Sunday, April 03, 2016
Issue #487: Let’s Have Some More Ms
First of all, I was much gratified by your huge response to last
week’s article. The emails and Facebook messages I received concerning it were reassuring in that they showed I am not the only one who’s still worrying
about the goto wars. More than that, I was happy to hear most of
you think the same way I do about the subject. You, like me, mostly think what
matters in amateur astronomy is a
person’s love for the night sky; everything else is secondary.
But that was last week. This week? The promised refractor
piece will run soon, but not this time. Seems that in addition to comments on
the go-to wars story, I’ve been getting one heck of a lot of clamoring for MORE
MESSIERS, and who am I to say “no” to deep sky hungry amateurs coming off a
resolutely cloudy winter?
M20
We start out with a bang. Well, sort of. While the famous
Trifid Nebula is one of the highlights of the Messier catalog, its dirty little
secret is that it pales in comparison to the nearby Lagoon, M8, just a degree
and a half to the south. M20’s listed size, 28.0’, and magnitude, 5.0, make it
sound a little more eye-popping than it actually is—in fact, I believe the 5.2
probably has more to do with the open cluster involved in the nebula than the
nebula itself. Let’s not dance around the issue: as Messiers go, the Trifid is on the dim and
more difficult side.
At least finding M20 is no problem. From a decent site—and
“decent” does not mean your magnitude 4 backyard with the Trifid smack down on
the horizon—just scan “upward” from M8. Even if the nebula doesn’t quite show
up in your finder, looking through the main scope you should see a fuzzy something in a low power eyepiece as you move up. The
exact nature of that something will, however, vary with your aperture and your sky
quality.
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| The Trifid with the old Meade DSI... |
Undoubtedly you will notice a little bit of fuzziness around
the bright double star V3791 Sgr, located near the heart of the emission
component of the Trifid. The darker your site and the larger your telescope,
the more the view will expand outward from there, from the basic cloud, to the
dark lanes radiating from it that give it its Trifid moniker.
In a 10-inch or larger telescope under excellent skies, you
may be able to divine that there are actually four “petals” of nebulosity
rather than the three implied by “trifid.” And if you have really great skies,
you may also see the reflection component, the blue part of the nebulosity,
lying on the Trifid’s northern
side—ain’t easy, though.
While a medium aperture telescope and very dark skies are
best for an impressive look at M20, you sometimes get an exceptional view with
a smaller telescope as I had one evening at my club’s (semi) dark site:
NGC 6514 is the cluster involved with
M20, the Trifid Nebula. Its slightly sparse stars are fairly attractive,
covering some 28' of space. The interest here if, of course, is the nebula.
It's remarkably good tonight, with the dark lanes standing out better than I
have ever seen them in the C8. Occasionally I get hints of the reflection
nebulosity, including hints that it is blue.
The Trifid nebula responds well to a UHC type filter, by the
way. Well, the emission component does.
Naturally, a filter totally erases the
reflection nebula.
M21
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| Ah, those wide Milky Way Vistas! |
It’s slightly unusual for successive Messier objects to be
near each other in the sky, but M21 is indeed adjacent to M20, lying about ¾
degree to the northeast of the nebula. What’s it like? I am not a big fan of
sparse open clusters, and tend to be somewhat unimpressed by this one. It’s
bright at magnitude 7.2, yeah, and relatively compact at 14.0’, but there just
isn’t much here. With my 10-inch Dob, Zelda, in the backyard, I can make out maybe
20 – 25 suns sprinkled here and there.
There is, however, a way to make M21 look really, really
good: binoculars. Not just any binoculars,
but giants. With my enormous 25x100 Zhumell Tachyons from the dark skies of
Chiefland, Florida, this whole area is a wonderland, with M8 to the south and
M21 to the north bracketing M20. And oh how good M21 looks at low power, a
beautiful knot of sparklers at 25x in a wide, wide field.
M22
Oh. My. Freaking. God. When we were talking about M13, I
think I mentioned that M5 and M22 are very competitive rivals for the title
“Best glob visible in the Northern Hemisphere.” And I believe I at least implied
M5 was ahead of M22 in that race. That is true, I suppose, if you live much
above 35-degrees north or so. South of that and it begins to be a different story
with M22 easily pulling ahead.
 |
| Wide field M22... |
M 22 is low tonight, but still
wonderful. Big oval globular. The central region is loose and large as compared
to the halo of outlying stars—the core really dominates visually. Very well
resolved. TeleVue Panoptic 27mm, 103x.
One other really great thing about M22? You don’t need a C11
to enjoy it. Years and years ago when I’d just got my Short Tube 80mm refractor,
I was out in the semi-dark suburbs seeing what it could do. M13? Not so hot. No
resolution that I could see no matter how far I pushed the magnification (100x
was really about the limit for the little thing before the optics began falling
apart). Not one lousy star. M22? That was different. Despite being far from
culmination on a spring night, I could see more than a few stars in its halo. Thanks
to its loose (but not too loose) Shapley Sawyer type, VII, this glob is easy to
resolve even in my 66mm ED scope.
M23
Continuing to the north from the Teapot for 4-degrees, we
come to our next M, another open cluster. M23 is located at the center of the
small Sagittarius star cloud, and that is an important distinction. It is
located in the star cloud, it is not the star cloud.
Otherwise? This is a large and relatively dim cluster,
magnitude 5.9, 29.0’ across. Some of its stars are in fact dim enough that they
masquerade as nebulosity in a smaller aperture telescope, but there is no real nebulosity
involved here. In my C8, I see a couple of dozen suns laid out in a fairly
shapeless fashion. Frankly, the only thing that saves this one is the basic
beauty of the area. Other than that, check it off the list and move on.
M24
The nature and identify of this object has caused a lot of heartburn
over the years. Old Chuck Messier described a large 1.5-degree across “nebula.”
But the object, the open cluster, that has often been identified as M24 in
modern times is a mere 6.0’ across. What
the—?
It seems certain Messier was not describing a smallish galactic cluster,
but something else altogether, namely the Large Sagittarius Star Cloud, a
brighter portion of one of the Milky Way’s arms. As with M23, “M24,” the cluster usually and mistakenly identified as M24, is in the star cloud, but it is not the
star cloud.
So, you wanna see the real M24? Get those binoculars—15x70s
do a good job on it from a dark site—and scan to the north-northeast of
the Trifid. When you notice what looks like a detached portion of the Milky
Way, you are there; you have conquered the object Messier recorded.
If you like, however, you can also have a look at its
usurper, NGC 6603, a thoroughly undistinguished open cluster with a magnitude
of 11.10 (!). Not that it’s that bad. In the 12-inch under very dark skies, NGC
6603 is a nice, rich, small clump of suns that looks sorta pretty. It’s just
not M24.
M25
Searching around on the Internet, you may be surprised you
don’t find much about our final Sagittarius galactic cluster for the evening, M25, and
especially not drawings of it and log entries about it from your fellow
observers. That’s because this magnitude 6.2 open cluster located 8-degrees
12.0’ due east of M23 is on the large side, 29.0’ across, almost the size of
the Full Moon. While it is fairly rich, its stars are still somewhat spread out and it
is not really very well detached from the starry background. That makes M25
more fun in big binoculars than in your main telescope (in the summertime, I
always bring binocs with me when I go out observing). Nevertheless, the cluster
still has its charms in a scope:
Nice bright, LARGE open cluster.
Best at lower power. 40-50 bright stars visible, filling the field of a 35mm
eyepiece in the C11.
Still, the 25th entry is rather staid, with
its major claim to fame being that it is one of only two Messiers that don’t
have NGC numbers. Maybe Mr. Herschel also thought this one was kinda ho-hum, too.
M26
Crikey! Not another open cluster? Yep, and not a good one. Scutum’s
Messier 26, at magnitude 9.0 and 7.0’ across, is small and dim in binoculars.
In a smaller scope, 4-inches or less, it looks a lot like a distant, unresolved
globular cluster. Or maybe a little comet sans tail, which is likely what got
Messier’s attention in the first place.
In an 8-inch or 10-inch aperture telescope, M26 is somewhat better. You’ll maybe resolve ten
stars, but that is it no matter how much you crank up the power. How do you
find the thing? The easy with is with go-to or digital setting circles,
but it’s not overly tough to get on M26’s position the old fashioned way, since
it is only 49’ east-southeast of reasonably bright Delta Scuti.
M27
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| M27 with a C8... |
Best for last. What’s the best planetary nebula in the sky?
Sorry, M57 fans, it is M27, the Dumbell Nebula in Vulpecula. The only bad thing
about the Dumbbell? It can be a little hard to locate under poor skies since it
lies among the subdued stars of the Little Fox just to the southeast of the
magnificent Northern Cross. However, even under fairly poor conditions it’s not
too hard to run down, since this planetary nebula is both big and bright,
magnitude 7.3 and 8.0’ across its longest axis.
I’ve been observing this one since I was a boy and it has
simply never disappointed. Not in my Short Tube 80, not in my 12-inch Dob, not
in any telescope I’ve turned to it. It is a wonder,
an apple-core shape of nebulosity floating in a rich and beautiful field. There
is always more to see here—clumps of nebulosity, tiny stars enwrapped in the
cloud, even a doable if not easy central star that shines at mag 13.5.—so I never
tire of admiring its lustrous beauty.
Tips? If you want to see more of the nebula, try a UHC type
filter (including the Orion Ultrablock). The beauty of a UHC is that it brings
out more nebulosity without dimming down the field stars and making the view
less attractive. Yes, an OIII will work, but it really tamps down those stars.
With the UHC in the eyepiece of my 10-inch Dobsonian, the nebula doesn’t look
like a dumbbell or an apple core anymore. The side lobes fill in and suddenly
what we have is the (American) Football Nebula.
Eyepieces and magnifications? I like a wide-field for this
one, since that just enhances the spectacle, taking in more and more of the
rich Vulpecula star field. My Panoptics do a good job here. As for power, that
depends. I like to go back and forth between closeup views and wide vistas,
hunting for details one minute, and just drinking in this thing’s majesty the
next.
And that, then, is it for this time. Going on to the nextun
would mean hitting yet another summer open cluster, and I have really had
enough of them for now. One nice thing about this bunch? You will actually be
able to go outside and take a look at them before long. Right now Sagittarius
is not well up over the eastern horizon till after 4 in the a.m., but he is
back, and he will soon be creeping into the evening heavens. You’ll be able to
marvel at all of these pretty Ms soon. Well, assuming we get some clear skies
over the course of an el Niño summer, and I must admit I am a little skeptical
about that, alas.
Comments:
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I've always liked M27 without a filter in whatever scope I am using. It was the first object I saw with a Mallincam and the amazing view had me order one the next morning....Dwight
Another excellent post, Rod. M27 sure is a favorite of mine since the 1970s, when I was a teenager growing up in Minneapolis. My views of all these objects have radically improved since moving to Bortle 3 skies 200 mile to the north over 20 years ago, but actually SEEING the features that make these objects famous still requires a good night and perseverance. Thanks for the wonderful blog.
Hi Rod,
Thanks again for a great blog. Your comment about M 27 being the best planetary for telescopic observation is one I agree with. I've found something of interest in nearly any sized scope, especially 4 inches and up, with this object. Too often I take quick glances at such showpieces before starting on objects from Phil Harrington's "Cosmic Challenge". Sometimes it's nice to really explore the detail within these brighter beauties.
Hopefully the warm pacific won't have too bad an impact on your Gulf skies this summer. I'm not sure what impact it would have on Pennsylvania. Living downwind of Lake Erie, late fall, winter and early spring are normally cloud laden in Northwest Pennsylvania. Hoping the later spring, summer and early autumn skies are decent in 2016
John O'Hara
Oil City, PA
Thanks again for a great blog. Your comment about M 27 being the best planetary for telescopic observation is one I agree with. I've found something of interest in nearly any sized scope, especially 4 inches and up, with this object. Too often I take quick glances at such showpieces before starting on objects from Phil Harrington's "Cosmic Challenge". Sometimes it's nice to really explore the detail within these brighter beauties.
Hopefully the warm pacific won't have too bad an impact on your Gulf skies this summer. I'm not sure what impact it would have on Pennsylvania. Living downwind of Lake Erie, late fall, winter and early spring are normally cloud laden in Northwest Pennsylvania. Hoping the later spring, summer and early autumn skies are decent in 2016
John O'Hara
Oil City, PA
# posted by 
: 5:37 PM
: 5:37 PM
I also want to add my thanks for this little Messier "project" of yours. You're doing Mallas and Kreimer proud!
Rod,
M27 is one of the three summer nebulas I always show newbies (M8 and M57 being the other two). I too think of it as an American football than the dumbell. If we could only change the name...
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M27 is one of the three summer nebulas I always show newbies (M8 and M57 being the other two). I too think of it as an American football than the dumbell. If we could only change the name...
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