A word about binocular observing
Binoculars occupy a spot in between telescopes and the unaided eye. Most amateur astronomers have at least one pair of binoculars, because the view through binoculars differs so much from a telescopic view. For one thing, the field of view is much greater. Second, it requires almost no setup and expensive equipment, although you can pay a lot for high end binoculars. Third, binoculars are easy to pack and easy to point. And lastly, binoculars will show many more stars than the unaided eye, even in more light-polluted areas.
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| Nikon AE 10x50 |
The second piece of equipment is a reclining chair. I recommend getting a "zero gravity chair." This will allow you to lie back and observe even very high in the sky in comfort. See my article on building a binocular chair mount for a zero gravity chair mount to maximize your viewing experience. Or go ultra simple and build my Bino Body mount, which is cheap, easy to build, and makes binocular viewing a real pleasure.
This Space Walk takes you toward the center of the galaxy, covering some of the best objects in the constellations Sagittarius, Scorpius, Scutum, Serpens, and Ophiuchus. It includes a vertical swath of the sky that should allow you to view all the objects without moving your chair. You will need a good unobstructed view to the south. The darker the sky, the better, without the Moon in the sky, as even a crescent Moon will wash out the view a bit.
Link to the mp3 audio file. Download the file to the device you will be using to listen to it in the field.
Binocular Space Walk Among the Stars - Summer Southern Milky Way - audio
Observing list for Sky Safari Plus/Pro, showing all the clusters in the order mentioned in the Space Walk.
This is in the Sky Safari .skylist format. Download to your phone or tablet and import into Sky Safari Pro or Plus. Do this by emailing the .skylist file to yourself, open the email on your device, download it, then select the file, select "open with" and choose Sky Safari. You'll get an acknowledgment that it was imported. The list will show up as "Imported List" followed by the date and time. You can rename it in Sky Safari.
Note that the Large Sagittarius Star Cloud is not identified in Sky Safari. M24, the Small Sagittarius Star Cloud, is identified in Sky Safari as the "Sagittarius Star Cloud" and is included in the list.
Chart to accompany the Binocular Space Walk. Review this prior to observing with your binoculars.
The objects and their locations within the various constellations. This view is for mid-northern latitudes, looking toward the south starting just above the horizon. North is up, west is to the right, and east is to the left. Note the outline of the Milky Way, which covers almost all of Scorpius and extends up and to the left through Sagittarius, Scutum, part of Serpens, and Aquila.
Transcript of the Space Walk
Astronomerica presents a Space Walk Among the Stars: Binocular edition.
Tonight we’re going to look at some of the showpiece objects in the southern celestial hemisphere, at least the ones visible from the northern hemisphere here on Earth. Most of these are objects that you’ll also enjoy viewing in a telescope, if you have access to one, and this Space Walk should help you in knowing where to find them and how they are situated in relation to each other. I’m sure you’ll want to revisit some of them over and over.
This Space Walk is best done in mid-summer: July or August, but can be done earlier in the year if you are out in the wee hours of the morning.
You’ll need a pair of binoculars, preferably 10x50s, but if you have a different size, just adjust expectations. Ideally, you’ll be at a dark site where you can see the Milky Way. If you’re in a very light-polluted area, you may not be able to see some or all of these objects. You’ll also want a place that has a good southern horizon, without a lot of trees or buildings blocking the view, and be away from the glare of nearby lights.
You’ll also need a reclining chair- I recommend a zero gravity chair. You can do this standing up or in a regular chair, but it’ll be more tiring, and that’s not what we’re aiming for- we want relaxation!
Set yourself facing the south. This is the direction where you have the setting sun on your right. We’ll be looking toward the center of the Milky Way Galaxy. If you can see the Milky Way, you’ll notice that it runs from the south, then roughly overhead, which tells us that the Earth, and the solar system, are not in the same plane as our galaxy- something most people assume is the case. The universe just isn’t that tidy. In fact, the solar system is tilted about 60 degrees from the plane of the galaxy, with the Earth tilted somewhat from there, too. If we were in the same plane, the Milky Way would appear as a band parallel to the southern horizon from the northern hemisphere. You can ponder that later tonight, but let’s get to our Space Walk.
We're going to start by finding the Teapot asterism with the unaided eye first. This is the main grouping making up the constellation Sagittarius, The Archer, . This is a midsummer constellation because just when it gets dark it's approaching the meridian, or its highest point in the south.
If you don’t know where to look, you can find the Teapot by looking for the red star Antares, which is the brightest star low in the south, about 30° up or so in the beginning of August, depending on the latitude of your observing site. It'll be just past the meridian in the south southwest. Remember, west is to your right. This is the main star in Scorpius, the Scorpion. The head of the scorpion, represented by three stars in roughly a vertical line, is to the right or toward the west and then a line of stars curves eastward to the left and downward to the south, ending in a little curved tail with two stars marking the stinger. Antares is roughly a third of the way from the head to the stinger, and is sometimes called the heart of the Scorpion.
Once you find Scorpius, if you just look leftward, or eastward, you'll see a dimmer constellation. That's Sagittarius. Do you see the Teapot? The Teapot has its spout to the right or toward the west and Scorpius, and its handle toward the east or left. We're going to start with the star marking the top of the teapot lid. This star is named Kaus Borealis, and bears the designation, Lambda Sagittarii.
Depending on what time of night and what day of the year you’re viewing, Sagittarius can be tilted slightly from the horizontal. As the night progresses, and also as it gets toward the
end of summer, Sagittarius will be tipping around to the west as if it's trying to pour more and more tea out of its spout.
Ten power binoculars are going to give a field of view of roughly 6.5°. Lower
powered binoculars will generally give a larger field of view, and higher power binoculars a narrower field of view. To give you an idea of this distance, 10 degrees is about the width of your fist held at arm’s length.
So you’ll be able to see a circle of sky with a diameter of about two thirds of this distance.
While looking at Lambda Sagittarii, the top star in the Teapot, bring the binoculars up to your eyes. Lambda is the top star in a triangle of three stars of about third magnitude that form
the lid of the teapot, and you can use that to verify you’ve got the right star. This triangle of stars just barely fits into a typical 10x50 field of view. Move your binoculars slightly left and down and you’ll
see the four stars marking the Teapot’s handle. These fit the field of view better, and can help you reorient yourself if you get lost in space.
When you center Lambda, you'll see a little glowing ball
up and to the left at about the 10:00 position, near the edge of your field of view,. It’s just to the left of a little triangle of stars. This is our first object, globular cluster M22. Globular clusters are huge balls of thousands or even millions of stars bound together by gravity. The stars in M22 are too dim- 11th magnitude for the brightest ones- to be seen individually in 10x50 binoculars. Instead, you’ll see it as a fuzzy ball that gets brighter toward the center.
M22, number 22 on Charles Messier’s list of comet-like objects first published in 1774, is one of the closest globulars to Earth at about 10,600 light years. To put this into perspective, the Sun’s light only takes a little over 8 minutes to arrive at Earth. The light from M22, traveling at the same speed of 186,000 miles per second, takes 10,600 years. So we are seeing it as it was 10,600 years ago. At this distance, its diameter is about 100 light years across.
M22 is also one of the brightest of the 150 or so globulars known to populate the Milky Way Galaxy. Globulars consist of older stars, and M22 is estimated to be about 12 billion years old, in a universe, mind you, that is estimated to be about 13.7 billion years old. Globulars tend to be located in the galactic halo, hovering outside of the galaxy’s core, rather than in the spiral arms where most stars and deep sky objects exist, including the Sun.
Pause the recording here to rest for a moment.
While pondering M22, you may have already noticed some starlike objects moving through your field of view. These are satellites, and
even though they have no lights on them, we can see them because they are high up above the Earth out of Earth’s shadow and they’re reflecting the sunlight. Their reflected light is easy to spot against the backdrop
of the dark sky. In the summertime you can see them pretty much the entire night. In the winter just after sunset and before sunrise are the best times because of the angle of the sun.
Back to our Space Walk. With
Lambda, the top star in the Teapot centered in the binoculars, look up and to the right at about the 1:00 position, less than half the distance from Lambda to M22, and you'll see a smaller, much fainter fuzzball. [pause]
This is another globular cluster, M28. M28 is a bit further from Earth than M22, at about 18,300 light years. Like M22, it’s about 12 billion years old.
Now
let’s move from Lambda in the direction toward M28, our smaller globular, but a little bit more to the south, or down, less than a field of view and you'll come upon a straight string of what looks like five stars
with fuzz around it. This is the Lagoon Nebula, M8, probably the next best nebula for northern hemisphere observers after the great Orion Nebula, M42, which
is visible in the winter. Those two are the only star-forming regions visible to the unaided eye from mid-northern latitudes.
What looks like the second star from the left in the line of five stars is actually fuzzier than the others, and the reason is, it's actually a star cluster, NGC 6530 (NGC stands for New General Catalog). These young, hot stars are causing the eastern part of the nebula to glow. It’s probably located just in front of the nebula.
What looks like the third star from the left in that line of five stars is actually next to the heart of the Lagoon Nebula itself. The brightest nebulosity is just to the west of it. Between the second and third
stars is the darker lane that's visible in telescopes, which gives the Lagoon Nebula its name. The nebula is estimated to be about 5,000 light years away, much closer than M22 or M28 because it’s located in a spiral
arm between us and the core of the galaxy.
The last two stars in that line of five stars are close together, with the dimmer one on the far right or western end. That fourth star, the brighter of the two end stars,
is designated 7 Sagittarii. The last star in line has just a Henry Draper six-digit designation. But it's an interesting star in a telescope because it's a double star, with a seventh magnitude primary and an eighth
magnitude secondary. The primary is actually a very close double itself, too. You'll need a telescope to see both the 7th and 8th magnitude components as separate stars.
Pause the recording to take a break, taking note of where in the sky your binoculars were pointing.
The Lagoon Nebula, M8, is a region where stars are forming from gas and dust. The young hot stars formed in this nebula ionize the gas, causing it to glow. Because it’s an emission nebula,
M8 responds well to a narrowband filter screwed into a telescope eyepiece, which creates greater contrast with the background and makes it easier to see. If you have such a filter, experiment with holding it in front of one
of the binocular eyepieces when viewing brighter and larger examples of emission nebulae, and see if it increases their visibility.
Above the Lagoon Nebula in the same field you'll see M20, the Trifid Nebula. It's in a grouping of about seven stars that are visible in the 10x50s, and you'll notice a slight bit of haze there, but nowhere near as much
as the Lagoon Nebula, as it’s much smaller.
There are actually three Messier objects in your field of view now. If you put the Lagoon Nebula at the bottom of the field, M21 is that very faint but distinct grouping of stars above the Trifid Nebula. It's actually an open star cluster but not very good for binoculars because many the stars are
fairly faint. Nevertheless, you can still see that it's a cluster. You'll know you have it because it's got two stars directly above it that look like eyes looking at you.
Now go about two fields of
view below or to the south of the Lagoon, which takes us into the constellation Scorpius, and you'll come upon a nice big open cluster. This is M7. This is a great object for binoculars, and in the 10x50s, you should see about 20 or so individual stars, concentrated in the center, with some bright outliers. M7 is also
known as Ptolemy’s Cluster. Ptolemy, the astronomer and mathematician who lived in Alexandria, Egypt, under the Romans, described it in 130 CE as a “little
cloud following the stinger of Scorpius.” Of course, he had a nice dark sky.
M7 is only about 980 light years away, and it’s only about 200 million years old. Heh- just a baby! It contains a total of about 80 stars visible in telescopes.
About two thirds
of a field of view up and to the right from M7 is another open cluster, M6. It's a bit smaller and not as rich as M7, and also quite elongated or somewhat oval shaped. In telescopes, some say it looks like a butterfly, giving it the nickname, the Butterfly Cluster. I think it looks
more like a squashed dragonfly in the telescope, but that’s just me. Except for about five stars, its stars are dimmer than M7’s, although it actually contains more stars. It’s farther away than M7, at about
1600 light years.
Now, if you move downward about a field of view from M6, you'll see two bright stars on a diagonal. These mark the stinger in the scorpion’s tail, as noted by Ptolemy. If you put your binoculars down, you can see now where you've come- from the top of the Teapot, over to the
right or west, and then down to the south or southwest, ending up on the stinger. Ouch!
Pause the recording if you need a rest.
Still looking without the binoculars, you'll notice the brightest part of the Milky Way is right about at the spout of the Teapot, as if it's steam coming out of the spout. That's
directly toward the center of our galaxy right there, and it’s designated as the Large Sagittarius Star Cloud. Gas and dust obscure the actual center of the galaxy, in which lies a black hole of approximately 4 million solar masses. You'll see the Milky Way stretching up and to the left, toward the northeast. We're
only going to go part way up there because there’s just so much to see.
Now relocate the Lagoon Nebula in your binoculars, up and right from the Teapot’s spout.
From the Lagoon let's move up and slightly left from M20, the Trifid Nebula, and the cluster M21 about a field of view, up along the Milky Way. We’ll come across a large and very rich star field, looking like a giant oval cluster with a lot of Milky Way cloudiness behind it. This is the Small Sagittarius Star Cloud, designated M24. This is another one that's great for binoculars because it's so big and you can resolve a lot of the stars. The darker the sky the more you'll see.
Pause the recording to view the Small Sagittarius Star Cloud and take a rest.
In the same field of view with the Small Sagittarius Star Cloud, if we continue to move our gaze up
the Milky Way away from the Lagoon Nebula, in other words toward the northeast, or up and left, you'll see a small fuzzy spot and then a larger fuzzy spot beyond that. Those are M18 the open cluster, and M17, the Swan Nebula, also known as the Omega Nebula. M17 has one of the brightest stars in its field just above it and slightly to the right.
M18 is about 5,000 light years away, and it’s a young cluster, only about 32 million years old. In the telescope, it’s small and rather sparse but bright, making something of a shovel or spade shape. I think it’s a better object in binoculars than in a telescope.
The gas of M17 actually forms just half of the Greek letter Omega, and I think it looks a lot more like a Swan, or actually a duck, in the telescope. It’s another star forming region, like the Lagoon Nebula. It’s striking in the telescope, and like the Lagoon, responds remarkably well to a narrowband filter. It also shows good detail in the scope, including spiral-like stripes in the swan’s main body, a cloudy parachute trailing behind it, and a puff of nebulosity above the swan’s head. It’s overall “checkmark” shape may just barely be discerned in binoculars.
If you continue in the direction above the Swan Nebula, about half a field of view, you'll come to the Eagle Nebula, M16. If you put the Small Sagittarius Star Cloud at the bottom of your field, you'll see all of these objects in the same field, with M16 at the top of your field. Contained in the Eagle nebula are the “pillars of creation” made famous by the spectacular Hubble Space Telescope image. In a dark sky with a larger telescope and a narrowband filter, you can glimpse the shape of the flying eagle, which is actually one of the pillars. It's quite small, however.
Pause the recording to view these objects and take a rest.
Now drop your view back down to the Small Sagittarius Star Cloud, M24, and then to the left or the east about 2/3 of a
field of view. You'll see yet another nice open cluster, M25. Again with this one, you can make out some of the individual stars. M25 is about 2,000 light
years away. In the telescope, this cluster looks more to me like a butterfly than M7 does. It looks beautiful in a low power, wide field eyepiece.
One of our most difficult objects for the night is located just
above, or north, of M25. Put M25 at the bottom of your field of view and at the top you'll see two pairs of fairly bright stars. Halfway between the left pair and M25 is a very faint cluster. You need to use your averted
vision, looking away slightly from an object, to spot it at all. This is NGC 6645. You should be able to just make it out if you can see the Milky Way naked eye from where you're viewing. It’s very dim, but very
rich, with stars that generate just a very soft glow in binoculars. In the telescope, it’s a nice one, with an odd circular void in the center surrounded by a circlet of dim stars.
We're almost due north
of the top of the Teapot now.
Pause the recording to view these objects and take a rest.
Now let’s get back to where we were. Let's move from the top of the Teapot, above it about a field and a half,
past M25, and put those two pairs of stars that are just above NGC 6645 in your field of view. Move upwards or north from there about two thirds of a field of view, and we’ll come to a pair of stars that are about the
same separation as these two pairs. Continue up above them and slightly left about half a field of view away and you come to some brighter stars. They form a right triangle on its side with the long end pointing roughly to
the west or to the right. If you draw a line along the base of that triangle from the star on the right to the one on the left that marks the 90° angle, and continue it slightly to the left you come upon another cluster.
It's about halfway between that star marking the 90 degree angle and a cascading diagonal of stars further to the east, or left. That's open cluster M26. We're now in the constellation Scutum, the Shield.
M26 is about 5,000 light years away and about 22 light years in diameter. Like NGC 6645, it seems to have a paucity of stars in the center, in this case probably caused by an intervening cloud
of interstellar dust.
Now if we go upward, or toward the northeast at a 90° angle to the base of that triangle next to M26, about half a field of view, we come to the magnificent cluster and one of my personal
favorites, M11, the Wild Duck Cluster. This one is just a bit fuzzy in binoculars but in a telescope it's great, very rich with individually resolved stars,
and if it’s visible I almost never pass up an opportunity to look at it. It's at the end of a big arc of three bright stars that point down from the bright star Altair about 15° northeast of there, and these
stars make a good pointer when you're trying to find M11 in the telescope. You'll also see a little box of stars on the other side of M11.
If you hold your binoculars really steady you might be able to pick up a star two on the outer edges of M11 and possibly the bright star in the center of the cluster. You might also note some graininess to the cluster, which is just the beginning of resolution in binoculars.
Pause the recording to look at M11.
Now put the binoculars down and look for the shape of the constellation Aquila, the Eagle, which starts just above M11 with that arc of three stars. On the northern end of it, which is aligned with the Milky Way, you'll see the bright star Altair with a somewhat dimmer star to the northwest of it. The tail is pointing down along the Milky Way toward M11, and the wings are marked by a star on each side. There's
a star in the center between Altair, the tail, and the wings. The wings, with Altair and the center star, form a long diamond shape. Look at the star farthest to the west of that diamond, on the right, marking the wingtip
on that side.
And now look halfway between M11 and that star and you'll see a star that's a bit dimmer than any of those stars in the main shape of the constellation but the brightest in its area. Bring your binoculars up to that star, or start from M11 and move upward toward that star marking the western wingtip, about one and two thirds field of view, and it's the brightest star there halfway between the two.
It's a nice white star, and if you hold your binoculars very steady you'll see that it's a very close double, composed of two fifth magnitude white stars. This is Alya, or Theta Serpentis, in the constellation Serpens. Alya is located in a loose asterism, or grouping, of three other stars with a few dimmer stars mixed in. The two components of the double star are aligned roughly east-west. You might think that your eyes are deceiving you but it is indeed a double. At the very least it should look like a flattened star, but that's actually two stars right next to each other. This is a good test of your binoculars, your eyes, and the steadiness of your hands!
Alya and its secondary component star orbit around a common center of gravity, making a complete orbit every 14,000 years! They’re about 130 light years away from us.
Pause the recording to look at the double star Alya and rest.
Find Alya again, halfway between M11 and the western wingtip of Aquila. Now move your binoculars slowly to the right,
or toward the west, from Alya, and within the same field, a small very dim cluster will come into view, which actually isn't officially a cluster and doesn't have a designation. Just beyond that, just coming into view
as Alya is on the far left edge of your field of view, is a large and very rich cluster, but also fairly dim. This is IC 4756, “IC” for Index Catalog. It’s surrounded by brighter stars, and with averted vision you can actually make out some of the individual stars in the cluster,
although many of them are just hinted at. It almost looks like a miniature Small Sagittarius Star Cloud, M24, that we looked at earlier. This is another cluster that looks best in binoculars.
Continuing westward,
or to the right, from IC 4756, and within the same field of view, you’ll see NGC 6633, a brighter but smaller and elongated cluster, somewhat arrowhead shaped, with the point to the upper left. About 10 stars can barely be discerned individually in 10x50s. NGC 6633 makes a very nice pairing with
IC 4756 in the same field of view.
Pause the recording to admire NGC 4756 and NGC 6633 and rest. Remember where your binoculars are pointed so you can get back to this spot.
We’ve almost reached the end of this
Space Walk, but we have one more cluster to go. We’ll be moving down to the southwest, somewhat down and to the right, about two fields of view from NGC 6633. You'll see a bright star there, 2.7 magnitude .0, or
Beta Ophiuchi, a K-type orange giant star. Just above Cebalrai, or north of that, is our last open cluster, IC 4665. You can easily make out at least a dozen of the individual stars in this cluster in binoculars.
We are now perched on the right shoulder of bell-shaped Ophiuchus, the Serpent Bearer, and our memories will remain perched there until the next spacewalk.
Thanks for joining me in this Summer Southern Milky Way Space Walk Among the Stars.
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