Sunday, June 12, 2016

 

Issue #497, At the Messier Halfway Point


After this installment’s M-objects, we’ll be a little more than halfway through The List, or maybe considerably more than halfway through depending on exactly which objects you believe are genuine Messiers. Anyway, the star of this week’s show is, as I said last Sunday, the Whirlpool Galaxy, M51. I made a few remarks in the previous week’s article about this rather spectacular deep sky object, to include my choice of an effective telescope for viewing it, a 10-inch to 12-inch Dobsonian.

Why a Dobsonian? To begin, in this aperture, 10 – 12-inches, a Dobsonian is the most economical choice. Sure, there are a few expensive custom-made Dobs available in this aperture range, but they are far outnumbered by the inexpensive Dobbies of Synta and GSO. Is a Synta or GSO mirror the equal of a Zambuto? No, but the current imported mirrors are actually very good. It’s unusual to find one with a figure that’s not at least ¼-wave and often better, and one will serve well for deep sky observing (and may not be a slouch on the planets either). A 10-inch GSO or Synta Dobsonian can be had for around 500 dollars and is an incredible bargain.

At least as important as cost, for me anyway, is portability. A 10-inch or 12-inch fork mount SCT is a heavy telescope any way you slice it. A 12-inch Meade is frankly a beast best suited for an observatory. A 10 or 12-inch SCT OTA on a separate mount is easier to handle, if not that easy, but then you have to transport and set up a GEM (or other) mount too. I don’t mind doing that occasionally, but certainly not for an hour long Messier run from my backyard.

In contrast, a 10-inch solid tube Dob is easy and quick for most adults to transport and setup. The OTA will fit in the backseat of most vehicles, and all there is to assembling a solid tube scope is “plunk rocker box down, place tube in rocker.” This degree of portability does begin to ebb at 12-inches, admittedly. Carrying a 12-inch solid tube Dobsonian is doable for some people, but it is like wrestling with a water heater. Luckily there are alternatives.

One is the traditional truss tube scope. That is a good solution if one can be left assembled for transport to the backyard. Often that is not possible, not with the trad style truss scope. The tube assembly can be even more awkward and heavy than a solid tube telescope. And disassembling the tube to get the scope into the backyard and then reassembling it is a pain.

However, there are now 12-inch Dobsonians that are easier to handle than old-fashioned trusses and somewhat lighter than a solid tube telescope. I’m talking about the collapsible tube telescopes from Synta. Another possibility if you have considerably more bucks to spend is the ultra-light Dobsonians, which are available from several makers.

A Dob is a good choice for attacking M51 or any other Messier, but it’s one that leaves some beginners uneasy:  “Don’t I need goto and tracking?” Both those things can enhance your experience, but goto/tracking is no longer the exclusive province of SCTs. Synta produces Dobsonian telescopes under its SkyWatcher brand and for sale by Orion that feature both things. And an un-driven scope can be equipped with digital setting circles that make finding easy. Isn’t it hard to track an object by hand at higher powers? Not if the telescope is properly made. I find tracking at 500x easy with my 10-inch GSO Dobbie.

None of this is to say you must have at least a 10-inch telescope to have fun with M51. A dark sky can allow much smaller scopes to do a good job on the galaxy and its companion. My experience, however, is that 10-inches is where it starts getting really good.

OK, let’s go, beginning with M50…

M50, the Heart Shaped Cluster

Do you like open clusters? You don’t? OK, OK, but this is a Messier open cluster and at least somewhat removed from the “dim, not well detached” NGC opens that provoke your scorn. M50 is bright at magnitude 5.9 and reasonably compact at 15.0’ across its longest dimension. It’s visible easily in finders and quite rewarding in medium aperture telescopes.

Since the cluster is easy in a finder, locating it is trivial on those deliciously dark and clear winter evenings after a front passage. Scan some 5-degrees northeast of Theta Canis Majoris, the big dog’s “nose” star, and you should run across M50 without a fuss. This is a fairly star-rich area, but M50 is the only open cluster of any prominence in the region.

On target, your reaction will likely be much like mine, “Not too shabby, not too shabby.” A 10-inch will show maybe 25 bright stars and perhaps three times that many fainter ones at medium magnification. This is the Heart Shaped Cluster because its looping star chains seem to outline a Valentine’s Day heart. I sometimes have trouble making out the supposed “shapes” of open clusters, but even I see a heart here. Look for the prominent red central star in the midst of M50’s suns.

M51, the Whirlpool Galaxy

M51
And here we are at the Whirlpool. What do you need to know about it most of all? That it is beautiful, but also subtle. Its magnitude is 8.1 and its size is 11’12” x 6’54”, yielding a surface brightness of somewhere around 13, which doesn’t sound too bad, but remember you are after details, and those details, the spiral arms, the dust lanes, the “bridge” between it and its interacting companion galaxy, NGC 5195, are not easy. Sure, I’ve seen the galaxy from heavy light pollution, but only as two blobs, a bigger one and a smaller one, and most of us want the Whirlpool to be more than a “been there” object.

To do anything with M51, you have to get there, of course, and without a goto computer and in a moderately light polluted sky, that can be somewhat difficult. What works for me is a 50mm finder and a pair of 7th magnitude stars that lie 3-degrees 21’ northwest of bright Alkaid, the “end” star of the Big Dipper’s handle. M51 is just 19’ farther to the northwest and closest to the southeastern star of the pair. If you are observing from the suburbs, pay close attention to the field. M51 will not likely jump out at you.

So what will you see with a 10 – 12-inch telescope? That depends. From my club’s (semi) dark site in the suburban-rural transition zone, I can always make out spiral structure with the 10-incher, but, remember, I’ve been looking at this thing for nearly 50 years. If you are new to the Whirlpool, spend plenty of time on it, use a variety of magnifications, and employ the tricks—like averted vision--we discussed a while back. Beyond basic spiral structure? I can usually see parts of the bridge of material between the two galaxies, but it is not complete. I can also, on a good night, a superior night, see hints of the Whirlpool’s convoluted dust lanes.

M52 and the Bubble...
With a larger telescope, you will see more from a site like my club’s, but not a whole lot more. What this galaxy, like most galaxies, needs is a dark sky. The best view I’ve ever had of this object was with a modest instrument, my old 12-inch telescope, but that scope, Old Betsy, was sited under the very dark skies of the Texas Star Party in 1999. From there, the complete bridge was obvious (if still not blinding), and I wasn’t just able to see dust/dark lanes, I could see their edges were not smooth, but “curdled.”

M52, the Salt and Pepper Cluster

Cassiopeia’s M52, another open cluster, is not good and it’s not bad. What makes it stand out is a superb neighborhood. While a 10-inch is once again probably optimum, even a 4-inch will do a good job of capturing this magnitude 6.9, 16.0’ group.

Look for M52 about halfway along and 45’ west of a line drawn between Beta Cassiopeiae, Caph, and Iota Cephei. While not as prominent in a finder as M50, you should still be able to see something here with a 50mm.

M52’s main claim to fame—if any—is its legion of tiny stars; up to 100 are visible in medium aperture telescopes at medium-high magnifications. There’s a red central star, but the chief impression is “tiny, closely-packed stars,” which is what gives the effect of a sprinkling of salt and pepper on a dark background.

The neighborhood I mentioned? If you’ve a dark enough sky and a 10 – 12-inch telescope and maybe a nebula filter, move your telescope 36.0’ to the west and you will come upon the famous Bubble Nebula. While it is easy to image, it’s not quite so easy to see any of the nebulosity visually, much less the bubble shape, without dark skies and good transparency.

M53

M53
M53 has, to me, always been a herald, a herald of the return of the summer sky and its hordes of globular star clusters. This spring glob is not nearly as good as its more easterly mate, M3,  but after a months of a globular shortage I welcome it, and it is pretty good. Better than puny little M79 anyway. In a dark sky and riding high, this magnitude 7.7, 13.0’ across ball of suns is pretty in a 10-inch or an 8-inch if not overwhelmingly pretty.

For once, finding is not a concern. If your site is at least good enough to show Coma Berenices’ magnitude 4.3 Alpha star, Diadem, you are in like Flynn. M53 lies a mere degree and a half to the east. On a decent night, the cluster should appear as a slightly fuzzy “star” in a 50mm finder.

When you are there, what will you see? From the average suburban backyard, all you’ll find in the eyepiece of your 6-inch and smaller scope is a fuzzball. A prominent enough fuzzball, but a fuzzball. An 8-inch will give you a cluster that wants to break into stars, but can’t quite do it. Grainy, yes, resolved, no. In 10-inch and larger telescopes, you get what you came for: plenty of tiny sparklers.

If you have really good skies and an 8-inch or larger scope at your disposal, look for M53's companion globular NGC 5053, which is loose and difficult. This open cluster-looking glob lies about a degree southeast of M53.

M54

Here’s another glob, Sagittarius' M54. At magnitude 7.7 and a size of 12.0’, this one is hardly a spectacle. That’s largely thanks to the relatively large distance between us and this fairly compressed (Type III) star-ball. It’s some 36,000 parsecs distant and looks it.

Luckily, finding M54 is trivial if Sagittarius is decently high in your sky. It is found on the “handle” side of the Teapot’s base and is 1-degree 42’ west of Ascella, the teapot’s “leftmost” bottom star. Tread carefully, especially if your location is at a higher northern latitude. In horizon haze M54 will definitely not be prominent.

What it will be is a fuzzball. Not just in 4 – 6-inch telescopes, but in 10 – 12-inchers as well. As above, it is tight and far away, and while it begins to look grainy in 12-inch scopes, I’ve never achieved much resolution in even a 16-inch under suburban skies.

M55

M55
This is yet another Sagittarius globular. Alas, it’s no M22, though it might look quite a lot like that fantastic glob if it weren’t so poorly placed for Northern Hemisphere observers. As it is, this magnitude 7.42, 19.0’ group is sadly diminished.

M55 can also be difficult to find “manually.” That’s because much of the time it is in the treetops and it is also located in the rarely visited southern portion of Sagittarius well removed from the teapot. Position your telescope 8-degrees southeast of Ascella, and scan carefully with as low power an eyepiece as you can use given the probable brightness of the sky background in this part of the constellation. M55 is a loose one, a Type II, so look for something that appears to be a round and rich open cluster.

The actual appearance of M55 will depend on how high it is in your sky, the transparency in its area, and the aperture of your telescope. This is really an object for a 10-inch at least, and on a good night down here in the southland, many teeny stars are revealed in M55. It ain’t exactly a spectacle, but it’s worth your time under the right conditions.

M56

Yes, there are Messier globular star clusters and then there are Messier globular star clusters. M56 is most assuredly not an M13. Or even an M30 or M53, though the cluster’s specs don’t sound that scary. It shines out at magnitude 8.4 from its lair in Lyra and spans a mere 8’48” of space. The problem is that it’s a Shapley Sawyer Type X. A XII is the loosest type, so M56 is much like NGC 5053, if not quite that bad—5053 is an even looser XI and is considerably dimmer.

M56
But, yes, M56 can be tough; it was amazingly so for me when I hunted it one long ago night from my parents’ suburban backyard with my 4.25-inch Palomar Junior reflector. It was a Messier globular and Lyra was riding high. Ought to be duck soup, right? I got the scope on the cluster’s approximate position with the aid of Norton’s Star Atlas. Nothing. Nowhere. Could my aim be that far off? No. I finally spotted the little devil as a dim, very dim, round glow. That was M56?

It’s easy to get on M56’s spot without a computerized telescope as it is conveniently placed approximately halfway along a line drawn between Albireo and Lyra’s Gamma star, Sulafat. It’s actually a little bit outside that line to the east by about 45’ and slightly closer to Albireo than Sulafat. If you need further direction, a fairly prominent magnitude 6 star, SAO 68040, is 24’ northwest of the cluster.

What do you get for your efforts? From the average backyard, not much; in a 6-inch, M56 remains a smudge not much better than what I saw in the Pal Junior.  An 8-inch will begin to resolve a sprinkling of stars at about 150x, but still “mostly a round glow.” Things get better in Zelda, my 10, which, when I increase the power to 200x, begins to bring home something that looks like a globular. To get more than that the solution is a dark site.

With (now sold) Old Betsy, M56 was quite attractive from darker skies like the Percy Quin State Park of the 1990s, the initial home of the Deep South Regional Star gaze. Under those good but hardly perfect conditions, the cluster began to at least approach M53. In addition to plenty of resolved stars in the outer halo, the 12-inch would show M56 has a distinct, brighter, triangle shaped core.

How did you do? What did you see? How did you see it? I’d love to hear if you’d like to post your comments. I am not able to respond to every single one, but I assure you I do read them all. 

Comments:
Rod:

Just a question for you. I've had a LXD75 for about six years, but now have extra funds to up grade to an AVX. The only astronomy I am doing now is using a feature of one of my cameras to see in real time (30 second exposures showing on the screen as you take them). I am think that using the additional alignment procedures in the AVX would give me better alignment.I would be mounting my C8 (same one you told me to buy on Sci.Astro.Am or whatever it was called) and small camera on it. Thanks.
 
Is the VX somewhat better than the LXD75? Yes. Will AllStar produce a better polar alignment than the 75's polar scope? Yes. Like night and day? No.
 
thank you Rod, Will just wait until the LXD dies then.
 
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