Binocular Space Walk - Cruising for Clusters in Cassiopeia and Perseus
Download the file linked above to the device you will be using to listen to it in the field.
Observing list for Sky Safari 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.
Chart to accompany the Binocular Space Walk. Review this prior to observing with your binoculars.
The objects and their locations within the two constellations. This view is for mid-northern latitudes, looking toward the northeast on a September evening. Polaris, the North Star, is off the chart to the left.
Chart adapted from Cartes du Ciel, free sky charting software.
A word about binocular observing
You don't need a telescope to observe the night sky. Everyone likes to just look up sometimes with the unaided eye. In a dark sky it's a spectacular view, which unfortunately is becoming harder to come by with our rampant light pollution and disregard for the value of seeing the Milky Way and millions of stars.
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 simple 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.
Transcript of the Space Walk
Astronomerica presents a Space Walk Among the Stars: Binocular edition.
Tonight we’re going to go on a cruise through the northern constellation Cassiopeia, The Queen, and into Perseus, The Hero, searching for some of the brightest open star clusters. These are all between about 28 and 40 degrees from the north celestial pole, marked by the North Star, Polaris. For some in the northern hemisphere these constellations will never set, which makes them circumpolar, and for others they only just barely set, then come back up east of Polaris just an hour or two after setting.
For northern hemisphere observers, these constellation can be seen well in the evenings from late summer, through winter, when they’re at their highest, until early spring. This Space Walk is designed for September evenings, but can be reoriented to be used all winter long as the constellations appear to revolve counterclockwise around the North Pole during the night and over the fall and winter months.
You’ll need a pair of binoculars, preferably 10x50s, but if you have a different size, just adjust expectations. A typical 10x50 field of view is 6.5 degrees. With lower powered binoculars you’ll probably have a bit wider field of view. The first number, in this case 10, denotes the power.
It’s best to 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 northeastern horizon without a lot of trees or buildings blocking the view, and be away from the glare of nearby lights.
You’ll 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, especially for your neck, and we want to be comfortable.
We’ll measure distances in the sky in degrees or fields of view. 10 degrees is about the width of your fist at arm’s length, and as noted, 6.5 degrees is a typical 10x50 field of view.
We’ll be facing northeast, so first let’s find the North Star, Polaris. Pretty much everyone knows the Big Dipper, which in early Fall is low in the northwest. Polaris will be to its right. You can follow the two end stars in the bowl of the Big Dipper that point roughly toward Polaris, about 30 degrees up and to the right.
Cassiopeia is at the same distance from Polaris as the Dipper, but on the opposite side. It’s another easily recognized pattern, forming a somewhat flattened W, whose top is always oriented more or less toward Polaris. In early fall, the W is standing on its left end, and that’s how I’ll be describing directions tonight. Using north, south, east, and west for directions can get confusing any time you’re looking in binoculars or a telescope, and requires you to look away to find Polaris. It’s especially confusing near the pole. Instead, I’ll refer to up, down, right, and left for the most part, with the understanding that the W is standing on its left end. So technically up is west, down is east, left is north, and right is south. Adjust accordingly if you take the Space Walk later in the fall or winter.
Sit yourself facing Cassiopeia. We’ll be traveling vertically down from the right end of the W into Perseus, which this time of year is rising below Cassiopeia. You shouldn’t need to move your chair. The later objects will be rising higher by the time we get to them.
Note that you'll probably see satellites and maybe a few meteors as I did when I
was putting this together, including a late Perseid meteor. Also note that we'll be traversing the Milky Way so you'll see lots of star fields that don't necessarily have any designations but are still very beautiful.
And also some very interesting patterns of stars, again that don't necessarily have any official designations. If you visit this area several times you'll start to become familiar with the star patterns and be able
to find your way around better and better. If you have a telescope it'll then be much easier to find these objects because you'll know where they are in relation to each other and all of these star patterns. You might
even be able to track many of them down from memory.
Looking with your unaided eye, hopefully you can see some of the Milky Way that cuts through from Cygnus, which is about overhead on late summer or early fall evenings, down through Cassiopeia
toward the horizon. If you can't see the Milky Way then you probably won't be able to see some or all of these objects. The solution? Choose a better night or get to a darker sky.
We'll start at the
second magnitude star Caph (C-A-P-H), or Beta Cassiopeia (which is sometimes shortened to Beta Cas). Caph is at the top end of the W. You should be able to
fit Caph and the next star down in the W, Shedar (S-H-E-D-A-R), or Alpha Cas, together in your binocular field of view if you're using 10x50s. Both stars
are 2nd magnitude but Shedar is slightly brighter than Caph. It's about 5° between these two stars. Remember that a typical 10x50 field of view is about 6.5°.
Caph has a nice cascade of stars going off to the right, that is, away from Polaris, for about a third of a field of view, and if you look very closely you'll see the first three of these,
the ones closest to Caph, are multiple stars close together. The first is a grouping of three 8th magnitude stars. The second in line is a pair of 7th and 8th magnitude stars. The third is the widest pair, consisting of a
7th and 8.6 magnitude star. 10x50s should split them if you're dark adapted, use averted vision (which is looking slightly away from a dim object to see it better), and hold your binoculars steady. Smaller apertures may
have a little more trouble splitting them, as will lower powers.
Moving down to Shedar, you’ll know you have it in your binoculars because there’s an arc of four brighter stars, with the two middle stars
close together, leading off to the left to the next star in the W, Gamma Cas, which forms the middle point of the W. Gamma doesn't have a traditional name. It’s sometimes now referred to as Navi (N-A-V-I). This name was given to it by US astronaut Virgil "Gus" Grissom. It's his middle name, Ivan, spelled backwards. The name fits well, because the star
was frequently used for spacecraft navigation. Grissom died tragically in the Apollo 1 fire on the launchpad back in 1967.
Try to remember some of these brighter stars and the star patterns near them as markers
in case you get lost. But it's pretty easy to find the W just by looking up, and then looking for the star that you need.
Pause the recording here to take a break if you need one.
Now bring your binoculars up to your eyes and put Caph, the star at the right end of the W, and Shedar, the second star
down, in your field of view. Extend an imaginary line drawn from Shedar up through Caph, up and slightly left, a little more than the distance between those two, and you'll come to a faint fuzzy patch with a very dim star
at the upper edge of it. This is our first object, open cluster Messier 52, or M52.
You know you'll have M52 because it's the only little fuzzy spot in that area that's visible, and also just to the left, less than a degree, is the 5th magnitude star 4 Cas, an eruptive variable. Above 4 Cas is an arc of about five brighter stars that look like a smile. M52 is just to the right of 4 Cas.
M52, at 7th magnitude, was discovered by Charles Messier on September 7, 1774 and became number 52 in his catalog. It’s about 5,000 light years away and contains about 200 stars. I can resolve only that 8th magnitude star on its southwest edge in 10x50s. The entire cluster is about 9.5 light years across and it’s relatively young. To put these distances in perspective, light travels at about 186,000 miles per second. Per second! That’s around 671 million miles an hour. So imagine something traveling at that speed for an entire year. That’s the distance of one light year.
Less than a degree away off the side of the cluster where that 8th magnitude star resides, is the Bubble Nebula, which we would need a large telescope and a dark sky to see at all.
Pause the recording to admire M52 and rest.
Now put 4 Cas, the star just to the left of M52, on the upper left edge of your field and move your view down and right so you can also put the bright star Caph at the lower right edge of your field. If you can't fit them, you can jog back and forth slightly between the two. Draw an imaginary line between those two, and a little less than half the distance from 4 to Caph and slightly down, or to the left, is 5th magnitude 6 Cas, which is a little bit dimmer than 4 Cas, and it's surrounded by much dimmer stars. Between a quarter and a third of the way from 6 to Caph is a dim but large and very rich open cluster, NGC 7790. It's slightly elongated on the line between 6 and Caph, and in averted vision you may be able to make out about eight or so very dim stars with many dimmer ones that don't resolve. As always, averted vision, looking slightly to one side of a dim object, will reveal more detail.
NGC 7790 is an 8.5 magnitude open cluster about twice as far as M52, at about 9 or 10 thousand light years away. It’s about 70 million years old. In my 10-inch, it shows a flattened triangle
formed by three bright stars and about 20 dimmer stars.
Now put Caph back in your field of view, placing it about a third of the field from the bottom and move your binoculars slowly to the right. While Caph is
still in the field of view but heading out toward the left you'll have your view centered on NGC 7789, Caroline's Rose. This will look like a large round fuzzy spot. You won't be able to differentiate the individual stars like the last cluster, but this is a very nice cluster for telescopes of apertures of about 6 to 8 inches
or larger.
It's beautiful in my 10-inch, and you can see the dark lanes among the dense faint stars that give the illusion of looking at a rose from above, with many dim stars almost magically appearing
in averted vision. So do check it out if you have a telescope. This cluster was discovered by astronomer Caroline Herschel on Nov. 1, 1783. It consists of about 1,000 stars from 11th magnitude down to 18th. Consequently it’s a rather dim but very rich cluster in telescopes. NGC 7789 is classified
as an open or galactic cluster, and it’s about 1.5 billion years old—very old for an open cluster, but not as old as globulars. It’s about 7,600 light years away—farther than M52 but not as far as NGC
7790.
Caroline's Rose is about midway between two pairs of 5th and 6th magnitude stars, both pairs oriented roughly vertically but not exactly in the same orientation. The upper star of the left pair is Rho Cas (R-H-O), which is a semi-regular variable star dimming from about 4.5 magnitude as much as two magnitudes when it erupts, ejecting huge amounts of material. The last major eruption was in 2000. Rho is 300,000 times brighter than the Sun, and is one
of the largest stars known, with a diameter almost three times the diameter of the Earth's orbit, and one of the most luminous stars in our galaxy, yet it looks so dim because it's several thousand light years away.
Rho is a rare yellow hypergiant. Nothing up there in the sky is mundane.
Pause the recording to take in Caroline’s Rose, NGC 7789, and rest.
Now let's move downward into the W, putting Caph at the top of your field of view and Gamma, or Navi,
the middle point star, at the bottom. Almost exactly halfway between the two on a straight line is a sixth magnitude star, and just to the left of it is a very small cluster. You might be able to make out four or five individual
stars in this cluster. This is NGC 129. It’s a 6.5 magnitude cluster of about 35 stars, a little over 5,000 light years away, similar to M52. In the
10-inch, it looks like a triangle of brighter stars superimposed over a circle of about 25 dimmer ones, with a void in the center. In a wider field eyepiece, it looks like the 6th magnitude star next to it is blowing the seeds off a dandelion puffball, the cluster, with a rich spray of fainter stars on the other side of the cluster representing the seeds
flying off into the wind.
Now put NGC 129 at the top of your field and Gamma, or Navi, at the bottom, and a little more than halfway between the two and off to the left a couple of degrees is another faint cluster
looking somewhat like Caroline's Rose but a bit dimmer and a bit smaller. This is NGC 225. This 7th magnitude cluster has about 30 stars from 9th to 14th magnitude, and it’s a little over 2,000 light years away. In the telescope it looks like two flattened
arrowheads, one smaller than the other, both pointing in the same direction.
Now let's continue down the W to the next bright star, which forms the left lower point, second to last from the end of the W. This
is Ruchbah, or Delta Cas. In this orientation it's directly below Gamma and both of them should fit in your field of view. Now center Ruchbah and move
to the right about half the distance between Gamma and Ruchbah. The first reasonably bright star you come to is 5th magnitude Phi Cas (P-H-I), and you'll see a dimmer star right next to it and slightly up and right in about the 2:00 position. You'll also see a bit of fuzziness extending
up and to the left of Phi at about the 11:00 position, back toward Gamma. This is the Owl cluster, NGC 457, also known as the ET cluster. The owl is hanging somewhat upside down in this orientation, with its eyes, consisting of Phi and that dimmer star next to it, at the bottom right. 10 power binoculars are just
enough to start to resolve some of the other stars in this beautiful showpiece cluster. I can just barely make out its right wing but not it's left wing. This is a favorite telescope target for many people.
NGC 457 contains about 60 stars, and it’s not clear whether Phi and the star marking the other eye are part of the cluster or just in the line of sight. If Phi is indeed a cluster member, it would be one of the most luminous stars in the sky. The cluster members were formed from the same molecular cloud and share a common motion through space. Oh, and this is a 21 million year old owl!
Pause the recording and take a moment to examine the Owl or ET cluster...and phone home.
Now with the Owl Cluster on the right side of the field and Ruchbah on the left, look down
and left from Ruchbah about a third of the distance between the Owl and Ruchbah at about the 7:30 position and you'll see what looks like three stars very close together pointing down and right with the brightest star
in the upper left. This is the open cluster M103.
M103 contains over a hundred stars. All but the three or four that can be seen in binoculars are so faint that they really don’t show up without a telescope. About 20 to 25 stars are visible in my 6-inch scope from a moderately dark sky.
M103 was discovered in 1781 by Messier’s assistant, Pierre Mechain (“Mayshan”). It was the last object Messier added to his list. The remaining seven objects were added between 1921 and 1967 by various astronomers based on notes made by Messier and Mechain. M103 is a little over 9,000 light years away. The star visible in the upper left, or the northwest end, of the cluster is a nice double in telescopes, Struve 131, but it’s not a member of the cluster, being only about 1300 light years away, much closer than the cluster.
Now move your binoculars slowly down and to the left until the last star in the W marking the left or lower tip, Segin (S-E-G-I-N), or Epsilon Cas, comes into view. Ruchbah will still be in your upper right.
About halfway between Ruchbah and Segin and slightly downward, you'll
see a fairly bright and large open cluster with several brighter stars dominating. This is NGC 663. In the 10x50s, the cluster is dominated by two stars near the top of it, with most of the glow below those but very close. Somewhat of an egg shape. In my 6-inch, it shows about 40 stars with a dark lane cutting
asymmetrically through the cluster.
NGC 663 forms a T-shape with three stars above it as the crossbar and 663 being the stem of the T. The crossbar is longer than the stem. NGC 663 is a young cluster about 7 to
8,000 light years away, containing a total of about 400 stars.
If you look very closely at the left of the three stars forming the crossbar of the T, you'll see a little bit of very faint fuzz around it. That's because this is part of another star
cluster, NGC 654. This is a small cluster that shows about 15 stars in my 6-inch, with hints of fainter stars just beyond resolution. NGC 654 is almost 8,000
light years away, and appears to be a very young cluster, with some stars only 15 million years old. A dark nebula, (LDN 1332, 1334, and 1337), a serpentine obscuring twist of dust is just north of the cluster, adds to the
scene, making this area a prime target for astro imagers. We won’t see the dark nebula in our binoculars, though.
If you look slightly to the right of the base of the T, marked by NGC 663, not quite the length
of the crossbar but down at the level of 663, you'll come to a little flattened triangle of stars, with the brightest, 6th magnitude 44 Cas, marking the flattened point. If you look very carefully you may be able to see one of our
real challenge objects of the night, open cluster NGC 659. It’s approximately three quarters of the way from NGC 663 to that little triangle. You have
to use averted vision, hold your binoculars very steady, and if your sky is dark enough you might be able to pick up a very faint fuzzy spot there, smaller than NGC 663. That’s NGC 659. So you have three clusters very
close together in that same field. NGC 659 is not very impressive in my 6-inch, with only about 10 stars visible in something of a circle, with some faint unresolvable stars inside. This was another discovery by Caroline Herschel.
Pause the recording and take a rest.
Put Segin and Ruchbah, the two bottom stars of the W, back in your binocular field of view. Draw an imaginary line between the two, and then
a line perpendicular to that line that goes down through NGC 663. Follow that line down and to the right and you'll pass a little frown of five stars. Keep going about twice the distance from 663 to that frown and you'll
come across one of the great sights in the sky, known as the Double Cluster. We're now in the constellation Perseus.
Two clusters comprise the Double Cluster, NGC 869, on the upper right, which the brighter and more concentrated of the two, and NGC 884 to the lower left. 869 is dominated by two brighter stars that look like eyes in this orientation, and 884 has a very tiny arrow shaped asterism pointing up and left,
with the brightest star in the cluster just off the tip. In a reasonably dark sky you may be able to pick up the Double Cluster as a fuzziness between the main stars of Perseus and Cassiopeia with just your unaided eye.
The Double Cluster was cataloged by Greek astronomer Hipparchus in 130 BCE, and has been noted by many others looking up at the night sky since then. Messier was undoubtedly aware of it, but oddly didn’t include it in his catalog of comet-like objects. It wasn’t until the early 1800s that German astronomer William Herschel, the older brother of Caroline Herschel, was able to identify the object as two distinct star clusters. These are very young clusters, about 13 million years old, located about 7,500 light years away, but moving rapidly toward us, causing their light to be blue-shifted. The two clusters are close together in space, only about a few hundred light years apart. They contain several hundred blue-white supergiant stars.
Pause the recording to admire the Double Cluster and take a break.
Up and left from the upper cluster in the Double Cluster, NGC 869, you'll see a nice arc of about 9 or so stars
leading away from the Double Cluster, up and left. Just left of the end of that string of stars is an interesting large grouping that looks like a stick figure flexing its muscles. This is designated Stock 2, and is sometimes referred to as the Muscle Man Cluster. More than 30 stars are visible in the 10x50s. It looks almost as if the Muscle Man is taking the double cluster for a walk on a leash. These clusters all fit nicely in a 10x50 field of view. A wide field eyepiece
nicely frames the cluster in a telescope.
Now put the Double Cluster on the right edge of your field, which should put the Muscle Man about in the center, and on the left edge of your field you'll see kind of
a flattened triangle which looks somewhat like a cluster with a little bit of glow around it. That glow is caused by stars, but there's also nebulosity in that area. This is the Heart Nebula, Sharpless 2-190, and the cluster
is IC 1805. They are about 7,500 light years away. The radiation from the cluster causes the nebula to glow, but the nebula is a difficult telescopic observation.
I’ve only been able to spot hints of it in my 10-inch.
If you look just to the right of IC 1805, about a fifth of the way back to the Double Cluster, you'll see a little flattened grouping of tiny stars, which is cluster Markarian 6, also cataloged as Stock 7. It’s about 2,300 light years distant. You wouldn't really know this is a cluster in the binoculars. There's a lot of other
stuff around that area for the telescope and its a real playground for imagers, but not so much for the binoculars, especially after the majesty of the Double Cluster and Stock 2.
Now let's go back to the Double
Cluster and then go downward toward the horizon about half a field of view and you'll see that there's kind of an odd diagonal formation of stars cutting from the upper right to the lower left just before you get to
the first really bright star, 4th magnitude Miram, or Eta Persei. It's not quite a field of view from the double cluster. On the right end of the diagonal
pattern there are three stars almost in a vertical line with the middle one slightly offset to the left. If you take a closer look you'll see that it's part of a pattern of six stars in the shape of an elongated hexagon
with the pointed ends oriented vertically. Then going down the diagonal pattern to the left, the next grouping is an interesting cluster that reminds me of the shape of the western portion of the Veil Nebula in Cygnus. This
is again vertically oriented and is designated Trumpler 2. Trumpler 2 is about 2,000 light years away and shows about 35 stars in the shape of an elongated
X in my 6-inch. Miram, the 4th magnitude star below Trumpler 2 is the northernmost or point star in the Perseus shape. This is a good star to help guide you directly
to the Double Cluster.
Our last cluster is nice, big, and splashy. Continue going downward past Trumpler 2 and you'll pass a bunch of bright stars about a field of view below that with the brightest stars forming
a right triangle, with the right angle on the right side. Continue down and you'll see the brightest star in Perseus, 1.8 magnitude Mirfak, or Alpha Persei, and just below that is a nice big and bright splashy cluster designated Mellote 20, or the Alpha Persei Moving Group. Mirfak is the brightest member of the cluster. The whole group is framed nicely in 10x50s, probably the best instrument to view this
big and bright association of stars. The Alpha Persei Moving Group is only about 570 light years away, closer than the clusters we’ve been observing, and fills up 6 degrees of sky. Its members formed together and are
moving together through space. The cluster is about 60 million years old and contains about 500 stars.
And for a bonus, since we're in the area, we'll end up looking at the famous variable star Algol, or Beta Persei. From the Alpha Persei Moving Group, move one field of view to the right, or southwest, and 2.1 magnitude Algol will peek into view from the right. It outshines
both Kappa and Rho Persei, which can just fit in the same field with Algol at the center.
Algol is famous as an easily observed variable star, with a 10 hour long eclipse mode, occurring every 2 days, 20 hours
and 49 minutes. Algol is an eclipsing binary, and fades from its normal 2.1 magnitude down to 3.4 magnitude for two hours when its close companion star passes in front of it from our viewpoint. You can compare it to Rho Persei,
the star to the lower right of Algol within the same field of view. At its dimmest, Algol matches Rho. While Algol's eclipse times are available via Sky & Telescope's online calculator, you can keep an eye on it
night to night to see if you can catch it during an eclipse.
Being oriented along the Milky Way, Cassiopeia and Perseus have many deep sky objects for binoculars and telescopes. We’ve looked at some of the brighter ones, but there are many more for telescopic viewing. Now you should have an easier time finding your way around and can come back at your leisure with binoculars or a telescope. It’s a beautiful part of the sky.
Well, that’s it for now. I hope you enjoyed this Binocular Space Walk Among the Stars.
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