Sunday, April 20, 2014
My Favorite Fuzzies: M51
Your old Uncle Rod is hoping the weather is changing for the better as spring comes in, muchachos. But it dang sure ain't yet. There’s a big Moon in the sky, and the clouds are still hanging in—usually the suckers taunt me by clearing out for the full Moon. Lunar eclipse? Fuhgeddaboutit. Not only was there not a single break in the overcast Monday night, it rained torrentially. I haven’t been able to continue my Destination Moon lunar imaging program. Much less shoot Mars. Or even do the spectra of a bright star or three with RSpec.
I am for sure hoping for better weather for next week’s Deep South Regional Star Gaze Spring Scrimmage star party. As you might expect, the weatherman is not predicting smooth sailing for the event, but Unk is still hoping. Anyhow, till I can get out and actually do some observing (with the new Mallincam Micro, I hope), here’s another entry in my “best DSOs” series…
Your first look at a deep sky object is usually memorable—if not always in a good way. There are those fuzzies that disappoint badly, like M101 disappointed me the first time I saw it—or, more properly, didn’t see it—in my Palomar Junior. Then there are those that blow you freaking away on night one, the M13s and M42s. Most, however, fall into category three: “Yeah…OK…that’s it?” In other words, not great, not bad. There, but Just OK. Like the Whirlpool Galaxy, Messier 51, in a light polluted sky.
As I’ve told y’all before, my favorite activity when I was a proto-amateur, a ten-year-old kid wishing and hoping for a telescope, was mooning over deep sky pictures in the few “space books” I owned, Stars and a one or two others. The few in the Kate Sheppard Elementary School library. The even fewer in the bookmobile that pulled up at the filling station down the road every other week.
My fave, or course, was M101, the Pinwheel. A close second, howsomeever, and maybe actually prettier, was M51, the Whirlpool. While M101 looked a little more like what little Rod thought a galaxy should look like, M51 had a small companion galaxy, NGC 5195, and the Whirlpool’s spiral arms, I thought, looked more even distinct than the Pinwheel’s—in pictures, anyhow.
|My Pal (left)...|
It was a good thing I’d failed at hunting for M101 with my Palomar Junior before I went after M51. That lessened my shock and disappointment considerably. Before we get to how the Whirlpool Galaxy looked in my humble scope’s 1-inch Kellner and ½-inch Ramsden eyepieces (no silly little millimeters for us back then), though, let’s get the skinny, the stats, the straight poop on this great galaxy.
M51 is one of those Messiers that were actually discovered by ol’ Chuck himself. Charles Messier, out hunting comets one cool Paris evening in October of 1773, ran across one of his prototypal “nebulae without stars” in the small constellation Canes Venatici. He noted this non-comet was very difficult to see in his 3.5-inch refractor. Not only did he have a hard time seeing the Whirlpool, he couldn’t see NGC 5195 at all. Discovering that fell to his BFF, Pierre Méchain, in March of 1781.
What was M51, anyway? Nobody knew. Not till the early years of the 20th century did we learn that it was a galaxy, an “island Universe” just like the Milky Way, albeit smaller, thanks to the work of Edwin Hubble and the other giants of those years. The man who set us on the road to figuring out M51, however, was William Parsons, Lord Rosse, who, in 1845, was the first person to see M51 as something other than a round “double nebula.”
Actually, Sir William Herschel’s son John had seen something beyond the round fuzz-balls other observers recorded when he observed M51 with one of his large telescopes. John couldn’t quite see what the hell was going on, however. His drawing shows M51’s center surrounded by a ring-like structure.
It took Parsons a couple of tries before he was sure he was seeing a spiral pattern in the galaxy. Even with his massive 72-inch Dobsonian-style reflector at Birr Castle in Ireland. Maybe because he was in Ireland with its uncooperative skies. Or maybe because he had no way of knowing what he ought to be seeing.
|John Herschel's M51...|
Anyhoo, on an exceptional April night in 1845, Parsons was able to observe the galaxy’s spiral arms, and subsequently made drawings and painting that don’t look much different from the sketches amateurs make today. After his observation, other astronomers began to see M51’s spiral with smaller instruments—once you know what’s there to see, it’s much easier to see it. Incidentally, Parsons apparently never referred to the galaxy as the “Whirlpool,” and it’s not clear who gave it that nickname.
In the following decade or two, astronomers began to see spiral form in many dim nebulae, failed to resolve those nebulae into stars no matter how hard they tried, the term “spiral nebulae” was coined, and astronomy was set on the path to unlocking one of the big secrets of the cosmos.
“That’s cool, Unk, but what’s the Whirlpool like in a scope? How big, how bright?” Well, Skeezix, M51 is a Hubble type Sbc near face on spiral galaxy. In other words, it is a spiral galaxy with arms that are neither tightly nor loosely wrapped, and which is oriented close to edge-on, so we get a nearly perfect view of its disk. While it is relatively bright at magnitude 8.7, it’s also relatively large at 9.8’ x 7.8’, so, as is the case with all face-on spirals, its light is badly spread out. How bad? Center a magnitude 9 star in your eyepiece and defocus until it’s 10’ across. That bad. It is, however, visible in a small telescope, even a Palomar Junior, even from light polluted suburban skies.
What did M51 look like with the PJ from Mama and Daddy’s backyard in the 1960s? Or with a 6-inch Newtonian from a house not far from Possum Swamp’s shopping mall in the 1980s? Not much, friends, not much. But not bad either. It was not a complete failure like M101, at least.
From any scope sited in light polluted skies, you can only expect so much. M51 is not overly hard to locate, but is not overly easy to find, either. Its position three-and-a-half degrees south of the “tail” star of Ursa Major (the last star in the Dipper’s handle) is not difficult to get on, but if you are not careful and don’t use a medium powered eyepiece to spread out the sky glow, you are liable to pass right over it. Especially if you are used to seeing the galaxy from dark locations or, like Unk when he was a sprout, know if only from its pretty pictures in books. You will be expecting something bright or at least something immediately obvious in the field. It may not be. It may be visible at 50x- 75x, but maybe not. You may have to play the balancing act with M51.
|The Leviathan of Parsonstown...|
Balancing act? Yep. The Whirlpool is large, about 10-minutes across. Actually, a little more than that when you include its buddy, NGC 5195. So, you’ll need an eyepiece field at least 20’ – 30’ in diameter to take in the whole object and leave plenty of dark space around it to provide contrast. You’ll also want an eyepiece that will provide high enough power—I like about 150X—to spread out and thin out the background sky glow. My fave M51 eyepiece used to be the venerable 12mm Type 2 Nagler when I went after the Whirlpool with a C8.
The wonderful thing? You can get all the performance of a Nagler II today for far less than what I paid. Explore Scientific will sell you an 11mm 82-degree field eyepiece for freaking 172 dineros—considerably cheaper than the Nagler was in 1994. I’ve tried the ES 82s in the field, and while I’ve been spoiled by today’s 100-degree AFOV wonders, the ES 82 could be a real sweet M51 eyepiece.
“What the frak did you see, Unk, what did you see?” On an average night in the city or deep suburbs with a 4, 6, or 8-inch, what I saw and still see is the same thing early observers saw, a pair of blobs, a double nebula, the bright centers of the two galaxies. That was at least something, and it didn’t threaten to crush little Rod’s spirit like his continual failure with M101 did. At least I was seeing the millions-of-light-years-away marvel that was the Whirlpool Galaxy, and my imagination could fill in the blanks.
On the very best nights in the city, I can also make out a faint haze, a very faint nebulous haze, around the bigger blob that is M51, haze that represents the disk of the galaxy. On one particularly cooperative early spring night when I was doing the observing for my book, The Urban Astronomer’s Guide, my 8-inch f/5 Synta Newtonian began to show the very vaguest hints of spiral structure. But it was not easy, not easy at all. It took at least half an hour of staring at the galaxy with a dark piece of cloth draped over my head to exclude ambient light before I could reliably see a trace of dark lane detail.
Want to kick it up a notch? Get out of town. At least as far as what is called the “suburban – country transition zone,” which, twenty something years ago, was, for Unk, a spot near Hurley, Mississippi not far from the Alabama – Mississippi state line. That was the old Possum Swamp Astronomical Society Dark Site, and it was not too bad. Not till the dadgum gambling casinos were built along the Mississippi Gulf Coast and began shining spotlights and lasers up into the sky and burning millions of parking lot lights all night long.
Me and my buddy Pat and one or two other PSAS stalwarts would gather at “Hurley” on dark Saturday nights for our deep sky runs. Just like today, Unk could be found out there on evenings when any sensible person would stay home due to weather. And, then as now, despite being younger and stronger and armed with a Walther PPK, I would get spooked by Mothman and The Little Grey Dudes from Zeta Reticuli when I was all by my lonesome.
So what if it was cloudy? Maybe it would clear. This was a year or so before I met Miss Dorothy and, being recently divorced, I usually didn't have much else to do on a Saturday night anyway. I’d haul my homebrew 6-inch Newt to Hurley and hang out till it was obvious the clouds were there to stay or a twig snap caused by a passing possum (“WHAT WAS THAT?”) conjured up visions of the Deliverance Gang and Unk skedaddled.
Sometimes, however, sometimes very, very occasionally, the weather gods would have mercy on not so old Unk, and throw him a bone. So it was one evening in the spring of ’93. I was between decent scopes, having sold my Super C8 Plus to finance the divorce. I hadn’t saved up enough for a new SCT, and didn't even have the 8-inch f/7 Coulter Odyssey yet, which would be the next scope down the line for me.
The sky was suddenly and unexpectedly cloud-free and the imaginary baddies who’d begun to devil me had shambled and flapped off. What would I look at? I hadn’t had a good view of M51 since I’d moved back to the Gulf Coast from Arkansas, and the galaxy was now out of the Swamp’s light dome as the Dipper began to approach its “pouring out” stage. Truthfully, I didn't expect much. I wasn’t a very happy camper, having had to drop back from 8-inches to 6-inches, but I still knew the skill and perseverance of the person behind the eyepiece is what counts most, so I decided to give the Whirlpool the old college try.
I’d like to tell you I was blown off my feet by M51, but I wasn’t and you won’t be either, not at a fair-good site with a small telescope. It was nothing like it had been with the Orange Tube C8 from the Ozarks. And yet…and yet…as I continued to stare, using a 12mm Vixen Orthoscopic and a 25mm Vixen Kellner, there were the spiral arms. They didn’t put my eye out, and I could not hold them steady, but they were there—once in a while. The nucleus of M51 was a small, and so was that of NGC 5195. What was not there? The “Bridge” of nebulosity that connects M51 and NGC 5195. That is the next stop on the road, the next goal of an M51 pilgrim.
|Deeper DSI M51...|
The Bridge, the trail of dust and gas NGC 5195 has pulled off its big compadre as it recedes into the distance, looks bright in images, but it is not. Not hardly. The only really good visual look I have had at it with any telescope other than Tom Clark’s 42-inch Beast was with my 12-inch Dobsonian, Old Betsy, when Miss Dorothy and I attended the 1999 Texas Star Party.
Despite its location way out west at Prude Ranch in the backyard of Macdonald Observatory, you cannot always count on clear skies for TSP. But you dang sure could in May of 1999. Not only was it clear, it was terribly dry—it hadn’t rained to speak of since the previous November. In my experience, “dry” helps almost as much as “dark” when you are chasing tough objects.
First night of the star party, I had a long list of objects to work, TSP Observing Program Guru John Wagoner’s The Planetary Party. A tough list of umpteen planetary nebulae. I knew I needed to get started on it right away if I was gonna get my pin by the end of the event, but I couldn’t. Not for about an hour after astronomical twilight finally arrived, anyhow.
M51 hooked me. It did blow me off its feet this time, in a way like it never has since. It bounded into the field of the 12mm Nagler, and the more I looked, the more I saw. The nucleus was a tiny, burning point smack in the middle of the galaxy’s round, bright center. Not only was the spiral structure easily visible, the arms were, I could finally see, not smooth, but uneven, curdled-looking along their edges. There were countless clumps of dark and bright material along their lengths.
The big surprise? And not necessarily a good one? I could see the bridge, including with direct vision, but it was not that easy, not even in a 12-inch from Prude Ranch, which should give you some idea of the challenge it is from east of the Mississip. If you can see the connecting arm between M51 and NGC 5195 from your club site, even if it takes a big gun, a 20-inch or larger scope to do it, give yourself a big pat on the back.
What’s the next shrine on the M51 pilgrimage? More details in the two galaxies, like HII regions, and, especially, the tiny galaxies like IC 4278 littered across the field. Some of these far distant sprites, including the Magnitude 14 range 4278, are in range of bigdobs, but with lots of ‘em, like pretty little edge on IC 4277, which is northeast of NGC 5195, you have entered the realm of “very small and very dim,” and it’s time to replace your eye with a camera.
|My reward for doing the Planetary Party...|
For the camera of a fast focal ratio scope, the galaxy and its fellow traveler are extremely bright and, most of all, photogenic, with those lovely spiral arms, the interacting companion, and the wee galaxies scattered across the frame. I was still skeptical, though, when I finally buckled down and learned to CCD.
As you-all know if you’ve read my tales of my imaging misadventures here, my initial CCD camera, an MX516 from Starlight Xpress, turned out to be a big bust and soured me on electronic deep sky imaging for dang near three years. Till one day the good folks at Anacortes Telescope and Wild Bird (the proprietors of Astromart) emailed me with the news that Meade had come out with a new and inexpensive color CCD camera that would be a game changer. Would I like them to reserve a DSI for me? Yep, I reckoned I would. I knew I needed to learn the art of computerized astrophotography, and at the DSI’s reasonable price of about 300 bucks I figured I could afford to give it another try.
The DSI was not without its faults. The program you ran it with, “Envisage,” sure was full featured—it would do everything but cook the grits in the morning—but its rather counter-intuitive user interface made it a nightmare for some folks. Also, the camera’s sensor, a one-shot color 1/3-inch Sony chip, was small and could make goto accuracy and guiding critical.
Not knowing too much about the CCD game despite having played with the MX516 for a while, I didn’t realize I ought to be skeered because of the above, and wasn’t. After a night of playing with the DSI at the PSAS’ old in-town observing site, I got the camera to work and work like crazy. The software took a while to master, but it could be mastered, and it had some real good features—like the ability to take short subframes and stack them into a final image in real time.
|The Earl of Rosse's backyard observatory...|
How about goto and guiding? Goto wasn’t much of a problem. My new CG5 mount was pretty good, even though it was still on the original iteration of the Celestron GEM software in 2005 and lacked the calibration stars that would later make the mount’s goto deadly accurate. When the CG5 missed putting a DSO on the DSI’s chip, I just used “Precise Goto.” The mount would slew to a bright star near the target, I’d center that on the laptop screen, and the CG5 would then move on to its final destination, invariably putting the DSO in the field of the DSI.
What also helped was the Meade f/3.3 reducer I screwed onto the C8’s rear port. At that focal ratio, the field of the camera was just about right for most DSOs, and exposures were gratifyingly short. 20 or 30 stacked 30-second subframes made for a reasonably dense, reasonably noise-free picture. Guiding? We didn't need no stinking guiding. Unguided 30-second exposures were usually good. If the stars weren't always round, they were close to it.
Got M51 on the laptop, focused up with the aid of Envisage’s Magic Eye focus tool, took the dark frames Envisage told me to take, covering the scope’s corrector when the software said to and uncovering it when the dark series was done. I then asked the program to start taking 30-second exposures and to take them till I said “stop.”
What followed was real cool, y’all. As I watched, Envisage took subframes of M51, stacking those that met its quality criteria. Slowly, an image of the Whirlpool began to build up on my monitor, until, after about half an hour, I had a picture that made my jaw drop.
No, my shot of the Whirlpool from that night ain’t worthy of a Jason Ware or a Bob Gendler—not even close. The uncooled camera was understandably noisy, and my processing skills were nonexistent, but that M51 was mine. I took it with my CCD camera. It was in color. It showed all kinds of spiral detail. The Bridge was crazy visible. The faint fingers of nebulosity extending from NGC 5195 were there, and I could even see a couple of them little field galaxies.
I’ve since moved on to far more sophisticated cameras. My SBIG can blow the doors off the humble DSI with its more sensitive and larger monochrome chip. My Mallincams can do about what the DSI could do in half an hour in thirty seconds. I still love that DSI, though, and I still have it. It got me over the CCD imaging hump, and I’ve a mind to drag it out again and do a little picture taking with it this spring and summer, if just for old times’ sake.
Messier 51? It is different from my everyday wonders like M42 and M13 in that I’ve had to work at it over the years to get it to give up its secrets. But it has, muchachos, it has, and it’s been fun unlocking those secrets. It’s a wonder, but a subtle wonder, and sometimes that is the best kind.
Next Time: Spring Scrimmage…