summer Triangle is now high overhead, though still favoring the east. Vega, its brightest member, reaches its highest point about an hour after sunset and moves into the western sky. Altair and Deneb are still a bit east, but will cross the meridian within about three hours of sunset.
  • The “Teapot,” marking the area of the Milky Way approaching the center of our galaxy, is due south about an hour after sunset. Well into the southwest you’ll find the red star Antares that marks the heart of the Scorpion.
  • Arcturus (remember, follow the arc of the Big Dipper’s handle to Arcturus) is due west and about 25 degrees above the horizon as twilight ends.
  • The Keystone of Hercules and the circlet that marks the Northern Crown can both be found high in the western sky by tracing a line between Vega and Arcturus.

Look north in July 2014 and take the measure of your skies and eyes!

Light pollution is a big issue these days. How does it impact you? Summer is a good time to check by looking north about two hours after sunset and seeing what stars you can see in and near the Little Dipper. Why summer? Because this is when the Little Dipper should be highest in your sky – standing upwards from Polaris, the North Star. Here’s what you should see on a typical July evening when you look north from mid-northern latitudes.

In summer the faint stars of the Little Dipper are high above the North Star. Click image for larger view. (Developed from Starry Nights Pro screen shot.)

For a printer-friendly version of this chart, click here.

The Big Dipper is diving downward in the northwest but is still very high, and its handy “pointers” should get you quickly to the North Star, Polaris. Roughly opposite the Big Dipper you should see the “W” of Cassiopeia starting to make its way upward in the northeast. And unless you suffer from really terrible light pollution, you should see the two “Guardians of the Pole” – the second and third magnitude stars that mark the end of the Little Dipper. The brighter of these two is just a tad dimmer than Polaris, but since it’s higher in the sky right now and thus shining through less air to get to you, it will probably look just the same as the North Star in brightness.

To do this test you first have to wait until it is genuinely dark, and in summer that’s a bit longer than in winter. Twilight actually is divided into three steps. We have civil twilight which goes from sunset until when the Sun is six degrees below the horizon. Nautical twilight is the next period, which continues until the Sun is 12 degrees below the horizon. Then you have Astronomical Twilight until the Sun is 18 degrees below the horizon. At that point it is as dark as it will get and will remain that dark until we run the sequence in reverse as the eastern horizon nears the Sun. As a rough rule of thumb, you can consider each twilight period to last half an hour – but the exact length depends on where you are on Earth and the time of year. If you want to get precise, go to the U.S. Naval Observatory site, fill in the form you’ll find there, and you can get a table that will give you the start and end of these twilight times – or for that matter when the Moon rises, or the Sun sets. It’s very handy. (Note: the preceding link takes you to a page for US cities and towns – but there’s a second page here where you can put in the latitude and longitude for any location in the world, including in the US. )

The second thing you need to do is make sure your eyes are dark adapted. They are casually reasonably well dark adapted after you have been out for 15 minutes and have not looked at any white lights. But it can take from half an hour to an hour of protecting your eyes from any white light for them to become fully dark adapted. That doesn’t mean you have to sit around in the dark doing nothing waiting for this to happen. In the last hour or so before full darkness there are plenty of things to see – just avoid bright lights. That also means moonlight. You’re going to want to do this when the Moon is not in the sky, for it will make it difficult to see faint objects anywhere near it. In July of 2014 the last two weeks should work pretty well for the evening hours – as will the first day or two of the month.  Other evenings, the Moon will dominate the early evening sky.   (A good Moon-phase calendar can be found here, though for this purpose I find the table from the Naval Observatory for local Moon rise is also handy!)

So here’s the test:

How many stars can you see in the Little Dipper?

Remember that in the magnitude system the higher the number, the fainter the star.

The Little Dipper consists of seven stars. Three are easy – Polaris and the two “Guardians” marked “21” and “30” on the chart below. If, once you are dark adapted, you can see only one of the “Guardians,” then your skies are limited to magnitude 2 stars and brighter – very poor. If you see both, but no other stars in the Little Dipper, then your limit is magnitude 3.

On our chart below, the magnitude of each star is listed as a whole number so as not to put decimal points on the chart because they might then be confused with faint stars! So when you see a star listed as “21” that means “magnitude 2.1.”

For a printer-friendly version of this chart, click here.

Even in good, dark skies the other four stars in the Little Dipper may not be that easy to see – and the faintest ones may require averted vision – that is, don’t look exactly where the star should be. Instead, look a little to one side or the other, and the star may pop into view. That’s because the center of your eyes are not as sensitive to faint light as the outer regions of your eyes.

Here’s another little trick that may help you locate these faint stars – use binoculars. With typical, hand-held binoculars you may be able to fit all four stars of the Little Dipper’s “cup” into the same field of view. If not, get the “Guardians” in your field of view, then move just a little to where the other two stars of the “cup” should be. This does not count, of course, for the light pollution test. For that test we’re trying to determine the faintest star you can see with the naked eye. But looking first at the stars with binoculars helps assure you that they really are there! You also can trace out the handle this way, though you will have to move your binoculars to do so.

If you can locate all the stars in the Little Dipper with your naked eye, you have very dark skies – congratulations. To see how good they are – and continue to test your eyesight and dark adaption – look for the stars marked “55” and “60” on our chart.

The star marked “60” is traditionally thought of as the faintest you can see with your naked eye. That’s a magnitude 6 star. In really pristine skies, such as those over Mauna Kea in Hawaii, experienced observers with excellent eyes can detect stars down to magnitude 8 with the naked eye. Personally, I’m happy when I can see all the stars in the Little Dipper and especially happy if I can get that “55” star – I’ve never seen the “60” one with my naked eye. But relative to the heavily light-polluted eastern seaboard of the US, I have dark skies.

This is not simply a good guide to light pollution in your area. It also is a handy guide to tell you just how good  – how “transparent” – the skies are on any given night – and to show you how well you have dark adapted at any given moment. So whenever I go out to observe I frequently glance at the Little Dipper to test both my developing night vision and the clarity of the skies. (It never fails to amaze me how much and how quickly my night vision changes. )

To the casual observer all clear nights are equal. But the experienced star gazer knows they are not, and the stars in and about the Little Dipper are a good guide, especially in the summer months when they are so high in the sky.

Look Southeast in July 2014 – Colorful Stars and Planets, Great Asterisms – even a Great Constellation!

We’re going to cheat a little this month and look quite a bit south of east, rather than due east. The reason is we have some wonderful stars getting as high as they get if we look that way – AND we have two bright planet and colorful planets, Saturn and Mars which make for some interesting comparisons with nearby stars. We also have a couple of really cool asterisms and even a great constellation.

I’m not a big fan of constellations. Most don’t look anything like their names imply; some are quite obscure; and many simply can’t be seen in typical suburban skies these evening because of light pollution. Scorpius is an exception. It looks like the Scorpion of its name – a truly beautiful constellation with its graceful, curving tail. What’s more, many of its brighter stars actually do hang out together – they are not just an accident of our line of sight.

The Scorpion as Bayer saw him in his 1603 illustrated star atlas, Uranometria. Click for a much larger image. (Used by permission from the Linda Hall Library of Science, Engineering & Technology.)

It dominates our southeastern sky in July, just as the Summer Triangle – a terrific asterism, dominates our eastern sky this month. And we have two fascinating new “guide” stars – the intriguingly close and rapidly spinning Altair – and the incredibly huge and red Antares that is right at the heart of the Scorpion!

Antares begs comparison with Mars – both being red. But Mars is also very, very close to a bright blue star, Spica. Mars will be just a bit brighter than either of these comparison stars. Saturn –  between Mars and Antares and also very bright, has a yellowish hue.

But the real treat at this time of year remain these southern stars. They never get real high and from mid-nothern latitudes we only get a couple hours on a summer night when they are really well in view above the southern horizon. To top it all off the Milky Way runs from Deneb in the  Summer Triangle to the tail of Scorpius,but you have to wait a couple hours after sunset before this comes out.

Let’s take a look at the chart, then examine Scorpius along with its quaint little companion, a very real looking teapot complete with “steam” coming out of its spout! Wow! Summer nights may be short, but they sure offer some nice visual treats!

Oh - about that "teapot." We won't discuss it, but you can clearly see it tagging behind the scorpion. If you have real clear skies, the Milky Way is beautiful in this area and looks like steam rising from the teapot. More on this next month. Meanwhile, click image for a larger version. (Developed from a Starry Nights Pro screen shot. )

Click to enlarge! This chart covers a bigger section of sky then we usually show. Vega, for example,  will be six fists up. Oh – about that “teapot.” We won’t discuss it, but you can clearly see it tagging behind the scorpion. If you have real clear skies, the Milky Way is beautiful in this area and looks like steam rising from the teapot. More on this next month.  (Developed from a Starry Nights Pro screen shot. )

First up is the Summer Triangle – it’s an asterism that you can’t miss, and it will grace our evening skies right up into early winter. If you’ve been following for a few months, you’ve already met its lead star, brilliant Vega. And last month we were introduced to Deneb on the other corner. In fact, we saw that we could make a quite impressive Northern Triangle out of Deneb, Vega, and Polaris. But far better known than that asterism is the Summer Triangle shown above of Vega, Deneb, and Altair.

Altair is hard to miss. It is the brightest star low in the east early on a July evening, but it is also distinctive because it has two reasonably bright companions, close on either side, that form a straight line with it. This is appropriate because it’s not hard to see Altair and those two companions as representing an eagle in flight, and that’s good because they are the major stars in a constellation known as Aquilla, the Eagle.

Altair is white, much like Deneb and Vega, and is even closer to us than Vega. Vega is 25 light years away, Altair just 16. That’s in contrast to Deneb, which you may recall is an astounding 1,425 light years (at least)  from us – astounding because even at that distance it is almost as bright as its much closer companions and some experts believe it is much more distant.

Altair also distinguishes itself by spinning incredibly fast. It takes our Sun almost a month to complete a rotation on its axis. Altair, almost twice as large as our Sun, spins once on its axis in just 10 hours. Why, I don’t know, but it’s one more reminder of how these stars, which all look pretty much the same to us because they’re so far away, all have their special traits that distinguish them as individuals.

The most obvious special trait for Antares, our other new guide star this month, is its redness – and it’s one of only four guide stars that is quite close to the ecliptic – the path of the planets. That means that reddish Mars comes close, sometimes, to reddish Antares, and that’s appropriate because the name “Antares” actually means “like Mars.” However, science tells us something else about Antares. It is huge. I mean BIG.

Get out your calculator and do a little simple math. (OK, I’ll do the math, but really – this is simple, and I think you would appreciate the numbers much more if you did the calculations yourself.) One possible source of confusion:  To visualize a sphere I use its diameter. To actually calculate things I need the radius – since a radius is half of a diameter  you’ll find me jumping back and forth between these two terms – don’t let it confuse you.)

So try this. Start with something manageable, like the Earth. It’s about 8,000 miles in diameter and that’s a number that’s fairly easy to imagine. Let’s reduce Earth to a ball 2 inches in diameter. It would have a radius, then, of one inch.

Now let’s make a scale model Sun to go with our Earth. That’s easy. The radius of the Sun is 109 times the radius of the Earth. That means the Sun will have a radius of 109 inches – roughly 9 feet. So now we have a one-inch Earth and a 9-foot Sun. So our scale model has two balls – one two inches in diameter to represent the Earth and one 18 feet in diameter to represent the Sun.

That certainly should tell you that the Sun is a lot bigger than Earth, but my problem is, these linear measures don’t give us a really good sense of the size difference. We need to visualize spheres in terms of volume. We can get a rough approximation of the  volume  of a sphere by simply cubing the radius and multiplying it by 4. If we do this for our scale model Earth we have (1 x 1 x 1) x 4 – or four cubic inches. Now to calculate the volume of our scale model Sun – in cubic inches – we multiply 109 x 109 x 109, then multiply that by 4. Wow! Well, if you tried it on your calculator I hope you said “Wow!” You should get 5,180,116. That means you can fit well over one million Earths in our Sun! That to me is a lot more impressive than the linear measure where we find the diameter of the Sun is about 109 times the diameter of Earth.

Now let’s do a similar exercise with Antares. Antares has a radius more than 800 times the Sun. Do the math. Our scale model Sun has a radius of  9 feet – our scale model Antares will have a radius in feet of 9 x 800. Man, that’s big. About 7,200 feet!  (Just remind yourself that a mile is 5,280-feet.)  So now we have three models – a 2-inch diameter Earth, an 18-foot diameter Sun, and a 14,400-foot diameter Antares – that last is approaching three miles!

Don’t bother to calculate the volume. Unless you use scientific notation, your calculator probably won’t handle it. But you get the idea. That little dot of red light we call Antares is B-I-G. And don’t forget – on this same scale the huge planet you are standing on is just 2-inches in diameter.

Here’s a graphic representation courtesy of Sakurambo:

Notice the artist didn’t even attempt to represent the Earth on this scale!

Think of it this way. If Antares were our star, both the Earth and Mars would be orbiting inside it!

That’s huge – even bigger than Deneb – which we noted last month was a “supergiant” – the same class that Antares belongs in. But Deneb would only reach about halfway to Earth – Antares would go past both Earth and Mars. Deneb, however, is a very young, very bright, very hot star, which is why it shines so brightly from such a great distance. Antares is much closer – about 600 light years vs at least 1,425 for Deneb. But Antares is old – a star in its dying stages, and is large and bright because it is so bloated. It really is quite cool as stars go – that’s why it appears red to us. But it has such a huge surface area that even from a distance of 600 light years it appears bright to us – a bit brighter in our sky than Deneb, actually.

So let’s briefly consider these four guide stars together – Vega is our “standard” star – white, about the size of the Sun, and quite close at 25 light years. Altair has some unusual features, but is still rather normal as stars go. Deneb is distinguished by being large and hot; Antares by being even larger, but relatively cool.

Vital stats for Altair (AL-tair), also known as Alpha Aquilae:

• Brilliance: Magnitude .77; its luminosity is the equal of 11 Suns.
• Distance:16.8 light years
• Spectral Types: A, main sequence
• Position: 19h:50m:47s, +08°:52′:06″

Vital stats for Antares (an-TAIR-ease), also known as Alpha Scorpii:

• Brilliance: Magnitude 1.09; its luminosity is the equal of 65,000 Suns.
• Distance: 600 light years
• Spectral Types: M, supergiant
• Position: 16h:29m:24s, -26°:25′:55″

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