Sunday, May 22, 2016
The Messier VII: The Greatest
Before we get to the Great Nebula, let’s talk about “how.” We’ve talked about why novices (or anybody else) might want to take on the Messier list, and we’ve talked about “what,” as in what sort of telescope to use on these deep sky wonders. Now we will address “how” as in “How do you look at ‘em?” What are some tricks and tips for seeing as much of these legendary objects as possible?
The most important thing you can do to improve the appearance of the Messiers, the galaxies and nebulae especially? Naturally, “get to a dark site.” But what if you don’t have a dark site? Or want to observe more often than on once or twice a month runs at a club dark observing location? You can to some extent darken your backyard sky.
The easiest way to do that is with a trick many novices—and more than a few old hands—don’t know: increase magnification. The problem with seeing dimmer objects from the backyard is one of contrast. There is too little contrast between Messier object and the sky background in the eyepiece. The sky is nearly as bright—or as bright—as the M, and the deep sky object is rendered invisible or nearly so.
How do you fix that? Bump up the magnification. Increasing power spreads out the background skyglow, making it less intense. It will also dim the Messier, but often it still provides increased contrast and improves the view. Sometimes a lot. Experiment with a variety of magnifications on each object, but what you want is a power that dims the background but still leaves sufficient space around the object. If you kick up the power so much that the DSO fills the field, there will, again, be a lack of contrast. There will not be enough dark sky around the object to provide contrast.
Another way to darken the sky is to use Light Pollution Reduction (LPR) filters. I have an in-depth article on the subject of deep sky filters coming up in the August issue of Sky & Telescope, so I will refer you to that. Here, I’ll just say filters can make the difference between seeing and not seeing dimmer nebulae.
The next two tips have to do with physiology of the human eye and brain. The most important of the two is called “averted vision.” You’ll find that when you look off to the side of a faint object, look away from it instead of directly at it, you see dimmer features. That’s because looking off to the side of an object brings the eye’s dim light receptors, the rods, which are located around the retina’s periphery, into play.
At first it may feel odd or awkward to look away from the quarry instead of directly at it, but with a little practice you’ll get used to that. Under some circumstances, averted vision may allow you to see two or even more magnitudes dimmer than looking straight at the target and employing only the eye’s cones, the bright-light color receptors.
Jiggling the scope won’t give as much of a gain as averted vision, but it will still yield some improvement. The human eye-brain has an easier time seeing moving objects than stationary ones. That is probably evolution at work. Being able to see moving objects well—like a stalking leopard—would be a survival mechanism. So, tap the scope tube lightly, introducing some vibration, and you may be able to bring home details that were formerly invisible.
What can improve the performance of your eyes even more, perhaps, than the two previous techniques? Allowing them to become as dark adapted as possible, allowing your eyes’ irises to open up as much as possible. Yes, the sky is bright from the backyard, but if your eyes could obtain some dark adaptation, you would see more. What prevents that isn’t really the bright sky so much as it is ambient light, light from nearby sources. Your porch light, the neighbor’s yard light, etc.
What you want to do is rig up some means of shielding yourself and your telescope from intrusive ambient lights you can’t shut off. You can build light shields to shade the scope—I used to construct muslin covered stage flats for that purpose—or you can go simpler and more portable with a sheet of black cloth. A square of black nylon draped over your head can work wonders. What do you do to retain your night vision when you aren’t at the eyepiece? You could try Orion’s silly-looking red-tinted goggles, but cheaper and perhaps more effective might be an eye-patch from the drug store.
Finally, keep that bad ambient light out of the telescope. Most refractors and catadioptric telescopes have dew shields sufficient to keep ambient light out of the optical system. Newtonians are another matter. Modern fast Newts typically don’t have much tube ahead of the secondary mirror, so rig up a tube extension of black material of some kind—plastic, cardboard, whatever—to keep stray light off the secondary mirror.
Check the rear of a reflector, too. The primary cell may have some openings—a good thing where cool down is concerned—which can admit light reflected up from the ground. Rig up a cardboard baffle you can tape or Velcro over the rear of the tube to keep ambient light out of that end of the OTA when cool down is done.
With this arsenal of observing hints and kinks in hand, let’s tackle the next group…
M42 The Great Nebula
And great it most assuredly is. Along with the top globular star clusters of summer, M13 and M5, this is probably the greatest, most spectacular Messier of them all. This HII region, this emission nebula, shines with an integrated magnitude of 4.0, so, despite a size of at least 1-degree 30’ x 1-degree, it is seriously bright. It is, in fact, easily visible naked eye even in the city as the slightly fuzzy middle star in Orion’s sword.
Finding? Since it's a naked eye object, once you know what that fuzzy star represents you’ve found it. As I discovered when I was a little bitty kid with a 4-inch Palomar Junior Newtonian. I was hoping to get a copy of Norton’s Star Atlas “soon” so I could begin seeing deep sky wonders, but to my delight one cold December night, I found star charts are not needed for all Ms. I got curious about that funny star in Orion’s sword, pointed my little telescope to it, and there—OHMYGOD—was the Orion Nebula in my 1-inch war surplus optics Kellner eyepiece.
I won’t reiterate the descriptions of M42 found in a thousand books. I’ll just point out a couple of particulars I don’t hear much about. Yes, the nebulosity is great. Yes, there’s the Trapezium and the other fascinating stars enwrapped in that nebulosity. But what I tend to look at/for more than those things these days are the dust lanes and the nebula’s color.
Up the magnification and start exploring the area of the “fish’s mouth,” the dark bay in the nebula near M43, the companion nebula. This area is criss-crossed by many brownish (in images, anyway), dusty tendrils, and tracing them out in the eyepiece can be a fascinating pastime.
Color? Oh, yeah, I know the party line, “M42 may occasionally appear faintly green in medium aperture telescopes, and large aperture reflectors can sometimes show brown tinges that represent the nebula’s pinks and reds.” That’s true under normal circumstances, but on special nights, and I am not quite sure exactly what makes some nights special, M42 can literally appear stoplight green. Not faint green, but bright green. In an 8-inch or even smaller telescope.
How about trying Light Pollution Reduction filters on M42? I never use them much on Orion. Even in light polluted backyards it holds up well thanks to its brightness, and I prefer its look without an OIII or UHC filter. One of those may be of use when you are seeking fainter details, however. Start with the UHC.
M43, M42’s little buddy, is a smaller comma-shaped patch of nebulosity surrounding the magnitude 6.75 variable star Nu Orionis. M43 subtends 20.0’ x 15.0’ and glows at magnitude 9.0 (that’s the value usually given, but the central area is brighter than that). Not only is M43 interesting in and of itself; it’s a good indicator of the quality of your sky. If you can make out the comma shape easily in a medium aperture scope, you’ve got a good night ahead of you.
What’s to see here, about 10.0’ northeast of the main Orion Nebula? Quite a bit beyond the nebula’s basic shape. Under good skies with a magnification of 250-300x, there are plenty of details available. This, as above, is the area of dusty clouds, and you’ll see them encroaching on the south-southeastern edge of the nebula. You’ll also see the comma’s edges are wispy and complex and deserving of considerable attention. Like the main nebula, I’ve never thought that an LPR filter of any type improved the appearance of M43.
Ah, yes, the good, old Beehive, one of two Messier open star clusters in Cancer. M44, AKA “Praesepe” (“manger”), is a bright one, glowing with a combined magnitude of 3.10. Alas, it is also a large one, extending 1-degree 10’. That makes it proper fodder for big binoculars or a richest field telescope, not something like an f/10 C8. You need considerably more than 1-degree of field to make this one look good, you need a couple of degrees in order to put some empty space around the cluster’s stars.
If you can see the dim constellation Cancer the Crab, you are in like Flynn when it comes to finding. M44 lies in the middle of the triangle formed by Eta, Gamma, and Delta Cancri. If these stars are difficult to make out, it’s still easy enough to locate the target. Just point the telescope in the general area where the center of Cancer is or should be, and your 50mm finder should reveal the cluster without a fuss. In fact, it’s easy to see naked eye from medium dark sites on transparent evenings. In the olden days, people gauged the weather by the appearance of the Beehive. If it was easy to see, nice days were ahead. If not, storms were coming.
When you are on the correct spot, a 6 – 8-inch RFT will show a loose group of about 40 – 50 suns arranged in a slightly oval shape. 70 – 80mm binoculars will real maybe half that number. To me, M44 always looks slightly yellowish, which is understandable given the group’s fairly advanced age (for a galactic cluster). It is rife with red giants.
Don’t put that RFT or binoculars away. The next one is another big one, M45, the famous Pleiades, the Seven Sisters, the daughters of Atlas. Just about everybody has seen this huge (1-degree 50’) and bright (magnitude 1.2) galactic (open) cluster. Almost all my freshman astronomy students know it, though they usually think what they’ve seen is the Little Dipper thanks to the group’s brighter members forming a slightly squished dipper asterism.
Since you won’t have to hunt M45, you can give this group plenty of telescope time. In my old StarBlast RFT or my even older Short Tube 80 refractor, the Pleiades were simply stunning. Even an 80mm telescope brings in hordes of dimmer suns in addition to the bright sapphires that are visible naked eye. There’s something to be seen here in addition to cluster stars as well: reflection nebulosity.
The nebulosity, which is brightest around the cluster star Merope, thus giving it its name, “The Merope Nebula,” is extensive, but it is also dim in the way that only reflection nebulosity can be. It’s easy to image, as in my picture above, taken with an 80mm APO last autumn, but seeing traces of it visually requires a dark site and good transparency. Even then, it’s hard to be sure whether you’re seeing the nebulosity or not. The time-honored analogy is “baby’s breath on a mirror” and that is true in spades. By the way, the Merope Nebula does not represent the remains of the cloud that formed the star cluster; it’s just an area of dust and gas the group is currently moving through.
Y’all know I love bonus objects, deep sky objects with another deep sky object close at hand. In this case, really close at hand. M46 is a nice enough open cluster, mind you. 50+ stars are visible in an 8-inch as a rich group 20.0’ across shining with a combined magnitude of 6.10. On the other hand, the cluster is in an obscure constellation (for novices), Puppis, and is a smidge low for more northerly observers at a declination of -14. There’s that bonus, though, and that makes M46 over the top wonderful.
First you have to find M46. As always, the most efficacious method is just to punch in M-0-4-6 on the hand control. Can’t do that? It forms a long triangle with Eta Monocerotis and Sirius, and you really won’t need much more guidance than that. Under slightly putrid skies it still shows up as a smudge in a 50mm finder. Just don’t confuse it with M47, which is only 1-degree 20’ to the northwest. If the cluster in the eyepiece has a wide range of star brightnesses, with a couple of really prominent ones, you are on M47, not M46.
The cluster itself is a nice one, a basically round and rich group that can show as many as a hundred stars to a 12-inch telescope. There’s a small range in star brightness, most of them being of magnitudes 7 – 9, and that gives the group a substantial, solid looking form; it is well detached from the background. It’s little NGC 2438 that is the prize here, however.
NGC 2438 is a small, 1’10” planetary nebula that looks like a perfect miniature of the big ring, M57. While it’s somewhat dim at magnitude 11.7, the small diameter keeps it easy for small aperture telescopes. I’ve been able to prise it out with an 80mm refractor at 150x. If you’re having trouble finding it, looks for a funny-looking double star about 5’ north of the clusters center. The double looks funny because the planetary nebula is involved with it.
M47 is good, fine, alright, but to tell you the truth, I’d seldom look at it if it weren’t for nearby M46. It’s an OK, cluster, but just OK. Because of the large brightness range of its stars—there are several magnitude 4 – 5 suns in the field—it just doesn’t look as nice to me as M46. The brightness range makes it appear sparser than it actually is, and it is less rich than M47 to begin with.
If you can locate M46, you can locate M47. In your 50mm finder, it will be the cluster to the northwest, and will look brighter given its magnitude of 4.40 coupled with a modest size of 25.0’. Still not sure? It is the group that appears more resolved in a 50mm finder.
When you are on M47, you’ll note it’s basically shapeless, but that the bright stars at its center form a dipper shaped asterism, sort of like a miniature Pleiades or an M39. The view is similar in 8 to 12-inch telescopes, with about 30 dimmer stars being visible in addition to a dozen or so brighter members.
Hydra’s M48 is similar to M46 in that its stars have a fairly narrow range of brightness. It is somewhat brighter than M46, with an integrated magnitude of 5.8, but is not nearly as rich in my 8-inch. Still, not bad, not bad at all. What most novices will find challenging about this one is not looking at it, but looking for it.
If you don’t have goto or digital setting circles, the best bet is to use a half degree long line of three stars aligned northwest/southeast as a signpost. 1 Hydrae, C Hydrae, and 2 Hydrae are located 4-degrees 15’ northeast of Zeta Monocerotis, are in the magnitude 4.5 – 5.5 range, and stand out well in a finderscope. M48 is 3-degrees 15’ northwest of the three stars, and should show up without a hassle in a 50mm finder.
In the eyepiece, you’ll see a scattered, strongly elongated group of about 30 stars. It would be pretty ho-hum if not for the line of bright(er) members that crosses the center of the group. That line of stars, and a couple of arcs of suns also involved in the cluster at least make it somewhat interesting.
Now for something entirely different to end on, a Virgo galaxy, M49. It is bright and impressive for a galaxy, having a magnitude of 8.3 and a size of 10.0’, just right to be easily scarfed up by a 4-inch or even smaller telescope. No, there’s not a lot of detail to be seen, but it is a galaxy that is easy to run down from the backyard. The only problem is how to run it down.
M49 lies in the galaxy-rich wonderland, the “Realm of the Nebulae” between the arms of Virgo. The only saving grace here is that it lies well to the south of the densest area. There are numerous NGCs nearby but no adjacent bright Messier galaxies to confuse you. Still, it’s not easy the first time you undertake to navigate the Virgo Cluster with finderscope and chart. What I used to do before computers was “galaxy hop.” I’d use a wide-field Erfle or, later, a Nagler eyepiece, start at the Star Vindemiatrix, and literally hop from one galaxy to the next, using them as stepping stones to my destination.
When you are finally there, however you get there, don’t be too disappointed. What will be in the field is something that looks a lot like an unresolved globular cluster. A bright core and a hazy, round outer envelope. The better the sky, the bigger the envelope. This is a Hubble Type E2 galaxy, an elliptical galaxy, so there is simply not much detail beyond that to be seen. There are some nearby small 13th magnitude galaxies that can be visible in 12-inch and larger telescopes, and there are a couple of magnitude 13 range stars close by—nope, sorry, you have not discovered a supernova—but that is it.
And here we are approaching the halfway point in the list already. That is reason enough to put on the brakes. These objects are made to be savored. I won’t dash through them when writing about them, and you shouldn’t dash through them when viewing them, especially for the first time.
Sunday, May 15, 2016
I don’t make a secret of the fact that I don’t do as many star parties as I used to. Oh, I am happy to fly in to the most distant events to give talks to my fellow amateurs in my capacity as an astronomy writer/raconteur, but when it comes to loading my Toyota 4Runner with a ton of gear and driving long distances to dark skies to observe? Not so much anymore.
There are various reasons for the above, including the fact that I can now do deep sky astrophotography from my backyard. And who knows? My current aversion to driving to Timbuktu, often to do nothing more than look at the undersides of clouds, may be a temporary thing. Be that as it may, at this time I prefer to stick close to home.
“Close to home” doesn’t just mean I decline to drive two or more days to get to the Texas Star Party or one of the other big events out west. It means I’ve even cut back on my trips to Chiefland, Florida and the Chiefland Astronomy Village, which is a mere six hours away.
Still, I sometimes want darker skies for imaging or visual work than what my backyard or my club’s fairly decent dark site offer. Luckily, one of my favorite star parties, one of the longest running star parties in the USA, the Deep South Star Gaze (formerly the Deep South Regional Star Gaze), is only three hours from home and has skies that are actually slightly better than those of Chiefland.
It gets better still. While the DSSG has always been held in the fall, for some years we’ve also been doing a less formal spring version, the Deep South Star Gaze Spring Scrimmage. No speakers, no door prizes, just observing. There is a meal plan, however, and the small number of attendees compared to in the fall, 20-30 rather than 100-150, means there’s no problem getting one of the small motel rooms in the site’s, the Feliciana Retreat Center’s, Lodge.
|Set up Thursday afternoon...|
What lights my fire about the Scrimmage is that I get a crack at the summer/late spring objects under dark skies at a location with excellent amenities. That and being able to hang out with my long-time Deep South buddies. I’ve been doing the Spring Scrimmage ever since I retired from my engineering gig, with 2016 being my fourth one.
The only problem with the Scrimmage is the weather in this part of the country in the springtime. Year One, I got one night. Year Two I got one good night and part of another. Year Three,last year, I didn’t get squat. That’s just part of the amateur astronomy game, and I can have a good time under less than good skies, but for once it didn’t seem weather would be a problem. This year, the forecasts were unanimous that we’d have clear skies for all three nights of the event, which would begin on Thursday, May 5th. Yee-hah!
How did I feel about the trip as I loaded up Ms. Van Pelt, the 4Runner, late Wednesday afternoon? I was pumped. It wasn’t just the amazingly beautiful and uncharacteristically cool, crisp, and clear weather either. I was in the mood to do a star party, more in the mood than I’d been in about a year. I worked with a will to get all the astro-stuff in the truck, almost—but not quite—whistling a happy tune.
My current star party rig is my SkyWatcher 120mm Pro ED refractor, Hermione—this would be her first trip to really dark skies—and since I would be imaging, the mount she’d be riding would be my Celestron CGEM. I had the usual ton of other junk to load as well—cables, cameras, gear cases, computer, etc., etc. By the time I was finished, I was more than ready to call it an early night—well, after a glass or two of Merlot and Arrow on the TV.
The only slight bring down was that some business I needed to conduct Saturday (including attending Free Comic Book Day, natch), meant I’d decided to scale the trip back from three nights to two. I’d be onsite Thursday and Friday nights and go home Saturday morning. Actually, that wasn’t really much of a bring down, since lately two nights at an event seems just about right for me.
Thursday morning’s trip to the Feliciana Retreat Center, which is nestled in the backwoods of northeastern Louisiana near Norwood, was uneventful in the extreme. Miss Dorothy normally does not attend this event, so I was by myself and passed the time listening to an audiobook of one of my favorite Stephen King Novels, The Girl Who Loved Tom Gordon. I was just about halfway through the CDs when I drove onto the spacious observing field slightly before twelve p.m.
How was gear set up? Not too bad. I’ve erected my EZ-Up tent canopy more than a few times by myself, and have gotten pretty good at that, but it was still nice when my old friend Walt stopped by to lend a hand. Two of my other long-time Deep South pals, Barry and Ron, had also arrived and were, like me, getting their telescopes put together, said telescopes being, like mine, refractors.
While this was just a small event, sure, I thought it was telling that lens scopes outnumbered everything else by at least two-to-one. I suppose the current incredibly reasonable prices for high quality imported Chinese ED scopes is what is tipping the table back in favor or refractors again.
The CGEM is heavy enough that it is not exactly a pleasure to mount on its tripod, but it isn’t that bad, and when I know I will be able to leave it set up for a couple of days, not having to take it down and cart it home at the end of one evening, it doesn’t seem bad at all. Hermione only weights 11-pounds and easy to get on the CGEM and very steady on it. What really made putting the telescope and tent canopy together more pleasant than usual? Temperatures in the lower 70s, something rare for us in May. I got all the other junk arranged under the EZ-Up and proceeded to the Lodge to get settled in my room.
The Lodge features motel-like rooms that are clean but not exactly spacious. Nevertheless, Center management feels the need to cram a bunk bed AND a single bed into almost every one, and there’s not enough space left over for even a desk on which to put your laptop. The air-conditioners work, but are old and noisy and on their last legs. So, no, not up to the level of even a Days Inn, but a heck of a lot more comfortable and cleaner than the average star party chickie cabin for sure. I bring along a small folding aluminum camp table for the laptop, and I am good for a couple of days.
What the Lodge lacks as far as rooms, it more than makes up for with its beautiful, modern-looking dining area. This part of the Lodge also features workable (if not hyper-speed) wi-fi and is where most folks hang out during the endless days. What’s the biggest pain with a spring star party? The freaking Daylight Savings Time. It’s a long, weary old stretch from afternoon to eight p.m. when you can at least get your telescope aligned. I spent the hours before supper in the dining area Facebooking, Cloudy Nighting, and QRZ.com-ing.
One thing that has made the wait for dark a little easier to take in past years has been lunch. That tends to break up the day a bit. Alas, the last couple of times it’s been two meals a day, breakfast at nine and an early (4 p.m.) supper, so the days do tend to drag badly.
When supper came, I was reminded of one of the best things about DSSG—the food at Feliciana. Thursday’s meal, brisket, was outstanding. No, I didn’t dare eat the mega-carb loaded baked potato casserole, but the excellent brisket and a large salad from the salad bar were more than enough to fortify me for the night to come.
Out on the field as the Sun slowly, ever so slowly, began to sink, I didn’t have a lot to do. I’d already installed the DewBuster heater strips on Herminone’s objective and the 50mm Orion guide scope. All that remained was to position the computer on the observing table under the EZ up, hook cables to it and to the imaging camera, a Canon 400D, and the guide-cam, a QHY 5-LII, and get the mount aligned.
I had an ace up my sleeve in that regard, the Celestron StarSense alignment camera/system. This does a goto alignment on the CGEM without my intervention, and is as accurate, easily, as the best “manual” goto alignment I can do. Even better, the StarSense encourages me to do two iterations of the AllStar polar alignment routine, since I don’t have to redo the time consuming 2+4 goto alignment after each polar alignment. I just tell StarSense to do another automatic goto alignment and twiddle my thumbs while it does.
What’s the StarSense alignment procedure like? I temporarily remove the guide scope, placing it in my TPI spreader's tray, and mount the StarSense camera in its place. Light off the mount, tell the StarSense HC to do an auto-align, and away she goes. In about three minutes the mount has gone to multiple star fields, has done plate-solves, and I am goto aligned.
After that, if I am imaging, I do an AllStar polar alignment, which works almost the same with the StarSense as with the old hand control. Point at a star, the mount slews off, re-center it with the altitude and azimuth adjusters. The StarSense HC then does another goto alignment and once that’s finished I am done (or if I want the most accurate polar alignment I can get with AllStar, I do another iteration of that followed by another auto-align).
When dark came on Thursday, I remounted the guide scope and focused it by watching the brightness value of a medium bright and non-saturated star increase on the auto-guide program’s, PHD2’s, display on the laptop. By the way, if you have not yet switched from the old PHD to PHD2, you really should. The new version is better.
To focus the main scope I get a bright star, Arcturus Thursday night, as small as I can get it and then sharpen up dimmer background stars by eye. Nebulosity, my camera control program, allows me to focus on a nice big image on the laptop rather than squinting at a tiny picture on the DSLR’s display, and that makes focusing so much easier, y’all. For final tweaking, I engage Neb’s fine-focus mode, clicking on a star on the laptop display, and twitching focus till the FWHM number Nebulosity displays is as small as I can get it.
The rest of the evening was rather anti-climactic. This would be a night of Messier globs, with the first on the list being that gem of spring, Coma’s M3. When the CGEM stopped slewing, M3 was dead in the center of the frame, but I nudged it off center a bit so as to also include a cute little galaxy, NGC 5263, in the picture. Started PHD2 guiding, and after giving it a little while to settle down, I dialed up 180-seconds of exposure with Nebulosity and told the program to acquire 25 subs with the Canon 400D.
After that, there really wasn’t a heck of a lot for me to do. I would check in with Nebulosity and PHD2 occasionally, but my intervention was never required; the software just kept clicking off sub-frames and taking and subtracting darks. I’d brought along a pair of 10x50 binoculars and spent some time scanning the sky. When I tried of that, I checked out my friend Beth’s new 12-inch SkyWatcher collapsible-tube goto Dobsonian. I am glad I downsized to a 10-inch dobbie, but must admit Beth’s scope was delivering impressive images.
So it went for the balance of the evening. I’d choose a new target from the list on my new observing planner program, Deep-Sky Planner 7, switch to my current fave planetarium app, Stellarium, click on the next target, send the mount there with a CTRL-1 key combo, and get another sequence underway. I would then set off wandering the field again. I did take a couple of breaks and walk back to the Lodge for hot coffee. Can you believe it? I forgot to bring along my usual stimulant of choice, Monster Energy Drinks. Oh, well, probably coffee was better for my system than whatever is in the Monsters.
|Pat's new AT130...|
Coffee or no coffee, by just before three a.m. I had had enough. Three targets were in the bag, M3, M5, and M10, and three is my usual nightly goal for long exposure prime focus imaging. I shut everything down, covered the telescope and walked back to the lodge where I watched a DVD on the laptop (the animated Doctor Strange film) until my eyes began to close and I fell into a deep slumber that lasted till somewhat after eight.
Breakfast was at nine, and was the only yucky meal I experienced this spring, or, actually, that I’ve had over the last several years at the FRC. The bacon was good and the biscuits looked terrific (I admired them from afar). The problem was that instead of just doing scrambled eggs, they made a breakfast casserole. The idea was OK, but in addition to eggs, cheese, and sausage, they added in broccoli. Oh, I like broccoli…but for BREAKFAST? Jeezus-pleezus!
After that semi-debacle, I was off to the field to dry everything out. While the dew had not been heavy during the first part of the evening Thursday—in fact it had been amazingly light for Louisiana—the damp had come on as midnight approached, and the observing table was soaked by morning. Six years of exposure to UV at sunny star parties has made the EZ-Up less than waterproof, and it now tends to “rain” under the canopy when dew accumulates on it. I might spray it down with Scotch-Guard, or, more likely, I may just go ahead and replace it with a new EZ-Up. It’s lasted well, but has a few mechanical problems now, too.
With the refractor/mount uncovered to let them dry off in the morning Sun, I set about reconfiguring. My intention for Friday night was to go visual. For one thing, it didn’t look as if the sky would be as transparent as it had been Thursday evening. For another, I wanted to see what Hermione could do visually under dark skies. Finally, stowing the imaging-related cables, the guide scope, the guide camera, etc. would make for a quicker get-away Saturday morning. I definitely wanted to be home by noon to get in line for the free stuff at my LCS (local comic shop).
I also wanted to spend some time observing with my friend Pat’s new refractor. Pat, who planned to arrive Friday afternoon, had recently purchased an AT130 EDT (Astronomics) 130mm triplet ED scope, and I was curious to see how it would compare to my SkyWatcher refractor and to Barry’s pretty TMB 130 set up just down the field from me.
The first part of the day seemed to last forever. I spent some time surfing the Internet and reading (a graphic novel, Neal Adams’ very strange Batman Odyssey). Shortly after noon, I closed my book and trotted back to the field. As I approached, I could see Pat setting up his HEQ-5 mount and preparing to get his new telescope out of her case.
|My traveling companion...|
To say I was impressed by the AT130 would be an understatement. Beautiful, robust white tube. Nice Crayford focuser (rotatable in two places). Exquisite looking objective. The whole package just shouted “quality.” Frankly, what the Astronomics import (China) reminded me a lot of was the William Optics refractors. Pat’s 130 seemed very much the big sister of my Megrez II Fluorite (80mm). The only question in my mind was color correction. The 130 is a triplet, but doesn’t use a fluorite or synthetic fluorite element. It opts for FPL-51 glass instead of FPL-53. How would that stack up?
After the 130 was on her mount, Pat and I spent some time on the field reminiscing about the old days, about the 20 plus years we’ve been doing Deep South together. As we were sitting under my canopy shooting the breeze, Barry stopped by and mentioned his club, the Pontchartrain Astronomical Society, had some stuff to sell, including Telegizmos scope covers at great prices. Specifically, covers for refractors.
That pricked my ears up, since my old Desert Storm Cover simply will not fit over Hermione when she is on a German mount. Barry had two different sizes, including one sufficient for a 6-inch f/8 telescope, which was what I chose so I could use the cover on Big Ethel, my 6-inch achromat, as well. The Telegizmos covers (Pat got one too) seem durable, well thought out, and made it the task of just a few seconds to get the scopes under wraps at the end of the evening. Recommended.
Soon enough, the stars were beginning to wink on. With Hermione being so easy to get aligned thanks to the StarSense, I was able to spend some time helping get Pat squared away with his HEQ-5. He’d had the mount for a while, but for various reasons, including our many months of horrid weather, hadn’t been able to do much with it. In particular, he’d had little chance to play with the mount’s computer and we were anxious to give that a clean bill of health.
Got the mount, which is identical to the Orion Sirius, polar aligned using its polar borescope, and after a couple of false starts we completed a two-star goto alignment—which seemed to work better than a three-star for some reason. When we were done I was impressed at the way the mount put anything we requested in the field of the 130, which was quite steady on the mount.
The true question was about the optical quality of the new AT130 EDT. Again, I was impressed by the telescope. Despite fairly poor seeing, Jupiter showed plenty of detail and contrast was excellent. The same was true with Mars despite the fact that the Angry Red One was low when we looked at it. Certainly the scope provided beautiful wide-field views of deep sky objects.
|The observing field Friday...|
How did it stack up against my SkyWatcher and Barry’s TMB? The views in all three scopes were essentially identical. Were deep sky objects maybe a little brighter in the 130 than in my 120 thanks to those 10 extra millimeters? Maybe, but 10-millimeters isn’t much, and the difference was slight. Color correction on the FPL-51 triplet seemed pretty much the same as on my FPL-53 doublet. One other thing Pat and I concluded? The views he and I were getting were very reminiscent of what you’d expect with a garden variety C8, and both refractors delivered satisfying views of deep sky objects.
How did our scopes hold up against Barry’s high-toned TMB? Very well, thank you. Again, the images in all three seemed more or less indistinguishable to me. Would the TMB have pulled ahead on the planets if the seeing had been better? Maybe, maybe not. It’s amazing how far the Chinese have come in the quality of their ED refractor objectives—simply amazing.
So, I spent Friday night in relaxed fashion playing with our two telescopes and enjoying the planets and the brighter, more spectacular deep sky wonders. I was having a great time and was sad when midnight began to approach and with it the inevitable need to pull that cursed Big Switch. I covered Hermione, returned to the Lodge, and was soon enjoying a few hours of shuteye. But only a few; I’d need to be up again at five in the stinking a.m. to pack.
Saturday was not exactly a treat, but was bearable. I was happy I’d stowed all the astrophoto gear away Friday morning, for sure. Biggest bummer was packing the EZ-Up, which was soaking wet. If Thursday had been slightly damp, Friday was well on its way to being a typical dew-heavy southeastern spring night. I got ‘er done, though, and was on the road by 8:30, just a little later than planned. The end of the Scrimmage for me was not the end of the week’s astronomy fun, however.
|FCBD at FOS Comics...|
After the drive home and FCBD and the other business I had to conduct, I was understandably tired on Saturday evening. BUT… It was obviously going to be another beautiful night under the stars and I didn’t want to waste it sitting inside watching TV. How about a trip to the club darksite then? I wasn’t about to repack Hermione and all her support gear, but that didn’t mean I'd lack telescopic horsepower.
A night like this would be perfect for Zelda, my no-frills no-goto GSO 10-inch Dobsonian. I had her, my Asus Android tablet (running SkySafari), and a box of eyepieces in the 4Runner in no more than 10-minutes and was on the road to the little country airstrip we use for our serious deep sky work.
Onsite, less than 10-minutes elapsed before I had Zelda out of the truck, on the field, and ready to rock. It wasn’t dark quite yet, but was at least dark enough to have a look at Jupiter, who was riding high in the gloaming. It wasn’t just to be an idle look, either; I had an agenda. What I wanted to know was how the Dob’s views would compare to what Pat and I had seen through the refractors.
Verdict? Pretty much a wash. The seeing was no better than it had been the previous two nights, and that no doubt prevented the 10-inch, who has a very good mirror, from pulling ahead. Yes, there were plenty of details when the seeing would settle down a little, and the Great Red Spot was easy to see, but could I see anything I hadn’t seen with the lens-scopes? No. I thought the color of the GRS was a little more saturated than in the refractors, but the difference was not striking.
On the deep sky, on M3 specifically, there was no denying Zelda left the refractors in the dust. Yes, you might say the stars had looked tinier and sharper in the 120 and 130mm scopes, but the 250mm reflector just provided more light and more stars and there was little doubt the view of the globular cluster was “better.” That wasn’t what surprised me, however. What surprised me was how well the refractors’ views of M3 actually held up against those in a much larger telescope.
What else did I look at? Not much. Shortly after astronomical twilight it became crystal clear I needed to get the heck out. Not because of Mothman, the Little Grey Dudes from Zeta Reticuli II, or the Skunk Ape, though. The big baddies who used to haunt me when I was alone at the dark site seem to have lost their power over me. That’s thanks, I suppose, to all the changes I’ve gone through in the past year.
It was the little baddies who chased me home. The mosquitoes. They were fierce, and I’d forgotten the bug spray. In my tired, fuzzy-thinking condition, I’d also forgotten to bring a jump start battery along. I had nothing to power my dew zapper gun, and my finderscope and Rigel Quick Finder would no doubt have dewed up before long.
Sunday passed uneventfully, and I thought Monday would too. Yes, there was to be a spectacular transit of Mercury across the Sun at dawn on that day, but the weathermen were unanimous that we’d have heavy clouds from the event’s start to finish. I went to bed expecting nothing.
Surprise! At dawn a look out the bedroom window revealed the sky was beautifully clear and blue. I dressed in a hurry and grabbed my most portable combo, the SkyWatcher AZ-4 alt-azimuth mount and 80mm SkyWatcher f/11.3 achromatic refractor. Slapped a Thousand Oaks solar filter on the scope and had a look with a 20mm wide-field eyepiece. There was the little bb that was Mercury. Nice, complex sunspot group too. It was quite wonderful to watch the little world’s slow progress across Sol. After Dorothy and I had taken good long looks, I even snapped a few iPhone photos through the eyepiece.
The denouement was that the weather-goobers were eventually proven correct. A couple of hours into the event we were completely clouded out, but I’d seen plenty and was happy and lucky to have seen anything. That made it a twofer for me. We’d caught the inception and the first minutes of the Venus transit in 2012 (but not much more than that thanks to violent thunderstorms) and now Merc. Cool. All in all a very good week astro-wise, and the most active and engaging one I’ve had in a while.
There are many more Scrimmage pictures on my FaceBook page.
Up next? More Messiers, that’s what.
Sunday, May 08, 2016
Spring Scrimmage 2016
Wha? No Blog? That’s right, friends. As usual when your faithful correspondent has been on the road, I am taking a break. You will learn about the events of the just completed Deep South Star Gaze Spring Scrimmage next week (that’s the plan anyhow) though. I have some other interesting articles lined up for the coming weeks as well, including a full report on some new software, Deep-Sky Planner 7, and the next edition of my Messier series. See ya then!
Sunday, May 01, 2016
The Messier VI: The Auriga Trio
How do I feel about wallpaper chasing? "Wallpaper chasing? What the heck is that?" In the ham radio game, that’s what we call the quest for awards. Contacting all 50 states. Working stations in 100 countries. The same thing goes on in amateur astronomy in the form of the Astronomical League’s Observing Clubs (one of the few things that make the League relevant for the average amateur today, I am sorry to say).
Anyhow, I’m not much of an observing award collector, but I do recommend the Messier Club. I never went on to obtain the Herschel 400 or the Herschel II certificates despite having observed all 2500 of those suckers, but I experienced a genuine feeling of accomplishment when I finally applied for and received my Honorary Messier Certificate and pin a couple of decades ago.
The Messier Club comes in two flavors. Observe 70 objects in accordance with the program’s rules and you will get a nice certificate. Do all 110 and you get the Honorary Award, which brings not just an even nicer certificate, but a handsome pin. Again, while I don’t much like chasing observing awards, I did enjoy doing this one. You might too.
Enough of that. Onward! Starting with three of the finest open clusters in the winter, the Auriga Trio, Ms 36, 37, and 38.
I am generally of the opinion that M37 is the best of the Auriga amigos, but M36 is a close second. How could it not be with the specs it has? It’s bright at magnitude 6.0 and also very compact at 10.0’ in diameter. M37 may be richer, but M36 has more bright stars. M37 tends to look like “grains of sugar on black velvet,” while M36 is “diamonds on black velvet.”
What’s it like to find without a computer? Duck soup. It is just about midway along and a degree and a half southeast of the line that connects two of the stars of Auriga’s pentagon, Beta Tauri and Theta Aurigae. Just get your scope in the general vicinity—I do that with my Rigel Quick Finder zero power sight—and you’ll immediately spot M36 in a 50mm finder (which you should have in addition to a zero power “unity” finder).
For your trouble, you get a galactic cluster you’ll find yourself staring at for quite a while even if, like me, you are not much of an open cluster fan. What you’ll see specifically is 30 – 60 Suns depending on the quality of your sky and the aperture of your telescope. For best results, I recommend a wide field eyepiece. A medium power ocular with an apparent field of at least 68 degrees will put plenty of open space around M36 and make it look just great. While the cluster is more or less round in shape, the bright stars and star chains of its central region make that area look somewhat square to me.
No, there is no denying M37 is the most beautiful member of the Auriga Trio. At magnitude 5.6, it is even brighter than M36. While at 15.0’ it is larger than the previous object, it doesn’t look that way. That is because with a very condensed (for a galactic cluster) center about 5.0’ across it almost resembles a loose globular star cluster.
Finding? This one always stymies me for some reason. It shouldn’t, but it does. It is, like M36, almost midway between that line drawn between Beta Tauri and Theta Aurigae (though a little closer to Theta). Unlike M36, however, M36 lies outside Auriga’s pentagon figure. Maybe my problem is that while M37’s combined magnitude is brighter than that of M36, it’s got fewer bright stars and is harder to see in a 50mm finder under compromised skies.
You will eventually get there, and when you do what you see will be glorious in almost any skies and with any telescope. In fact, one of the best views I’ve ever had of M37 came with my 66mm William Optics ED refractor one chilly winter's night in Chiefland, Florida over seven years ago:
I’d be remiss if I didn’t mention how well my even smaller scope, the WO 66SD, did. As ED refractor prices have come down to levels even the cheapskates among us—like Unk—can embrace, I’ve finally made friends with refractors. But mostly for imaging, not visual work, and rarely from dark sites. I’d piggybacked the 66 on the C8 mainly as an aid to spotting some of the [Herschel] 400’s large and undistinguished clusters, and it did yeoman duty there. But it did more. When I had M37 in the C8 and had gawked at it for quite a while, I finally thought to see how it looked in the little feller. In a 16mm Uwan [eyepiece], the huge field was amazing. The multitudinous stars were a glittering hailstorm, and the cluster really did look like a loose globular.
Specific notables? While the stars are, as above, dimmer looking than those of M36, they are legion. Depending on your scope/skies you will make out as many as 100 tiny sparklers. Finally, like many open clusters, M37 features a red central star. In this case, a really, really red one. The effect is, to say the least, “striking.”
|M39 with Stellarium|
M38: The Starfish Cluster
M38 is the weakest of the three Auriga star groups, but there is weak and then there is weak and M38 is still a wonder at magnitude 6.40 and 15.0’ in size. It’s relatively easy to find, too, since, like M36, it shows itself easily in a 50mm finder. Look for it 2-degrees 18’ west of M36.
What’s the most memorable thing about M38? Well, there are plenty of stars, including some fairly bright ones, brighter than most of the M37 crew, maybe about 50 in a medium aperture telescope. That’s not the big deal, though. What is is how they are arranged. Unlike M37’s stars, which form a somewhat shapeless cloud, M38’s suns are arranged in lines and streamers, and in a medium-low power eyepiece make the cluster look, yes, a lot like a cosmic starfish floating in a dark sea.
It’s good that M39 is in the summer sky, since this rather sparse open cluster frankly pales compared to the wondrous galactics of winter. Still, it’s not that bad, is certainly a little better than nearby M29, and I have always sorta liked this 39.0’ across magnitude 4.6 cluster. In fact I’ve liked it a lot and certainly recommend you stop by if you’ve never hunted it down.
Finding M39 the old-fashioned way with chart and finder scope is fairly trivial. The cluster if located a little over 9-degrees northeast of Deneb in the “blank” space between Cygnus and Cepheus. While this is actually a rich area, the cluster is large enough and bright enough that you should be able to make out its triangular shape in your finder scope without much difficulty. If you need further guidance, it forms a shallow triangle with Rho Cygni and 82 Cygni, which are close at hand.
|M41 with Stellarium|
What’s optimum for M39? I like a larger aperture telescope, 10 – 12 inches, to bring out dimmer stars and make the field look richer, but in truth, this one looked just fine from my old downtown stomping ground with the 4.25-inch Palomar Junior. There is no denying it was more impressive one night in the C11, however:
M39 is still a little low in the sky and in the worst of the light pollution to the East. Large, star-spangled beauty that fills the field of the 22mm Panoptic eyepiece. A little better in the 35mm Pan, since that places some space around the cluster. Defined by three bright stars arranged in a triangle shape filled with many, many [dimmer] stars. 30-40 stars visible even in the light pollution.
I hate to be unkind, but M40 is simply bleah. And unless you are on a quest to see ‘em all, can be skipped. You see, it’s not really a deep sky object; it’s a run of the mill double star. Yes, I know double stars are technically deep sky objects, but when most of us think “DSOs,” we think “galaxy-nebula-star cluster.”
Why is this one in the M Catalog? Old Chuck Messier had heard there was a nebula in this spot and had a look at the area of the double star now known as Winnecke 4. He could see there was no nebulosity here, but put the double in his catalog anyway since he’d gone to the trouble to measure it.
If you need/want to see M40, you’ll find it in Ursa Major 17.0’ northeast of magnitude 5.5 70 Ursae Majoris, which is a little over a degree northeast of blazing Megrez. The double is not that bright at about magnitude 9.6, but it is easy enough to see in even a 3-incher as a pair of whitish stars separated by a hair less than 1-minute of arc. A good looking double star if you like double stars (which I do).
M41, Canis Major’s only Messier, is justly famous, but this is not really a great one for telescope users. The good is that this is a bright and flashy object, a magnitude 4.5 open cluster that is routinely visible to the naked eye from a decent observing site when the Big Dog is riding high. The bad is that it is big and not highly concentrated. Its stars are bright, but there are not enough of them to really fill in an area of 39.0’, an area larger than the full moon. Any optical aid will easily turn up M41, which lies 4-degrees almost due south of Sirius.
There, a telescope will reveal a rather shapeless mass of 40 – 50 bright suns. It’s nice enough if you can get the power down and the field size up, but it is really best in giant binoculars. It is quite pretty in my good old Burgess 15x70 binocs, the glasses I’ve used the most over the last dozen years or so. The binoculars reveal a nice sprinkling of sharp little pinpricks. I really ought to try my 25x100s on M41 some night.
And there we’ll stop. A little short this time, but the next Messier is M42, the greatest of them all, and I want to be able to give it the space it deserves and requires—up to and including all or nearly all of the next Messier article.
Next time? “You’ve used Deep-Sky Planner 6 a lot over the past several years. You’ve been through four or five new telescopes with Deep-Sky Planner 6. You think nothing can replace Deep-Sky Planner 6. Then you look in the mailbox and there’s a DVD containing Deep-Sky Planner 7. And you break into your happy dance.”
Sunday, April 24, 2016
The Refractor Way Part 5: Is One for You?
As you have probably noticed if you are a regular here, over the last year I’ve been revamping my telescope lineup (amongst other things). I don’t just mean I’ve been reducing scope head-count, though I have been doing that. I’ve also been developing a radically different take on telescope aperture and, especially, telescope design.
To recap the past year’s minus column, almost unbelievably my much-loved 1994 12.5-inch Dobsonian, Old Betsy, was sold. Also out the door went three freaking C8s including my 1995 Ultima 8, Celeste, who’d been to more star parties with me than even Betsy, I believe. My old-time classic Criterion RV-6 Newtonian also found a new home. Finally, my C11 may go as well.
The pluses, the newcomers? First there was Zelda, a 10-inch Zhumell Dobsonian. After her came Hermione Granger, a beautiful and bewitching SkyWatcher Pro 120ED APO refractor. Finally, there was Big Ethel, a 6-inch achromat of somewhat uncertain parentage (though there’s likely some JOC in her heritage; she looks an awful lot like the old Meade AR refractors).
What was the why and wherefore of all these changes? In Betsy’s case it was guilt. Guilt that she was sitting in my shop (a.k.a. “The Batcave”) unused week after week and month after month. The ground truth was that even though my friend Pat had done a lot to lighten up the old-style truss tube 12.5-inch telescope, she was still more of a handful than I wanted to handle, even for star parties and other special observing runs.
The C8s? I was holding onto three 8-inch Schmidt Cassegrain OTAs because…well…because I could. Honestly, while I’d had the Ultima 8 OTA, Celeste, out a time or two since I bought my Edge 800 C8 in 2013, it was only a time or two, and the other pair of 8s had not been used at all. Why would I? The Edge 800 (“Mrs. Emma Peel”) is the best C8 I have ever owned or used.
Now for the incoming telescopes. My acquisition of Zelda, a GSO 10-inch Dobbie, is easy enough to explain. I like to have a large—well large for moi—scope in the inventory. 95% of the things I want to see/like to look at are just fine in a 4 – 8-inch instrument. But there’s that remaining 5%, which is comprised of dimmer stuff. And sometimes I also want a little more horsepower on the bright objects, horsepower provided by 10 – 12-inches of aperture, which will make Messiers “spectacular.”
“Well, Rod. You’ve got a C11.” That I do, and I tried to make myself start using Big Bertha more than I have over the last four years. I removed her from her old GPS fork mount and put her on a Celestron CGEM. That did help encourage me to get her out a little more, since I no longer had to lift 66-pounds onto a tripod. But only a little more. The switch to the CGEM just didn’t help enough.
Setting up the 11 and the CGEM is still enough work that I rarely undertake it. Since the end of my observing program of a lifetime, The Herschel 2500 Project, which was mostly undertaken with Bertha, she has, like Betsy, sat unused. I haven’t yet worked up the nerve to sell the carbon fiber C11 OTA, but it’s become evident I am probably not going to use her much anymore.
Enter Zelda. As I mentioned last time, 10-inch Chinese Dobsonians are both affordable and manageable. For 500 bucks delivered, I got not just a scope with surprisingly—maybe even amazingly—good optics, I got a couple of usable eyepieces, a cooling fan, a laser collimator, and more. Best of all, I don’t mind setting Zelda up in the backyard on any but my laziest evenings.
Now the hard part. Has your old uncle gone from being Mr. SCT to Mr. Refractor? Let’s get one thing straight: I’ve actually used refractors for a long time, including a pair of spectacular William Optics APOs, an 80mm fluorite job and a 66mm “SD” (ED) baby. There’s also been a 4-inch f/10 achromat, a 4-inch f/6.5 achromat, an 80mm f/11 achromat, and, the ancestor of all of them, the Short Tube 80 who came to live with me in 1999.
But why do I seem to be emphasizing refractors now? Simple, boys and girls: they are just so easy. My 11-pound 120mm APO, for example, is wonderful on the CGEM when I want to do serious imaging. She is fine on the Celestron VX when I am not quite so serious. And she is usable on my uber-portable SkyWatcher AZ-4 alt-azimuth mounting when I am not serious at all, just wanting a quick peek at Jupiter. The light weight of the scope is just the lagniappe on top of her other refractor advantages, like very little cool-down required and no need to even check collimation.
There is still more to it. Not only are the visual looks I get through the 120 very much on a par with what I see in the Edge 800, they have that almost indefinable refractor je ne sais quoi. Yes, some of that “refractor images are so sharp; their stars are so tiny” business is due to their (usually) shorter focal lengths when compared to SCTs. But, in my opinion, refractor images really are sharper. There’s also more contrast compared to an obstructed scope, and refractors’ thermal characteristics really allow them to capitalize on their advantages.
Even more important to me than the visual advantages offered by a refractor, however, are the imaging characteristics of the lens scopes. That’s a big deal for me now, since I am on an astrophotography jag again—hell, I even have an AstroBin account now. There’s no focus shift or mirror flop to worry about and so no need for add-ons or work-arounds to exorcise those SCT gremlins. There’s also the usual short focal length and wide-field character of APOs to consider. In addition to allowing wider imaging vistas, if that is your bag, the smaller amount of millimeters of the average APO makes guiding mucho easier.
Are the images produced by a refractor better, though? Better than those I can get out of my Edge 800? Optically speaking, probably not that much. Deep sky imaging is pretty forgiving of optics anyway. However, the pictures I can turn out with the 120ED are nevertheless better than the ones I can do with the Edge. That’s because of the inherent ease of focusing and guiding the refractor. A refractor is just a dream for me to use for imaging after coming off 35 years of using SCTs for deep sky work.
So, here is the bottom line: I ain’t that old, but I am well into my spring semester, and I expect the ease of use and portability of the refractors (and the 10-inch Dobsonian) means they are likely the telescopes that will see me into Final Exam Week, if you know what I mean. In the amateur astronomy game never say never, but I simply cannot see myself acquiring larger/more difficult telescopes.
Does this mean I am against SCTs now? No, not at all, not hardly. For many, many of you, especially novices, an SCT is still the best telescope. Can’t help but be. While one is not the best scope at anything, one is good at almost anything. And if you don’t know which area of observing interests you most yet, a Schmidt CAT is definitely the telescope for you. Even if it is not always the best telescope for you, it may be the best telescope for you for a long time. I sure had a good long run with the CATs, 37 freaking years if I date the beginning of my transition to lens scopes to about 2013.
Just because a refractor is the telescope most useful for me doesn’t mean it is the most useful telescope for you, however. Let’s see if one is…
A Refractor May be for you If:
You are interested in wide field viewing and imaging. Sure, you can use an f/6.3 focal reducer on your f/10 SCT to open it up a bit, but you are never going to get the wide open spaces delivered by the average f/6 or f/7 APO. Use an eyepiece longer than about 25mm with your reduced SCT and you’ll get severe vignetting.
Certainly, if, like most of us, you live where light pollution is a factor, you won’t get to exploit this refractor strength often—the sky background will just be too bright at low power—but when you can get out to a dark site, you will be terribly impressed at what a four or five inch f/6 will show.
You are more interested in the aesthetic quality of images than in seeing the dimmest, most difficult details. Only you can decide what is more important to you, the pinpoint stars and high contrast of a five inch refractor or the light gathering power of a 10-inch (or larger) SCT or other reflector. Or you can, like me, have the both of best worlds, and keep a low-cost Dob in reserve for those times when you want “deep” more than “pretty.”
Ease of setup is important. Yes, there comes an aperture point where refractors become difficult. That point doesn’t come until 6-inches, however. A 5-inch can provide most of the horsepower of a 6-inch, however, and can be remarkably easy to mount and awfully forgiving of the mount. And as hefty as she is, I’d still rather set up my 6-inch f/8 refractor than my C11.
You like pretty things. Yes, I think my Edge 800 is a very attractive scope, but, c’mon, there’s just something about a refractor out on an observing field pointed up at the sky in the gloaming that spells a-s-t-r-o-n-o-m-y.
You are into imaging the deep sky and are more focused on medium-size/larger objects than smaller galaxies and planetary nebulae. This is where refractors really pull ahead. As above, they are generally much easier to use for picture taking, particularly by beginners, than an SCT (or a Newtonian). And remember: on extended objects more aperture doesn’t get you “brighter,” it merely gets you “bigger.” The required length of an exposure depends only on the f/ratio of the telescope.
A Refractor May Not be for you If:
You are after the dimmest of the dim objects visually. There’s an old saw you will hear repeated frequently in places where hardcore visual deep sky observers gather: “aperture always wins.” There is no denying that is true. All things being equal (they seldom are), you will see more with a larger aperture scope. Chasing PGC galaxies? You want a 20-inch Dobsonian, not a 5-inch refractor.
You are a planetary imager after the highest resolution images you can get. How do you make high resolution planetary images today? You take thousands of short exposure frames in as short a period as possible. For them to be well exposed, you need plenty of light. The most efficacious way to do that is with a 10 – 14-inch SCT.
You are interested in a turn-key telescope. Something that appeals to beginners who are struggling to keep their heads above water in the murky sea of amateur astronomy gear is the modern SCT. You get a good scope on a fork mount with everything included. There are fewer ready-to-go refractor packages being offered. Usually it is a la carte.
Finally, you may be, as I was for many years, an astro-dilettante. If you want to take pictures of Saturn one night, spectrograms of Rigel the next, and chase the Hershel 2500 the following evening, an SCT could be your scope. In fact, I will say an SCT is your scope.
You know what? There’s actually only one way to decide if a refractor is for you: get out and use one. Join your local club if—horrors—you are not a member, and look through the refractors some of your fellow members are sure to have. Then do some long and hard thinking. If you decide on a lens scope after that, I salute you. Come on in; the water’s fine.
Sunday, April 17, 2016
The Messier Gang 5
What’s a good telescope for the Ms? Almost any will do. You can see all these famous objects with a freaking ETX 60, after all, if you have access to dark enough skies. One good choice, however, one that will reveal plenty of details in all the Messiers under good conditions and not cost much money is the ubiquitous Chinese 10-inch Dobsonian reflector. Not only are these scopes inexpensive, they are relatively portable and from a dark site they are powerful performers.
How good is my Zhumell (GSO) 10-inch Dobsonian,Zelda? Even at a dark site she is not quite as good as my old 12.5-inch truss tube Dob, Old Betsy (sold some months ago), was. There is not a world of difference, no, but there is a difference. Take NGC 4631, the Whale Galaxy, a popular destination this time of year. Compared to the 12.5, the 10 shows a little less detail in the main galaxy, and the companion galaxy, “the calf,” is a mite less prominent. Not like night and day, mind you, but I can see more with a 12-inch.
So, all things being equal, Old Betsy was better than Zelda. All things are rarely equal, however, and that is certainly the case here. Betsy had to be disassembled, the truss tubes detached from the mirror box and the upper cage assembly, for transport. Naturally, she then had to be reassembled at the dark site. And then taken apart when the run was over. Also, while Bets did a fairly good job of holding her collimation following disassembly and reassembly, she would always need to be tweaked.
Finally, as y’all know, I am one lazy mutha these days, and even with all the weight-saving measures my friend Pat applied to Betsy during her last baseline upgrade, her mirror box was still on the heavy side. For me.
Zelda? She’s a solid (steel) tubed scope, so the only disassembly that needs to or can be done is removing tube from rocker. Said tube easily fits into the backseat of my Toyota 4Runner, Ms. Lucille Van Pelt, and the Rocker box goes in the cargo area upright. While the tube is not light, it’s not a problem for even your broken down old Uncle, and all I have to do to get the scope ready to go is place tube in rocker. Oh, and check collimation. While I check it every time, however, it rarely needs even minor tweaking thanks to her solid tube nature. Yes, you could get a solid tube 12.5-inch, but don’t do that unless you fancy wrestling with a water heater, Padawans.
Those are not the only good things about Zelda. While Betsy had a very decent (JMI) Crayford focuser, Zelda’s GSO focuser is better; it’s a two-speed and is smooth and easily handles my heaviest two-inch eyepieces. In a way, it’s not a fair comparison, since I bought the JMI back in 1998, and we’ve come a long way price/performance-wise with focusers, but still…
There’s also Zelda’s fan. She came from GSO with a cooling fan installed on the rear cell. At first I wasn’t sure that was needed, but as below I now believe it can be a help, a big help, in achieving superior images even in my mild climate where indoor and outdoor temperature variations even in winter and early spring are rarely extreme.
So, last Saturday night, which promised to be clear, at least for a while, I was impelled to pack Zelda in the truck and head for our club dark site half an hour to the west of the New Manse, out in the Suburban-Country Transition Zone. While, it did not appear conditions would hold, I thought I’d at least be able to scope out a few Ms, if not any of the subjects for this week, and worse come to worst maybe put in some time with Jupiter, who was now riding high.
Setting up Zelda and checking her collimation (still spot on) was the work of maybe 5-minutes and then it was M-time big-time. First was the bright galaxy pair in Ursa Major, M81 and M82. While the poor seeing and haze didn’t make M81’s arms exactly pop out, it still looked good, as did its companion, M82. Biggest surprise? Even in somewhat punk conditions the less well known third member of the group, magnitude 10.6 NGC 3077 was wonderfully prominent.
Next was good, old M51, the Whirlpool galaxy and its little buddy NGC 5195. This was a test of my somewhat atrophied finding skills, I suppose. Especially since I’d left my tablet, which runs SkySafari 4, at home (by mistake, natch). All I had on me was the smaller sized edition of Sky & Telescope’s Pocket Sky Atlas, which is a little tough for my eyes.
Nevertheless, with the aid of Zelda’s zero-power Rigel Quick Finder and her (included) 50mm right-angle-correct-image finder, I soon found I had nothing to dread. With SkySafari it would have been even easier to get the Whirlpool in the eyepiece, but I must admit that for visual it’s nice to forget about computers and batteries sometimes, even my Asus tablet, a very modest and user friendly computer.
Onward! I guess, like riding a bicycle or copying the Morse code, you never really forget how to star-hop. It took about 15-seconds for me to get on M65, M66, and NGC 6628, the famous Leo Trio. I easily beat a VX mount set up near me to the target. Unfortunately, it was still a bit early and the group was still in the Mobile light dome to some extent. Nevertheless, Zelda easily showed the different shapes of M65 and M66 and revealed the third galaxy (barely).
If I beat the go-to rig to M65/66, I really smoked it on M3. Use the Quick Finder to position the scope in approximately the correct area of Coma, take a look in the finder, which showed the cluster as a fuzz-spot, center that spot in the crosshairs, and I was done. One of the benefits of a 50mm finder is that it will show any decently large Messier from any decently dark site. The cluster? It was down in the light dome, but the power of 10-inches of telescope mirror was apparent; M3 was beautifully resolved in the 13mm Ethos eyepiece.
I looked many objects following M3, but as the night began to grow old the haze began to devolve into real clouds, almost bringing on Big Switch Time. Jupiter was in a sucker hole, though, so I spent some time with him. How did he look? OK, but just OK. The seeing was only enough, just barely good enough, to tantalize with fine details coming and going on the giant planet's disk.
As above, I found the scope’s fan helped. Given the night’s steadily falling temperatures, the fan ensured my higher power images were as good as they could be in the messy seeing. Instead of just running the fan for half an hour before beginning the run, I had it on all night and I believe that is the way to go when the temperature is changing much. The fan, mounted on the mirror cell, will go almost forever on its eight AA cell battery pack and doesn’t introduce any obvious vibration, so there is really no reason not to let it run.
So much for the preliminaries; now for the good stuff. Let’s have a look at this installment’s deep sky treats.
Well, I don’t know if I’d exactly define Messier 28 as a treat, but it is an M, and it is an at least interesting object, if not spectacular. Its basic problem? Not that it’s too small and too faint, not with a size of 13.8’ and a magnitude of 6.9. It’s its declination, almost -25 degrees. That puts it down in the trash for many of us much of the time. The fact that it’s fairly compact, a Shapley-Sawyer Type VII, also doesn’t help when you’re trying to resolve it. It’s not that bad for me down here at 30N, but it is certainly no competition for nearby M22.
One thing you will not have to worry about is locating M28 if you don’t have computerized pointing. M28 is a mere degree northwest of bright Lambda Sagitarii, the teapot’s "lid" star. Once you have the glob in your field, what do you get for your troubles however minimal? This is what I got with Big Bertha, my C11 one fair but not great night at the club site:
Interesting little globular that benefits from higher magnification in the C11. At 200x it wants to resolve. But is still basically a gray, round ball with a few stars winking in and out with averted vision.
Messier 29 is a sparse open cluster in Cygnus, a little group shining with a collective magnitude of 7.5 and covering 10.0’ of sky. Under suburban conditions, a 4-inch telescope will reveal maybe 20 stars on a superior night. A larger instrument will show more, but not many more. And yet, and yet… I’ve always liked this cute little sucka. Maybe because its stars are arranged in a distinctive dipper-like pattern, like a miniature M45:
M 29 is immediately identifiable in a 22mm Panoptic eyepiece in the C11. Basically a small dipper asterism with 8 prominent members and perhaps twice that many dimmer ones that might be members of the group. Going to 220x pulls out more a few more stars. Fills about half the field of a 12mm Nagler. This cluster is attractive and stands out well tonight at high power, but it's best at the lower magnifications.
Good one alert! Good one Alert! M30 doesn’t get tremendously high in the sky in the Northern Hemisphere. It’s situated in Capricornus at a declination of -23, but its magnitude of 6.9 coupled with a modest size of 12.0’ means it remains prominent.
I’ve always called this one “the Goat Cluster,” and not because of its location in the Sea Goat. On any passable night with a 6-inch or larger scope, you can see two streams of stars coming off the core that—amazingly—resemble the horns of a goat. While the cluster doesn’t offer tremendous resolution for an 8 - 10-inch telescope, plenty of stars are still resolved. One of my very favorite fall objects.
Good God, what can you say about this awesome thing? It is high in the sky for northern observers and is shining at magnitude 4.3. Unfortunately, it extends a huge 2.6-degrees. That doesn’t harm its brightness; I could often see it naked eye on a clear, dry night from old Chaos Manor South in Mobile’s Garden Historic District downtown. It’s not brightness or lack thereof, but that enormous size that makes “Andromeda” less than impressive in larger telescopes.
What you’ll see in your 8-inch, even at low power, is a bright ball, the central condensation of the galaxy enwrapped in bright haze. Slewing around shows lots more haze, but it admittedly it doesn’t look much like a galaxy. To make it do that, you need wide, wide field. My 80mm APO and my 25x100 binoculars are my favorite M31 instruments.
Not that larger telescopes don’t have their place with M31 when you want to zoom in on details—and there are plenty of details to be seen here. Everything from a tiny, star-like nucleus, to a massive star cloud with its own NGC number, NGC 206, to a huge system of globular clusters, the brightest of which are visible in an 8-inch scope as slightly fuzzy “stars.”
M32 is the brightest of M31’s satellite galaxies. It is analogous to our own Large Magellanic Cloud, and is impossible to miss 24’13” south of M31’s center. It’s bright and it’s slightly oval, but beyond that, details are hard to come by. It’s an elliptical galaxy, so technically there really shouldn’t be much detail to see here. On the best nights at high magnifications with apertures of 10 – 12-inches, I occasionally think I do seem to be able to make out some sort of very subdued dark features in its halo. This is, however, more than likely averted imagination.
From the suburban backyard, beautiful and graceful M33, The Triangulum Galaxy, can be tough, with only a small round central condensation being visible. That’s not surprising since the galaxy, while relatively bright, extends a whopping 61.7’ x 31.3’. I can almost always find it even from yucky skies, however, if I am careful in positioning the scope 4 degrees 15.0’ northwest of Alpha Triangulii, the apex of the triangle.
From darker skies, M33 is an entirely different story. Not only does a 10 – 12-inch easily pick out its loose spiral structure, several HII regions, most notably NGC 604, a huge analog of our own Orion Nebula, become visible. This is one time you might want to use a UHC filter on a galaxy. It will dim M33, but make its nebulae pop right out. Further enhancing the view (without the filter) are numerous dim stars sprinkled across the galaxy’s face.
Ho-hum, it’s a ho-hummer. I’ve never been a big fan of M34. It’s just too large at 34.0’ to be very striking in an 8 or 10-inch telescope. It’s also set in a rich field and the cluster stars don’t jump out at you as much as you’d think they would even in a wide field instrument. And yet, I must admit that with a 35mm Panoptic eyepiece in Zelda, M34 can be striking, showing maybe 40 bright stars, many of them arranged in curving arcs. “Striking,” yeah, but not “blows you away.”
We’ll end on a high note. Gemini's M35 is one of my superstar open clusters. Not necessarily because it is the most beautiful of the Messier galactics—it’s very rich but a little large at 25.0’ across when compared to nearby M37. It’s that there’s a bonus object here, little NGC 2158, a much dimmer and more distant magnitude 12.2, 5.1’ group located less than half a degree from M35’s center. With a wide field, you get this tremendous sense of depth while viewing the two. A 10 – 12-inch is able to resolve many faint stars in NGC 2158 at higher power. I could even see a few from Chaos Manor South with Old Betsy.
Next time? Next time Messier wise will be in part the marvelous Auriga Trio, M36, M37, and M38. Before I do that, though, I am still planning on bringing you the latest installment in my (some would say scandalous) ongoing love affair with refracting telescopes.