Sunday, August 30, 2015
“The Friendly Stars”
The quiet summer night when my City Lights observing runs began, a night over a decade before my essays finally morphed into The Urban Astronomer’s Guide, sometimes seems like it was just yesterday. Not that I miss the early 1990s much; that was a rather lonely time for me. Thank God for astronomy. As I said in the Urban Astronomer's chapter “The Friendly Stars,” when I was under the night sky with my telescope, I had no lack of friends.
I’ve been thinking for a while that it would be fun to revisit the City Lights/Urban Astronomer objects and see how they look to me today. There are admittedly a few more miles on the old eyeballs, which now deliver more than a trace of astigmatism, but I have much more observing experience, considerably more even than when I rewrote the City Lights essays into a book after the turn of the century. Certainly, my telescopes are better than the humble homemade 6-inch Dobsonian I used on that 1993 summer's night. And my skies are considerably better than they were downtown where I did much of the book's observing. Not worlds better, though, but that is the point of City Lights astronomy. “What can you see from your backyard?”
In addition to wanting to revisit my urban objects, I had another agenda. I am looking forward to a busy star party season this fall attending several, at least, regional events. I plan to drive to every one of ‘em—Deep South, Peach State, Maybe Chiefland, too—and I will most assuredly take a telescope with me. Which telescope? Whether I go visual or video, I’ve decided that will be my C11 and GEM mount. That being the case, I needed to check the rig out, since the last time I’d used it had been, almost unbelievably, last February during a somewhat abortive Chiefland expedition.
What happened to my old friend Bertha, the NexStar 11 GPS? I got tired of her late last year. I’d used and loved the telescope for over a decade, so I was more surprised than anybody when I suddenly became dissatisfied with her. Perhaps, in retrospect, that was my first hint that I’d be going through lots of changes in the coming months (I still am). All I knew at the time, though, was that I was sick of lifting my 11-inch fork-mount SCT in and out of my vehicle, and I was weary of egg shaped stars in my unguided Mallincam images. I was done with Bertha.
Or was I? The Celestron C11 has always been the queen of SCTs for me. More practical than a C14, but with a big aperture advantage over a C8. And there has also always been a certain something else about the C11, a certain je ne sais quoi that has nothing to do with the telescope’s optics. In addition, I was loath to sell a C11 with a carbon fiber tube. It’s beautiful and it reduces temperature induced focus shift and they don’t make them like that anymore. Finally, my C11 was one of the last made by Celestron as an American company (Tasco, contrary to popular belief, was an American company), and somehow that further endeared Bertha to me. OK, OK, I’d keep her, but I’d have to fix her.
How the heck would I do that? Simple: G-E-M. I’d put Bertha on a German equatorial mount, which would, I hoped, kill two of those metaphorical birds with one stone. Dispensing with the heavy fork would make the telescope easier to transport, and being on an equatorial mount would improve my tracking. Yes, I had a wedge and could have run Bertha in EQ mode, but the difficulty of mounting that big scope on a wedge made it something I never did. It was a two person operation, and even with a helper was not something I cared to do often. Or at all.
Which GEM? That might have been my Atlas. The draw there was that I had the mount already and wouldn’t have to spend for a new one. The down-check was that while I have gotten a lot of use out of the Atlas for prime focus imaging, I’ve never been happy with its computer. The goto accuracy is fine for imaging three or four relatively bright targets in an evening, but not for imaging 100 a night with the Mallincam.
I’d also have had to change out the mount’s saddle for something sturdier; I’d have had to convert from Vixen dovetail compatibility to the wider Losmandy D system to provide as much steadiness as possible for the C11. That would mean all the other scopes (four of ‘em) I use on the Atlas would have to go “D” as well. The more I thought about it, the less the Atlas sounded like the answer.
My next candidate was a Losmandy G11 Gemini II mount. The G11 is a beautiful piece of kit, several steps above the Chinese imports. It would be expensive at over three thousand dollars, but if it meant I’d be able to continue using Bertha, I was willing to bite the bullet. Or I was till I set up next to a new Gemini II G11 at the 2014 Deep South Regional Star Gaze. The mount was beautiful and finely made, but it was obvious to me that the Gemini II goto system, which Losmandy gets from a third party, was still a work in progress. Didn’t seem too user friendly, and the dude who owned it had a lot of trouble getting it going at all.
I had little doubt Losmandy would soon get the bugs out, but the more I thought about it, the less I was convinced I needed to spend even the relatively small amount of money a G11 commands for my modest requirements.
I thunk and I thunk and I thunk and I came up with two potential candidates, the first being the new Synta (SkyWatcher, Orion) AZ EQ-6. It is the modernized Atlas EQ-6 and is somewhat lighter and prettier than the original and features an alt-azimuth mode and a dual format Vixen/Losmandy D saddle. Nice looking mount, but I eliminated it for two reasons. First, I doubted I’d use the alt-az mode much, since I was sick of that for video with the NexStar 11 GPS. Also, I’d heard from owners that the mount’s goto accuracy with the hand control was more like that of the Atlas than it was different.
Which left me with one mount choice. One that in retrospect seemed perfect. I was amazed, frankly, I hadn’t thought of it first, the Celestron CGEM. The CGEM had a somewhat bumpy introduction, true, but Celestron has worked hard to apply both software and firmware fixes to get the mount up to snuff, I believed they’d accomplished that, and I believed the mount would be perfect for my uses. I didn’t depend on hearsay or what the good old boys wrote about the mount on Cloudy Nights, either; a buddy of mine owned a CGEM and I observed it and observed with it.
What is the mount like? The CGEM, which is another update, Celestron’s update, of the venerable EQ-6, is in much like the older Synta mount. However, it is different in a very important way. In addition to various design tweaks to make the CGEM more modern-looking and ergonomic, the SynScan controller and motors have been replaced by Celestron’s NexStar HC and servos. That NexStar HC ensures the CGEM’s goto accuracy is outstanding. Easily as good as/better than my NexStar GPS, which never missed a target that I can recall. Finally, like the modern EQ-6es, the CGEM features a Losmandy D type saddle.
You can read all about the coming of the CGEM and my deforking of Bertha here, but to make that proverbial long story short, I ordered a mount from Bob Black at Skies Unlimited, and ordered a D type dovetail for the C11 from B&H Photo. Everything arrived when it was supposed to, went together in an afternoon, and came with no surprises. I used the mount two or three times in the backyard, and that one time in Chiefland, and the spring and summer weather closed me down till now.
Confession time. But for the fact that I wanted to give Bertha a clean bill of health for the coming star party season, I’d likely have used Zelda, my 10-inch Chinese dobbie, for the night’s observing instead. If you are going visual, frankly there is no reason to lug out a big, honking C11 and CGEM. The images Zelda, provides are basically indistinguishable from those of the C11. Sure, tracking is nice, but as you-all know, I am addicted to 100-degree AFOV eyepieces, so I am not nudging the scope along all the time. Goto is also nice, but in the backyard I am not chasing minute PGC galaxies and I do just fine with a finder and a star chart. Still, there is no denying the C11/CGEM experience was a very pleasant one.
“The Friendly Stars”
Back when I did the observing for what would become the Friendly Stars chapter in Urban Astronomer, I didn’t have a C11. I didn’t even have a C8 at the time. I was observing with a freaking 6-inch Sonotube Dobsonian I cobbled together in my garage. So, I expected great things of the night’s objects in my big CAT despite the presence of a just-past-First Quarter Moon. The seeing was not great thanks to a front passage, but it was an uncommonly comfortable night. The temperature was plunging, on its way to a record low for us for August, mid-sixties. Certainly nicer than the sticky night recounted in my book.
As above, this night wouldn’t just be about observing; it would be about tuning up the telescope. I’d already accomplished my first task, adjusting Bertha’s focuser. One of the screws on the focuser backplate had loosened over the years, making focus action stiffer than I liked. Ten minutes of tweaking indoors and it was good to go again. What else other than mount checkout? I couldn’t remember the last time I’d collimated the scope, so I thought I should at least check it.
Goto aligned and polar aligned (via the AllStar routine in the hand control), I sent the scope to a bright, but not too bright, star, centered it precisely, and threw it slightly out of focus with a counter-clockwise twitch of the focus control. Just enough to show me the star’s diffraction rings. Yep. Squished on one side.
The rings were, in other words, not concentric. I needed to collimate by adjusting the secondary mirror. I fetched a Phillips head screwdriver from the shop and started twitching screws by small amounts. There are ways to figure out which screw you need to turn given the look of the diffraction rings, but I’ve done this so much that I am comfortable just picking one, turning it (tightening), and seeing if it is the one that needs to be adjusted.
In the end, I loosened one screw by a small amount and that was enough. Yes, I preach that it’s bad to collimate by loosening screws, but if a screw is as snug as it goes, it is OK to loosen its opposite number(s) to keep moving in the proper direction. In fact, you have to. Anyhow, I re-centered the star and gave it a critical check with a 5mm eyepiece. Looked like a little bullseye when the seeing cooperated. I was done.
Next? Over to M13. It wasn’t officially a member of the night’s list, but I went to it anyway for two reasons. First, again, one half of my agenda was checking scope/mount, and I wanted to be sure the gotos were up to snuff. The cluster was nearly at zenith, and the area straight overhead is often a problem for mount goto systems. Not for the CGEM. M13 was almost perfectly centered in a 15mm ocular. Later in the evening I did some further goto testing. At f/6.3 with the reducer corrector screwed onto the rear cell, the CGEM got anything I requested into the field of a 5mm eyepiece at 353X. Yes, it was a 100-degree AFOV ocular, but that is still darned good in my book.
The other reason I punched up M13? As I say in the book, how can you fail to visit Herc anytime he is over the horizon? The cluster, despite the Moon and despite my usual ration of light pollution, was a wonder, a sprawling thing, almost a spider shape composed of tiny stars. It looked best, I thought, in a 10mm eyepiece, which yielded just shy of 180x, which was enough to darken the background sky considerably. I spent a long time staring at the Great Globular, but not too long. As I also observe in The Urban Astronomer’s Guide, dessert only does not a nutritious meal make.
Time to prowl the reaches of the serpent bearer, Ophiuchus, just as I did on that decades ago night. Where to start? With his best of the best, M10, one of the so called Twin Globs. Unlike that 1993 night, when I had to do considerable squinting to make out the subdued stars of Ohiuchus in the summer haze, I just mashed “M-0-1-0” into the hand control, Bertha’s CGEM made its noises (which are at least a little less grating than the CG5’s weasels-with-tuberculosis sounds), and we were there.
What did I say about it back in the day with my little 6-incher (probably equipped with a 25mm Kellner)? I thought M10 was beautiful. When I switched to my prized 6mm Orthoscopic, I could make out plenty of stars around the cluster’s periphery. Heck, I even thought I spied a few near the core with averted vision.
Today? No, my eyes are not as good as they were back then, but 5 additional inches of aperture makes up for a lot of optical deficiencies. In the 10mm 100-degree ocular, M10 was far more beautiful than it had been in the 6-inch. There were still the stars around the cluster’s edges, just many more of them, and looking at the glob’s center revealed still more. And more and more. With direct vision. M10 is a Shapley – Sawyer Class VII globular. It’s loose enough to allow you to easily resolve stars across its face, but tight enough so that it really “looks like a glob.” Wonderful. Get out and look at it tonight, folks.
M12 is the other twin. But it is only a twin in the sense that it’s nearby, about three and a quarter degrees from M10. It looks nothing at all like the previous object. M12 is much looser, a class IX. It’s not so loose than it fades away into the background like the really loose NGC 5053, but it was loose enough to be somewhat of a pain in the six: “I was disappointed...it’s not nearly as good from this suburban site as I’d hoped. It is a vague, ghostly glow 3’or 4’ in size at most in my scope.” I did note a little central condensation, signs of the cluster’s core, but that was not easy. Worse, I couldn’t resolve a single star anywhere in the cluster, even with a magnification of 250x.
Again, the 11-inch made plenty of difference. It still wasn’t like looking at a photo taken from a dark site, but it was very obviously a globular star cluster showing a goodly numbers of stars both at its edges and, thanks to its looseness, in the core area. In the C11 the central region was easily distinguishable with direct vision. It wasn’t as good as M10 by a long shot, but still good.
Onward. Next up was Messier 5, which on an above average night can impress me more than M13. This was the only object of the evening where the 6-inch came close to equaling the C11. And that was only because Serpens’ big-glob was in the trees and being partially blocked. Frankly, the view was still better in the C11, where I could make out stars near the core, but nevertheless the impression was much the same as it was with my old cardboard dobbie: “Lovely with a compact core. 200x reveals plenty of outlying stars but not many in the center.” The cluster is strongly elongated, something I picked up on easily with my small scope and which was obvious in Bertha.
The next Friendly Stars DSO, M107, wasn’t just skirting treetops, it was completely blocked, so I bypassed it and continued on to another Ophiuchus globular star cluster, M62, which was in an open area. This is a rather tight Class IV glob, which makes it nice and bright and easy to pick out even for observers at more northern latitudes. While M62 is bright looking and actually bright in fact at magnitude 6.5 and 15’ across, it’s dimmer and smaller than the previous globs, and I had to use high magnification, averted vision, and a dark cloth over my head to keep out stray light in order to resolve a few stars with the sixer.
Once again and not surprisingly, the C11 made a difference, if not a huge one. Yes, a dozen or so stars were visible with direct vision, but they were not overly easy, and the impression was mostly “grainy-looking” rather than “resolved.”
If you’re going to tour Ophiuchus, you have to be in the mood for globular star clusters, since they are his most prominent objects. They are not his only objects, however. There is also a pretty little fuzzy of a planetary nebula, NGC 6572, a.k.a. “The Blue Racquetball Nebula.” It lurks not far from 67 and 70 Ophiuchi and is not hard to track down even without goto.
The problem comes when you get there. Can you distinguish the Racquetball from a field star? The object is bright at 9th magnitude, but also small at 11” across. In the 6-inch I had a hard time telling it from a star even with the 6mm Ortho. In fact, what keyed me in that I had found it was the object’s striking blue color, which made it stand out immediately.
|The Blue Racquetball...|
In the C11, it was easier to pump up the power to over 300x and resolve the planetary as a little fuzzy racquetball (I think tennis ball is actually more apt). The funny thing, though? Barely a trace of the planetary’s blue color did I see. I thought maybe, barely, I could describe it as a very subdued blue-gray, but that was almost an exaggeration. What was the problem? Worse seeing than that 1990s night? Too much glass in my 9-element eyepiece? Older eyes? Who knows? I’ll have to come back to this one before the season is out. I long to see that face-slapping color again.
And that was it. Oh, I didn’t intend for that to be it. There were a few more objects in my list, and I wanted to backtrack to M107 when it was out of the tree leaves, but that was not to be. As sometimes happens, the leading edge of the front had some clouds behind it and they closed me down for all practical purposes. The Moon was higher now, too, definitely interfering badly. I threw the big switch.
One especially important thing I remember from the end of that long ago Friendly Stars night? That when I finished observing I felt a lot less lonely than I was when I began:
"Lonely? By the end of the night I didn’t feel a bit lonely. After soaking in so much beauty, the night and the Universe didn’t seem mysterious or forbidding. Even the distant, enigmatic globular clusters seemed no stranger than friendly bees buzzing around the hive of the Milky Way’s center."
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Hi Rod! The story of "Bertha" struck very close to home. This was my first serious instrument (after ohhh so iffy 8" B&L SCT). I bought mine on 04/18/2004 at NEAF from Skies Unlimited. Incredible for $2999! She serves me to this day in the original configuration (with 3rd generation of HC) well. I use her these days mostly in Hyperstar setup to do Deep-Sky photography. Always on target, great optics. I never refurbished it, which I probably should, at least to realluminize main mirror. Just cleaned corrector plate once a year. It is amazing how much I can image across the Hudson from the NJ side in the white zone, albeit through narrowband filters. Tracking is up to snuff too. I've been routinely doing 10 min subs, guided, round stars. In any case, good luck with your new mount. I will use my fork, though. It is heavy, but I was able to always put it together myself. So, until it gives up on me NS11 rules!Post a Comment
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