Sunday, August 30, 2015
“The Friendly Stars”
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 shortly 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 today 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 I see from my 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 with me 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 naturally take a telescope
with me (unlike when I fly to remote star parties for speaking engagements). Which telescope? Whether I go visual or video, I’ve decided that will be
my C11 and CGEM 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 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. Was I done with the C11?
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 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 when it was owned by Tasco (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 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. And even when you're doing only a target or two a night with a wide field telescope, sometimes (but not all the time) pointing can be pretty punk. There are fixes for that involving computer software like EQMOD and plate solving applications, but many's the time I don't want to drag a PC into the field.
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 Buddies 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 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 stepper 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. But after that terrible spring and summer weather had closed me down till now.
Confession time. But for the fact 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 indistinguishable from those of a 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 ain't 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 is a very pleasant one--once you have it set up.
“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.
 |
| M10 |
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
counterclockwise 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 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.
 |
| M12 |
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 and nudging the scope around to arrive at the subdued stars of Ophiuchus 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.
This night? No, my eyes are not as good as they were back
then, but 5 additional inches of aperture makes up for a lot of 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 number 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.
 |
| M62 |
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 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 the stars 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 detect a very subdued
blue-gray, but that was almost impossible. 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."
2018 Update
What has changed in the three years since this one was posted? There has been a sea change in my practice of amateur astronomy thanks to the back injury I sustained not long before this was written. I thought it had all healed up, but in the months following this entry waves of back pain let me know I was wrong. Thanks to that, big telescopes and big mounts are no longer an option for me. I tried to keep on with the C11 and CGEM, but it was a no-go. Bertha, CGEM, and Atlas were all sold.
That really wasn't a bad thing, though. I never did much long-exposure imaging with the C11--and long exposure DSLR imaging is my focus in astrophotography now. As I noted above, for simple visual observing from the backyard, it's not much fun setting up a C11 and a big German mount. When I go deep sky cruising in these latter days, it is with my 10-inch f/5 GSO Dobsonian Zelda, who is in some ways actually preferable to the C11. When I want to take pictures, it is with with an Edge C8 or 5-inch APO on a Celestron AVX or Losmandy GM811, both of which mounts are far more pleasant to use than the CGEM or Atlas.
Anyhow, as I tried to communicate in the post above, it's not really the equipment you put into amateur astronomy that makes the difference. It is the heart. Many things have changed in my outlook on life over the last three years, but one hasn't. That long-ago August run with an humble 6-inch Sonotube reflector is still one of the most memorable astronomy nights of my life.
Comments:
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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!
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