Sunday, March 06, 2016

 

Issue #483: The Messier: Part II


Well, you axed for it, so here it is, part II of what will be an ongoing series covering all the Messier objects. Or, to be exact, my impressions of all the Messier objects and my advice on observing ‘em. I enjoyed your responses, by the way, and hope you’ll keep them coming in. I would love to hear about your observations of these gems.

What do the Messiers mean to me today? A lot. After spending more than a few years considering them the tame stuff, just fodder for public at outreach, I’ve come home to the good old Ms. Why? For one thing, I’ve just got tired of squinting at quasars and PGC galaxies on a monitor screen. I want the cool stuff, the pretty stuff, in an eyepiece. I want the stuff that thrilled me as a kid when I first undertook The List in 1965.

Another thing is that I’ve come to the realization that these wonderful deep sky objects never get old. You can spend a lifetime observing nothing but the Messiers and never see everything of them there is to see. I plan on doing just that with eye and eyepiece as well as a camera occasionally—well, maybe with a few detours to the more wonderful NGCs—seeing all I can of these beauties in the years remaining to me.

M6: The Butterfly Cluster

Do you like open star clusters? If you’re much beyond the novice stage, probably not. You think they are boring, don’t you? And once you get beyond the best NGC examples, most open clusters are kinda boring. Most of ‘em can be described with one standard log entry, “Sparse, not well detached from the background.” The Messier is a different kettle of fish, however. Almost every single open cluster among the Ms is wonderful no matter how experienced and jaded you are. Beginning with Scorpius’ Butterfly Cluster.

This bright, magnitude 4.6, and large, 20.0’ across, group is easy to find 10-degrees 45’ east of bright Epsilon Scorpii in the Scorpion’s tail. Just don’t mistake even larger and brighter M7 for it. M7 is down near the “stinger” stars; M6 is a bit north.

What do you get when you track it down? While it’s big enough, M6 is not so big as to confound larger telescopes. It looked pretty darned impressive even in my long focal length C11:

M 6, the Butterfly, is an engaging open cluster. Beautiful in the 35 Panoptic eyepiece. It would be even better, I'm sure, in a shorter focal length instrument, as the more dark sky you can put around it the better it looks. Its double-lobed "butterfly" shape is fairly obvious, but I have to slew around to take all of it in. 

M6
There is no question that the wider your field, the more the cluster’s looping lines of stars begin to resemble the wings of a cosmic butterfly. My best view of this group ever was, frankly, not with a telescope of any kind, but with my Zhumell Tachyon 25x100 binoculars one night at the Chiefland Astronomy Village:

I usually have a hard time seeing a butterfly here, but not tonight. With plenty of open space around the cluster, I suddenly see two arcs of stars forming wings. At 25x this cluster is almost perfectly framed, and the binoculars deliver a striking pseudo 3-D effect with the bright cluster stars standing dramatically in the foreground of this Scorpius star field.

M7:  The Ptolemy Cluster

M6 looks best in a wide-field telescope or binoculars, but such an instrument is mandatory for M7. This magnitude 3.3 galactic cluster is 80’ across, and almost challenged the field size of my big binocs. Not quite, however. The cluster was amazing in the huge glasses and the same observing run at CAV where I enjoyed the Butterfly gave me a splendid look at Ptolemy (it has been known since ancient times, and was recorded by Ptolemy in the second century A.D.):

Back down south to catch M7, a glittering sea of sapphires. It’s too big for most telescopes and just fits into the Tachyon 25x100 binoculars’  field. What do I think? “Awesome, incredible.” I am wearing out those words, but the southern sky is just that in these binoculars.

In a richest field telescope or large aperture binoculars, you should be able to count up to 80 stars here arranged in an oblong shape on a clear night with the Scorpion riding high, even if you are at a northerly latitude.

M8:  The Lagoon Nebula

For this installment, this is where things really, really get good. With M8, the justly famous Lagoon Nebula. If you want t little background on my love for this one, read this, but I can sum it up just by saying this Messier, the “summer Orion nebula,” is in my top five Ms.

The Lagoon...
That is not to say, however, that M8 is quite as good as M42. Not always, anyway. Oh, it’s big and its bright, magnitude 5.0 and 17.0’ x 15.0’, but even for moi down here on the Gulf Coast, it’s relatively low even at culmination. Not only is it in the hash down on the horizon, it is in the summertime hash—the hazes, clouds, and general muck of summer. On a poor night in the suburbs, about all you will sometimes see in addition to the open star cluster superimposed on the eastern half of the cloud is a bit of nebulosity in the vicinity of the bright star 9 Sagitarii.

If that were all there were to the Lagoon, it would definitely be at the bottom of the Messier hit list, but it is most assuredly not. Wait for a special night with M8 near culmination, or, even better, get out to the club dark site, and you will begin to believe that it does live up to the “summer Orion” moniker.

One thing you do not have to worry about is finding this object. Look to the teapot, and specifically to the area 6-degrees to the northwest of the “spout” formed by Delta, Gamma, and Epsilon Sagitarii. There, enwrapped in the star-steam of the Milky Way that is pouring out of that spout, you will immediately notice a semi-fuzzy “star,” even with a 30mm finder.

Insert an eyepiece that will give you enough field to take in the whole nebula (you might want to use a UHC filter to tamp down the sky glow that results from using relatively low power), and just enjoy this big oval cloud and its stars for a while before you begin looking for details. Even if you don’t have a too-bright sky background, you might want to use a UHC filter anyway, since one works very well on this object, pulling out much nebulosity, and doesn’t dim the beautiful stars in the field too much.

When you’ve had your fill of the overall picture, start examining the Lagoon in detail, maybe using higher magnifications to do so. The first thing you will notice from a good site is, well, the Lagoon, which is the dark lane that divides the nebula into roughly east-west halves. With a filter and good conditions, you should be able to see that the edges of this lane are not smooth, but are irregular and complex, as in my photo here. On the best nights, with sufficient aperture, you may also see the dark lane isn’t really that dark; it is filled with wisps of nebulosity.

M10...
Bump up the power some more and examine the area near the center of the western half, and you will see the famous “hourglass.” This brightest portion of the entire nebula forms a shape not unlike what is on a black widow’s back.

Finally, on the other half, the eastern half of the nebula, there’s the star cluster NGC 6530. This spangled group forms a roughly spherical shape centered on the brightest portion of the eastern half of M8. You should be able to see at least a dozen bright suns here as well as many dimmer ones. Incidentally, this cluster is now thought to be a foreground object and not really involved in the nebula.

M9

M9, which lurks in the far southern portion of the lackluster constellation Ophiuchus, is a lot like Rodney Dangerfield; it just don’t get no respect. Partly, I suppose, because it’s in a seldom visited part of a rather subdued constellation, and partly because it suffers by comparison with Ophiuchus’ two premier and much more well known globulars, M10 and M12. Still, it is an M and M9 is good.

The easiest way to find it? With goto or digital setting circles. No gots? Probably the best guidepost to M9 is magnitude 2.45 Eta Ophiuchi. Proceed 3-degrees 30’ to the southeast of Eta and you should run up against this little magnitude 8.42, 12.0’ diameter knot of stars without too much trouble. If your conditions are good, you may, repeat, may be able to see it in a 9x50 finder as a bloated “star.”

What will you see when you finally land on M9 depends, as always, on your sky, your scope, and you. On a punk night with a 4-inch telescope, it’s barely there at all sometimes, looking a lot like a distant elliptical galaxy. In an 8-inch on a fine evening from a moderately good site, M9 is moderately good with a prominent core, plenty of resolution, and an obviously elongated shape. Since its brightest suns shine at magnitude 13.5, you will want to use an 8-inch telescope on this one if possible and a 10-incher is better.

M10: The Twin Glob (with M12)

M12
M10 is the easternmost of Ophiuchus' two much-loved globulars. It is bright at magnitude 6.40, and large enough, 20.0’, to be prominent, but yet not so large as to spread its light out. If you need directions for finding it, look at your charts and you will see that it forms a near right triangle with two of Ophiuchus’ more prominent stars Han and Yed Prior (Zeta and Delta Ophiuchi, respectively).

To put it mildly, M10 is a wonder. It is the best globular star cluster in Ophiuchus, and Ophiuchus, as you probably know, is just peppered with globs. With a simple 6-inch Dobsonian from a typical suburban site, M10 shows much resolution, and not just with averted vision. At 150x from a badly compromised backyard on a hazy summer night 23 years ago, I was easily able to resolve plenty of tiny little stars surrounding the cluster’s reasonably compact core.

M11: The Wild Duck Cluster

Even people who say they don’t like open clusters like M11. Why? It’s just so beautiful. And it is so rich that it’s really more like a loose globular. Well, almost anyway. It is also trivial to find. It is in the little constellation, Scutum, but your guide to it should probably be Gamma and Iota Aquilae.  Draw a line between those two, and then extend it a near equal distance to one of Scutum’s stars, Eta Scuti. If your skies are not so hot, Iota and Eta may be a little difficult with the naked eye, but a 50mm finder will show them easily.  Anyhow, keep going for another degree and a half from Eta Scuti and you are there. The cluster will show up in almost any optical finder.

Magnitude 6.3, 14.0’ diameter M11 is lovely in any scope. It is a rich oval patch of countless tiny stars. While many open clusters appear blue in overall hue due to their numerous hot young stars, M11 always looks yellowish to me. Finally, while the cluster is called the “wild duck” because the brightest stars form a triangular shape (more apparent in binoculars or a small scope) that looks like a flock of ducks on the wing, there’s something else ducky here. Pump up the power, and you will see a dark shape  near the center of the group, that looks remarkably like a duck with outstretched wings. I swear. Go out and look when M11 comes back around and tell me I am wrong.

M12

People like to call M10 and M12, the Twin Globular Clusters of Ophiuchus. And who am I to tell them not to if they like that? If nothing else, the two are close together in the sky, being separated by only a bit more than 3-degrees. That is about the extent of their twin-ness, though; you’ll find that in the eyepiece the two look absolutely nothing alike.

You have to get to M12 first, of course, and if you don’t have a computer hand control to punch M, 1, and 2 into, the best way to approach it is by noting that M12 forms an almost (but not quite) equilateral triangle with Yed Prior and Han. Or, if you are starting out from M10, just nudge your scope to the west for 3-degrees or so and you’ll see M12 in the field without too much difficulty.

While the cluster will stand out in the eyepiece, don’t expect it to put your eye out. It is considerably more subdued than its supposed twin, M10. You know what M12 reminds me of? Spring’s loose globular cluster, M53. And that is the heart of the matter concerning this one: it is looser than M10 and that makes it appear somewhat dim despite it being, at magnitude 6.1, brighter than M10. Still good, though, as my log entry from that long ago backyard summer night says:

Much resolution at 127x and 220x with the 6-inch Dob. The loose core is not completely resolved, but numerous stars put in appearances in the halo around it. The cluster’s shape looks odd, with an almost square appearance.

Next? I don’t know if we will get to our next group of Ms next Sunday or not. If the sky cooperates, I hope to bring you a dark-site report concerning my new 6-inch achromatic refractor instead.

Comments:
This is one of my Sunday staple morning reads. Like you I visit the Messier's a lot more visually, cause they are stunning. Keep the posts coming!
 
Thanks, Rod. I'm not really an open cluster guy, but recent observations of these objects along the winter Milky Way with the AR102 have inspired me to take the occasional break from galaxies to check them (and globulars) out. Great post.
 
Boy, your sky must be very murky. I can see M8 from my light polluted backyard naked eye and it is very obvious when away from lighting. Must be the difference in humidity as it is typically dry here ( classed as semi arid ) and elevation (3000 ft). I am at 49.4 N lat.
... Dwight
 
Rod,

Another winner! These two installments have been the most useful guides I've yet seen for running down the M's because we get not only hunting instructions, but more importantly a clear and detailed sense of what to look for and how some, such as M8, present themselves as almost several different objects depending on the magnification and instrument. I agree totally that the Messiers never get old, and how you almost always see something you've not previously seen in a given M each time out. Your first 10 Messiers in this series are an ideal combination of instruction and inspiration and I will probably end up printing these out so I have a permanent hard copy. They're that good. Only 90 more to go. Keep 'em coming.

And open clusters are still my favorite class of celestial objects.

Doug
Western Oregon
 
Ooops. Make that 98 more to go.

Doug
 
Rod,

You're observations with refractors lately have got me anxious to get the 100 ProED I had on backorder through Skies Unlimited since December. Couldn't pass up the sale, and I guess that was true for a few others too! (Actually, it was a Christmas present from my wife....with a somewhat strong influence from the recipient....).

John O'Hara
 
"For whom an 8-inch is small scope...."

An 8-inch telescope was a dream of mine for 20 years before I bought my first used model last summer. I still love it, but I just had to go and buy a new 9.25 last month. After five straight nights of observing with the 9.25 I decided to take the 8-inch out for old time's sake. It positively feels like a grab-and-go telescope now. I never would have thought my .20-meter beast would be a cute little thing to take out just in case the weather gets bad and on which to practice collimation.
 
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