Sunday, June 22, 2014
Good Old CG5 (and a Little RSpecing)
Plenty of y’all liked
the Celestron CG5, muchachos; even members of the “An A-P Mach 1 is the minimum
mount for astrophotography” crowd admit it was a pretty good little GEM (German
Equatorial Mount) for very little money. But it still doesn't get all the credit
it deserves. Mainly for being the mount that gave plenty of near-cast-off 1980s
and 1990s SCTs a second lease on life.
Howsomeever, I come here not just to praise the CG5. No matter how fondly we remember
Celestron’s first popularly priced go-to GEM—it was superseded last year by the
new VX—it was not perfect. Not hardly. And reviewing some of those
imperfections may help elucidate the situation regarding the VX,
which—surprise—ain’t perfect either.
The GEM we know and love as the CG5 wasn’t actually
Celestron’s first CG5. By the mid 1990s, the company was selling Chinese clone
copies of the Vixen mount formerly sold with the Great Polaris C8, which was the follow-on
from the company’s earlier C8 + GEM configuration, the Super Polaris C8. The GP C8 was popular, but it was only popular at
a price point around 1000 dineros. With Vixen gaining popularity at the time and
increasing prices out of all reason, that price point was impossible for
Celestron to maintain.
Enter the CG5. The initial CG5 looked a lot like what we
think of as a CG5 today sans motor housings and an electronic control panel. No
go-to for this 90s GEM. You could, however, order it with a pair of bolt on
Chinese motors that provided tracking and slow motion/guiding via a dual axis
HC that ran off D batteries. Superficially, it looked a lot like a Great
Polaris down to the D battery bag with its silly little “purse” handle.
Appearances often deceive in the import scope biz, however,
and the CG5 was no exception. It was OK, mind you, especially if you took the
time to clean out the Chinese glue-grease (made of ground up weasels,
apparently) and relube it. Unfortunately, though, it didn’t have ball bearings.
Plastic sleeve “bearings” were on both axes and that limited the mount’s
performance potential. My long-time observing companion Pat Rochford had one of these proto CG5s
for a while, which he rigged up with the Mel Bartels home-brew go-to system,
and while his mount worked, it just barely
worked.
When Celestron announced a go-to configurated CG5, the
“ASGT” CG5 (Advanced Series Go To), I was appalled. Given my experiences with
Pat’s CG5, I couldn’t believe this would work reliably, not unless major
improvements were made to the mount.
Celestron (and Synta, the mount’s Chinese maker, who was
soon to own Celestron) knew that, too, and had made improvements. The glue
grease was gone. While the bearing situation on the declination axis was
unchanged, there were now ball bearings on RA. The mount was also somewhat (if
not a whole lot) better finished. The bolt-on motors had been replaced by
servos in plastic housings. The non-goto CG5’s dreadful extruded aluminum
tripod was trashed in favor of a hefty 2-inch diameter tubular steel-legged
job. Maybe most importantly, go-to was furnished with a standard Celestron
NexStar HC, which was getting better all the time.
Unk was still skeptical but not immune to the ASGT’s charms.
I had been spoiled by the goto on my NexStar 11 GPS, which I got in 2002, and
it was getting ever harder to make myself use my old fork mount Ultima C8,
Celeste. Which was a shame. She had good optics, especially by the standards of
the mid 1990s. Didn't matter. I was over
polar-aligned fork mounts. I had had enough of navigating the sky with
finder, Telrad, analog setting circles, and freaking Sky Atlas 2000.
Anyhow, it sure would have been nice to have a go-to rig a
little lighter than the NS11. There was the non-GPS NexStar 8, but that
telescope and the similar NexStar 5s I’d tried left me cold regarding their
so-so go-to accuracy. Howzabout a NexStar 8 GPS? Unk, stingy then as now,
didn’t want to pony up that much cash.
Hokay, I’d get me a cotton-picking ASGT CG5. Just the mount. I’d defork the Ultima 8 OTA,
and give it a whirl. If I decided I liked using a C8 on a goto GEM, I’d put the
CG5 on Astromart and get a good goto
GEM. A Vixen or a Losmandy or sumpin’. I was sure the CG5 wouldn’t have the go-to chops to keep me happy.
My purchase of a CG5 was not without incident—Unk’s
astro-gear purchases never are. On its way to me from Anacortes, Washington in
the spring of ought five, the UPS truck it was in crashed and burned on the Interstate--or so I was told, anyhow. Anacortes Telescope and
Wild Bird got another one on its way to me promptly, however, and the delay
gave me time to figger out how to get the C8 off her fork and equipped with a dovetail. It turned out that wasn’t much of
a task. Removed some screws, and the Ultima 8, Celeste, was free of her
old-timey mount. A few dollars to Scopestuff
for a dovetail and maybe 15-minutes attaching it to the tube and we was ready
to go.
As I have told y’all before, I was gobsmacked when I got the
C8/CG5 combo into the backyard. I hadn’t expected much in the way of goto accuracy;
nevertheless, after a simple three-star alignment, the mount placed anything I
requested smack in the field of my 12mm Nagler. The hand control operation was
identical to that of the 11 GPS, and Unk just fracking zoomed around the sky. The first night, anyway.
The second night? That
was testimony to the split personality of the CG5. After my success at first
light, I was anxious to give the mount a second night in Chaos Manor South’s
backyard (which in the early spring of 2005 still had enough openings among the
trees to allow me to see a few things). Started the alignment, the scope headed
for star one, and kept right on going past it till I killed the power. “Well,
hot damn. Dadgum thing lasted all of one night!”
The declination axis seemed to be the problem, so I opened
up the motor housing. All seemed well. I put it back together and hit Chaos
Manor South’s kitchen computer for a look through the archives of the (already
burgeoning) ASGT Yahoogroup, which I’d joined when I first ordered the CG5. I
was swiftly edumacated about one of
the mount’s Achilles’ heels, POWER.
Seemed as this was one power hungry sucka. I was accustomed
to getting two nights (partial nights, anyway) out of the NS11’s battery
without charging it. That, I read, was not going to be the case with the CG5.
If you didn’t start each evening with a fully charged batt’ry you was in for t-r-o-u-b-l-e.
There was also the mount-side power connector. The center pin of which was
composed of two halves that apparently never made good contact with the power
cord’s connector.
The simple solutions, I read, were to charge your battery,
natch, and use a knife or jeweler’s screwdriver to gently spread the pin
halves a mite. I did both things and hoped for the best on night three. I was
rewarded with sterling, nearly unbelievably good, performance. It is no
exaggeration to say I saw more with the C8 in the first year it was on the CG5
than I had with it the previous ten years. Celeste went from being a bench
warmer to being my most used scope again.
So the goto was good. How about tracking? Not bad, not bad
at all. Now that I had a manageable C8 on a go-to mount, I decided it was time
to try that electronic imaging bidness again via the inexpensive Meade
DSI. When I used the NexStar HC’s built in polar alignment procedure (the old
pre-AllStar one that had you center Polaris), I could easily get decent
unguided 30-second sub frames I was able to stack into nice finished shots.
When I moved up to a big-boy cam, an SBIG ST2000, I could do 10-minute self
guided shots without much hassle.
 |
| DSI Dumbbell |
As always, when it came to the CG5’s nature there was a good
angel and a bad angel, however. Yes, the scope could guide well (some users had
problems with stiction in dec guiding, but I never did). BUT… only if you were properly balanced, a
little east heavy that is. Ignore that and you would get trailed stars. Move to
a different position in the sky, maybe closer to the horizon, where your
balance was not so hot? You’d get star trails again if you didn't re-balance. A
pain in the butt, yeah, but manageable considering the mount’s 800 buck price
tag.
I loved doing visual observing with the help of the CG5’s
wonderful goto system, but that wasn’t perfect either. Those of y’all used to
Celestron’s current GEM mounts, the VX, the CGEM, etc., are more than familiar
with the 2+4 alignment method. Align on two stars, add (up to) four calibration
stars, and your gotos are crazy good all over the sky. But did you know
‘twarn’t always so? That the original CG5 didn’t have no calibration stars?
What it had was a three-star alignment like the current
SynScan mounts. That was OK, but, as with the SynScans, you had to be damned
careful about your alignment star choices. As I found out during the mount’s first
visit to the Chiefland Astronomy Village. That was, I recall, in the spring of
2006, and on the first night, things didn’t go as I’d hoped. As usual, I just
accepted the three stars the alignment routine offered. Now for some Virgo
galaxies! Alas, anything I slewed to was on the hairy edge of a low power
eyepiece or just outside the field.
Standing on the crowded observing field looking up at the rising Realm of the Nebulae (Galaxies) with Pat Rochford, I
thunk and I thunk. “Hmmm…the first two alignment stars shore were low on the
horizon.” I powered down, did another three-star, and rejected the first stars
the HC offered, selecting a pair a little higher up. BAM! Anything in the Virgo cluster was well within the field of my
12mm Nagler eyepiece again.
These were early days for the CG5, and Celestron was
continuing to work on its HC code, so I figgered there would be improvements. I
also knew those improvements would come at a cost. The original CG5 HC, you
see, just like the original NS11 HC, was not upgradeable. Want improved
firmware? That meant a new HC at worst or sending the controller back to
California at best. Luckily, by the time I got my mount, Celestron had fixed
the worst faux pas in the CG5 code—which
caused runaway slewing during gotos and guiding.
 |
| A cold CAV January, 2009... |
As I’d hoped, Celestron soon came out with a user-programmable
hand control, and the improvements in the CG5 firmware began to come thick and
fast. Some were a godsend, like the 2+4 alignment routine, others, like AllStar, took a while to catch on with me. While I usually
ran the mount with NexRemote, I nevertheless
bought a new “Version 4” programmable hand control for those times when I didn’t
want to tote a computer. The 2+4 alignment was so good that after that firmware
upgrade (version 4.10), I never used the original hand control again.
Finally, about five years in, another notorious CG5 problem
bit Unk. The mount’s control panel was small and the power switch was
correspondingly tiny. It was also crappily made. I have never heard of a CG5
switch that’s lasted more than five years.
Luckily, I knew what to do when the switch failed on me.
Power light wouldn’t come on. HC was dead. I unplugged from the battery and
exercised the switch mucho times. Plugged the power cord back in, turned the
switch on and the power came up. I knew
it wouldn’t last, though. Once that little switch went, it was a gone pecan.
The answer—if you were lazy like Unk and didn’t want to replace the switch—was to
leave it in the on position and turn power on and off by plugging and
unplugging the cord. Not elegant, but it worked and still does.
Yeah, the CG5 was a great mount but it wasn’t perfect now
matter what old timers like Unk “remember.” The new VX is considerably better
in comparison. The CG5’s corners have mostly been rounded off. That nasty
little power switch and iffy connector have been replaced. The finish of the
mount is mucho bettero. It’s even a little quieter than the CG5, which as I
have said more’n once sounds like a weasel with tuberculosis when slewing at
high speed.
None of which makes me or the other folks who’ve received a bum
VX feel much better, of course. As I related here,
my initial mount head had improperly threaded holes for the declination shaft’s
toe-saver and, fatally, for the tripod’s threaded rod. Bolted mount to tripod
and that central bolt locked forever.
The up side, however, is not just that my replacement mount
was perfect, but that us VXers didn't have to live through the travails of the
CG5’s early adopters: runaway slews,
punk alignments, slow boat gotos to nowhere, and more. The VX has had a few
problems, but its introduction has been a helluva lot smoother than that of the
old reliable CG5.
The CG5 did mature, however, at least vis-à-vis the hand
control and its firmware (mechanically the mount never changed much over its
lifetime). In the end, the CG5 became a SOLID performer. But what’s it like to
use one today, in this day of the VX and the innovative mounts coming out of places
like iOptron? Unk thought he would find after not giving the CG5 a real workout
in over a year. I’d had it out a few weeks back for some casual videoing, but I
didn't take much care with the alignment or try to determine how it compares to
the Victor X-ray. I also thought I might kill two chirpers with one rock.
I last reported on RSpec
and the Star Analyser diffraction grating in January. Your old Unk was just on
the crux, he thought, of learning the difficult art of astronomical
spectroscopy using these excellent tools. RSpec
is the software that allows you to acquire and analyze stellar spectra ; the
Star Analyser is the 1.25-inch filter-like diffraction grating you screw onto
your camera to turn stars into rainbows.
I was beginning to make progress, but then some things intervened.
Mostly, the weather. As I don’t have to tell my fellow Southrons, it was a
crazy-cloudy winter and early spring south of the Mason Dixon line. I got out a
few times, but only a few, and the only really successful outing over those long
months was at the 2014 Deep South Regional Star Gaze Spring Scrimmage, where I
was busy wrapping up the reimaging of some Herschel Project objects.
Now that June’s here, the skies have improved, though they
are not perfect—that would be a lot to ask for on the Gulf Coast with summer
coming in—and at the New Manse I can now observe from my backyard. There’s
light pollution, and, worse, it’s been continually hazy, but that didn't hurt
my lunar imaging none, and I didn't expect it would stop me from RSpecing
either.
Setup last Saturday night was a leetle different. As I’ve
mentioned previously, my best view of the sky is near the deck. I plunked the
CG5 tripod down there, positioned a little table on the deck for my laptop, and
put all the pieces together: Celeste on
CG5, flip mirror in rear port, ZWO camera on flip mirror. Hooked the mount to
the laptop via the NexRemote cable
and got ready to rumble.
Need it be said that Uncle Rod’s observing runs do not
usually go smoothly? My problems on this evening had nothing to do with the
CG5, howsomeever. I had to pick a few alternate alignment and calibration stars
due to trees, but that was it. Last cal star was near the center of my old
Meade 12mm reticle eyepiece when the slew stopped. Polar alignment (via
Polaris; stars to the south that would be good for AllStar are currently
blocked by a tree) was a breeze. My last calibration star was Vega, so I left
the mount sitting there. RSpec’s
author, the talented Tom Field, advises you to begin with Vega when you are just
learning, since it has a very prominent h-beta line, and is easy to
“calibrate.”
I had used RSpec
several times before, so I shouldn't still be “just learning,” but I had a
sneaking suspicion I would be anyway. Too many months without using the program
left me foundering. “How do I get it to connect to the ZWO camera? How do I set
the exposure? Where do the files go?” I fooled around and fooled around, locked
things up a time or two, restarted a few times and finally got back in the
swing of things. Did a couple of .avi sequences of Vega, and moved on to
Arcturus, Spica, and Aldebaran.
What’s it like using the CG5 in lieu of the VX? It ain’t that much different, y’all. Certainly
the CG5’s goto is every bit as good. It was routinely placing stars on the tiny
chip of the ZWO planet cam at f-freaking-10. Otherwise, about all I noted was
that the mount does have more declination backlash than the VX. Reverse
declination directions, and it can take quite a while for the mount to start
moving. Not at all unmanageable, but worse than in the newer mount. Oh, and
it’s definitely louder than the Victor X-ray. My new next-door neighbor stuck
his head out mid-evening, no doubt wondering what that weird whining noise was.
 |
| Vega... |
Last star in the can, I retired to the den to watch the remainder
of Svengoolie, who was showing a good one—Evil
of Frankenstein—after a long dry spell. A little Yell and a little Hammer horror and
it was soon well after midnight and time for some shut-eye. As always, I didn't
even peek at my images; that would wait for morning.
Sunday morning, I did yet more fumbling on the way to getting
my spectra calibrated (converting pixels to angstroms, that is), but I got ‘er
done despite the fact that during our move I lost the RSpec cheat-sheet I’d made up. I still have a long way to go with spectroscopy
and I am starting all over, but Vega,
from what silly old Unk can tell, is my best spectrogram yet. RSpec was great. The Star Analyser was
great. The ZWO was great. But what was the greatest despite its few blemishes was my wonderful old CG5. Long may she wave, muchachos, long may she wave.
Next Time:
Revenge of the Return of the Denkmeier…
Comments:
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nice article Rod, I still use my old Super polaris mount. its not goto but the setting circles work well with a level mount [imagine that ], the polar scope gives decent alighnment adjusting for the present date and the tracking unguided is good for first 4-5 minutes.... no computer, no xs cables , just plain old analog technology at its best. regards Howard
# posted by 
: 2:10 PM
: 2:10 PM
Thanks to your books and blogs, I bought a CG5 for an early 2080, added a set of wheels, and am very pleased. Thanks for your expertise and writing style.pp
I really enjoyed the information on how the CG mounts evolved. Sometimes "deals" come up on the resale market. This information is helpful in evaluating these mounts.
Tom Wall
Tom Wall
I bought a CG5-ASGT last October. I never knew about your blogs until this past spring. I went on the assumption that is was a good goto mount based on some CN reviews. I like my CG5. I always do 2+4 stars for aligning and calibration. Most of my slews bring the object into the field of a low power ep. I know the sky very well and if the object is out of the fov, I can usually find it without too much trouble.
I like your blogs, just wish they were more frequent.
Deepskydave
Waltham, MA
I like your blogs, just wish they were more frequent.
Deepskydave
Waltham, MA
# posted by : 11:40 PM
: 11:40 PM
Great entry as usual. Question for you...your go to dealer (and my local shop) has a used CG5 ASGT for 349 clams. Should I jump on it or save my dollars for th AVX?
I'm going up tomorrow and talk to señor black. It looked pretty good but I didn't play with it. Bob might let me take it home and try it out
Hi - I am looking at a used $500.00 Advanced CG5 vs a Celestron VX at $719.00
Any suggestions?
Any suggestions?
# posted by : 11:41 AM
: 11:41 AM
There is not much difference between the ASGT and the AVX, I have owned both.
The AVX has a USB port instead of serial port, is just slightly quieter, and has some extra aux ports which probably won't get used. The fit and finish is a lot nicer than the ASGT and the plastic covers feel a lot more solid. For $350 the ASGT is a great deal. If you can swing the price of the AVX go for it, it IS a bit nicer, but there is not really much difference in performance. I would not feel bad for choosing a $350 ASGT over a $800 AVX.
I definitely would not pay $500 for an ASGT though... $400 max if it's in perfect condition.
The AVX has a USB port instead of serial port, is just slightly quieter, and has some extra aux ports which probably won't get used. The fit and finish is a lot nicer than the ASGT and the plastic covers feel a lot more solid. For $350 the ASGT is a great deal. If you can swing the price of the AVX go for it, it IS a bit nicer, but there is not really much difference in performance. I would not feel bad for choosing a $350 ASGT over a $800 AVX.
I definitely would not pay $500 for an ASGT though... $400 max if it's in perfect condition.
ASGT and AVX are light and reliable.
Here are the differences:
AVX has a nice screw on polar scope cover. The ASGT version always falls off.
AVX has nice large dovetail and latitude adjusters bolts vs small ones on the ASGT
AVX finish is nicer, plastic housings are thicker.
AVX dec motor housing does NOT rotate with the scope like the ASGT.
AVX locking levers are 1/4 turn. I actually liked the ASGT locks better.
AVX is a bit quieter when slewing.
AVX has USB instead of requiring an additional USB->RS232 converter. This is convenient but actually sort a downside because serial cables can be run much longer than USB cables, and you are stuck with the dreaded PL2303 driver instead of being able to use a more mac friendly driver. It does work tho.
More ports on the AVX for additional accessories
AVX power cord is in a dumb location and gets pulled out easily.
AVX has no bubble level and nowhere to stick one. I miss this from the ASGT.
AVX dec port points straight UP... and gravity pulls dew straight down. Guess where the dew goes?
AVX dec bearing/bushing is very sticky. The ASGT is better in this regard, but not sure why since the internals are almost identical.
Hope this helps.
Both mounts are amazing with an 8" SCT. Build an adjustable observing chair and you are all set.
Post a Comment
Here are the differences:
AVX has a nice screw on polar scope cover. The ASGT version always falls off.
AVX has nice large dovetail and latitude adjusters bolts vs small ones on the ASGT
AVX finish is nicer, plastic housings are thicker.
AVX dec motor housing does NOT rotate with the scope like the ASGT.
AVX locking levers are 1/4 turn. I actually liked the ASGT locks better.
AVX is a bit quieter when slewing.
AVX has USB instead of requiring an additional USB->RS232 converter. This is convenient but actually sort a downside because serial cables can be run much longer than USB cables, and you are stuck with the dreaded PL2303 driver instead of being able to use a more mac friendly driver. It does work tho.
More ports on the AVX for additional accessories
AVX power cord is in a dumb location and gets pulled out easily.
AVX has no bubble level and nowhere to stick one. I miss this from the ASGT.
AVX dec port points straight UP... and gravity pulls dew straight down. Guess where the dew goes?
AVX dec bearing/bushing is very sticky. The ASGT is better in this regard, but not sure why since the internals are almost identical.
Hope this helps.
Both mounts are amazing with an 8" SCT. Build an adjustable observing chair and you are all set.
# posted by : 11:36 PM
: 11:36 PM << Home
