Sunday, November 13, 2016
Issue #517: Beginning the Messier Homestretch
The 2016 Deep South Star Gaze is now done, and with it my star partying for the year. And after weeks of unbelievably dry conditions and mostly clear skies, the clouds and rain are back. That means it’s time to continue my detailed observing guide to the Messier objects, starting with a good one.
We begin with Hercules’ other globular cluster, M92. I didn’t spend much time with this star cluster as a youth, not because it wasn’t good, but because, as everybody points out, it is much overshadowed by nearby M13, which I tended to obsess over. I spent my summer evenings in Hercules trying to somehow, some way coax a little resolution out of the Great Globular with my puny Palomar Junior Newtonian.
While Messier 92 is a nice object, it is in no way a first rank globular as some pundits claim. Even if M13 were not in the same constellation stealing its thunder, it still would still be considered an also ran. It is not an M13, but it is also not an M5, an M3 an M2 an M15 or an M22. It’s better than M30 and M53, but is definitely a second-string Messier glob.
Which doesn’t mean M92 doesn’t look stupendous under the proper conditions. At a dark site, this Shapley-Sawyer Class IV globular is busted into hordes of pinpoints by a 6 or 8-inch telescope, and in a 10-inch it begins to make you think it really is competition for the top globs—well until you slew over to M22, that is. Still, at magnitude 6.4 and 14.0’ across M92 is, yes, a showpiece.
Alrighty, then, let’s have a look. If you, like me, use non-goto, non-DSC equipped telescopes at least some of the time, rest assured this one will not cause any object-locating heartburn. To find it with my Rigel Quick Finder equipped 10-inch dobbie, Zelda, I insert a medium-low power eyepiece and position the bullseye on a spot in space that forms a near 90-degree triangle with Eta and Pi Hercules. Our target lies 6-degrees north of Pi and is bright enough that just a little slewing around always turns it up after I position the telescope in its approximate location.
What’s it like in the eyepiece? In my backyard, my 3 – 4-inch refractors can make it look grainy, even on somewhat poor evenings. I was out just the other night with my 3-inch f/11 SkyWatcher refractor, and marveled that not only was M92 easy to find on a hazy evening, but that it looked like a globular. While not resolved, it wasn’t just a smudge, either.
As with most globs, every increase in aperture makes the cluster better, but this one, second-string though it may be, doesn’t require a large scope to look terrific, as I found out one night at the club dark site with my ETX125, a 5-inch MCT: “The core looks almost square at 170x. The outer region is round and populated by many, many stars, some of which hold steady with direct vision, and some of which tend to wink in and out.”
|M93 sketched with my Pal Jr...|
Winter is open cluster time, and one of the better winter galactics is magnificent M93 lurking in oft-ignored constellation, Puppis. What we have here is a group of about 15 – 20 bright stars and maybe 50 dimmer ones spread over an area of about 20-minutes of arc, In other words: perfect for small scopes. Well, depending on your site, anyway. M93 has a rather southerly declination, -23-degrees 51’, and for many observers that puts it a little close to the horizon some of the time, especially considering its somewhat subdued magnitude, 10.93. It is still worth plenty of eyepiece time, though.
Finding M93 manually is not difficult if you can see the magnitude 3.3 star Xi Puppis. The problem for most of you will be that while you can see this star, “Asmidiske,” which lies some 16-degrees southeast of Sirius, you may not be familiar enough with the stars of Puppis to know which one of the constellation’s scattered suns it is. As I’ve often said, if you want to star-hop efficiently, you have got to familiarize yourself with the less well-known and visited constellations. Once you’ve got Xi in the finder, the cluster can be easily swept up a degree-and-a-half to the west-southwest. Despite its somewhat dim nature, M93 should be visible in a low power eyepiece in the backyard.
I often looked at M93 when I lived in my pre-Chaos Manor South downtown home in the 1980s. For a (short) while, the largest telescopes I owned were 4.25-inch and 6-inch reflectors, and given the rather severe light pollution, open clusters were often about all I could see well. While M93 was sometimes in the trees, it never failed to thrill me. Occasionally, as in the accompanying sketch from those days, all I could see with my 4-inch was the central group of brighter stars, but it still looked great. From a dark site in my modern 4 and 5-inch refractors, this field just comes alive with hordes of small stars.
M94, the Croc’s Eye Galaxy
What’s troubling you, bunky? Your spring backyard sky is hazy and the light pollution is heavy, but you still long to see a galaxy? I’ve got one your small scope can pull out every single time, M94 in Canes Venatici. It’s an Sb spiral with a preternaturally bright center as befits its status as a Seyfert galaxy and which allows it to be visible in 3 – 4-inch telescopes with ease in nasty skies.
|M94 imaged with the old DSI...|
There is absolutely no difficulty involved in finding M94. It is a degree-and-a-half northeast of a line drawn between Canes’ two prominent stars, Cor Caroli (Alpha), and Chara (Beta). Position your scope almost midway between the two hunting dogs—maybe a smidge closer to the Alpha dog—and then slew that 1.5-degrees northeast. The only possible diff is that at low power M94 can resemble a slightly bloated star.
And a slightly bloated star surrounded by some thin haze is all you will see in a small scope from the backyard. Without larger aperture (or a camera) and a dark site, you’ll fail to understand why this object is “the Croc’s Eye.” The reason for that moniker is that in large aperture scopes at high power (or in my in my C8 equipped with Meade’s old DSI camera as here) you begin to see spiral structure surrounding the bright core, which is in turn surrounded by a faint ring (a starburst region). The combination of these things does make this object somewhat resemble a reptile’s eye.
When it comes to spring galaxies from the backyard, we go from the trivially easy to the considerably harder. M95, a magnitude 10.6, 7.1’ x 4.3’ Sb spiral is not impossible, but at times it is unavailable to a 4-inch or even a 6-inch under compromised skies. It’s still a nice catch, however, and if you’ve got a 10-inch available you’ll like the field, which includes its sister galaxy, M96, just 42’ to the east.
Finding M95 without electronic assistance is not always easy. The only ready signpost is magnitude 5.45 Kappa Leonis in Leo the Lion’s “belly” area. The galaxy lies 2-degrees 33’ to the south. A better way to go might be to find the much more prominent galaxy M105 first. From there it’s a trip of only 1-degree 17’ to the southwest to get on the M95 field.
Once there, don’t expect too much if you don’t have dark skies. Even in my 11-inch SCT, M95 was subdued in suburbia: “Like M96, M95 is basically a round fuzzball in light pollution. Stellar core. It is slightly easier than M96.TeleVue Panoptic 22mm, 127x.” Frankly, even under dark skies with larger scopes, don’t expect much else.
M96 is M95’s companion galaxy, and is similar visually to M95. While it’s somewhat brighter at magnitude 10.1, it is also a little larger 7.6’ x 5.0’, and actually slightly less prominent to my eye. Like M95, it cries out for 10-inches of aperture in the average backyard if you want to make things easy. Which doesn’t mean you can’t spot it with a smaller instrument on a good evening. I’ve seen both it and its neighbor with my C102 refractor on haze-free spring nights.
If you’ve found M95, you’ve found M96. Just remember: M96 is on the east, and M95 is on the west.
|ATIK Infinity M97...|
What can you see once you are there? In 8-inch – 10-inch instruments, you’ll see a somewhat elongated fuzzy, maybe 2’ worth, with a brighter center. In larger scopes at better sites, the galaxy increases in size but still doesn’t give up much more in the way of detail.
M97, the famous Owl (planetary) Nebula in Ursa Major has, as I’ve said before, a reputation for toughness. That’s an undeserved reputation in this day of OIII filters, which can make old Owley pop out of some pretty bright skies. But you know what? I’ve spotted it with a suburban 3-inch without a filter. Oh, it was much better with the filter than without it, but it was nevertheless detectible sans LPR filter. With an OIII? My 60mm ETX has pulled it out of remarkably putrid skies.
It’s no hassle to find the Owl the old-fashioned way, as it lies only 2-degrees 20’ east-southeast of a prominent star, magnitude 2.3 Merak in the bowl of the dipper. Put a filter on a 25mm eyepiece, scan in that direction, and the large (3’24” x 3’18”) round glow (magnitude 9.9) of the Owl will enter your eyepiece.
There, in a small scope, that’s about it: a round smudge. A larger telescope, a 10 - 12-inch may, may reveal the holy grail of owl-watcher, the two dark spots that are its eyes and which are the reason this nebula is the “Owl.” In suburban skies, they are most often only suspected in these medium-sized scopes. At a dark site, they are considerably easier, if not always easy. Large aperture telescopes under excellent conditions may also reveal the several 16th magnitude range stars involved in the nebula.
We end on another spring object, a galaxy, M98 in Coma Berenices, which lies on the edge of the great mass Virgo of galaxies. How much you will like this magnitude 10.14, 9’48” x 2’48” edge-on Sab island universe depends, as it usually does with galaxies, upon your aperture and your skies.
From the suburbs, it can be visible as an elongated something in an 8-inch. A 10-inch begins to bring out its edge-on galaxy nature, but you need to get out where it is dark to really appreciate this one.
When you are on the galaxy, I hope you are on it at your club dark site. There, in a 10 – 12-inch, or, better, a 16-inch, M98 can be spectacular, a long, luminous spindle with a bright and tiny nucleus floating in the black void.
And so, we end it for this time with only two more installments to go. Given the way the skies look at the moment—the November storms are on their way—it appears you may actually get one of those installments next week. I have the EQ-6 mount and a refractor set up in the backyard right now in hopes of bringing you something different, but the weather gods clearly say “no.”
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