Sunday, April 15, 2012


A Gem of a GEM

I am not talking about the AP900 or AP1200 or Mach 1, though it could be argued any of them deserves that appellation, muchachos. I’m not talking about the G11 or the Atlas/EQ6, either, though they have a much bigger user base than the high priced spread and are the bread-and-butter performers for many amateurs. No, I’m talking about the GEM, the go-to German equatorial mount, that is so cheap that (almost) anybody can own one. And it is very, very good, too. Yes, brothers and sisters, I am talking about the ubiquitous but too-seldom praised Celestron CG5.

Last week, I told y’all why I decided to defork my C8, Celeste, from her beautiful Ultima mount. Making up my mind to do that was only half the battle. Once I was resolved, the question became “Which GEM?”

Seven years ago there were plenty of go-to German equatorials to choose among. Starting at the top with APs and Losmandys (“Losmandies”?) and Takahashis. But Unk’s requirements were “light and cheap,” which purty much eliminated all those and their cousins from Mountain Instruments and Bisque and even Vixen. What was left was, big surprise, Meade and Celestron. I eliminated the Meade right quick. They did not at that time sell their GEM without an OTA, and I had not been impressed by the performance of the LXD 55 I’d seen on the field at the Chiefland Astronomy Village, though it would have been perfect price and weight-wise.

The last GEM standing was the Celestron CG5, which to my eyes looked a lot like Meade’s mount. This Synta (Chinese) clone of the Vixen Great Polaris did have a couple of strengths, however; it used the Celestron NexStar hand control, with which I was intimately familiar from using the one on my NexStar 11 GPS, and which I liked a lot. The CG5 also seemed to be getting better press than the sometimes problematical LXD 55 (or its successor, the LXD 75).

My brass-tacks bottom-line opinion? I liked the size and specs of the CG5, but I was not convinced this (relatively) cheap imported thing would work very well or for very long. It would at least allow me to give the GEM concept a try without spending a lot of money. I could see if I liked using a German mount with an SCT. If that was a “yeah,” onto Astromart the CG5 would go, and I would bite the bullet and look into a Vixen GPDX or a Losmandy GM8, maybe.

In the spring of ought five, I was ready to pull the trigger. Back in them days, Anacortes Telescope and Wild Bird was a Celestron dealer, and I often ordered from them despite their far away location near Seattle. I sent AT&WB my credit card number, and sat back and waited.

And waited…and waited. Strange and conflicting data on the FedEx website when I entered my tracking number impelled me to give Anacortes a call via voice. After a little checking, they said the truck carrying my mount had crashed and burned on the Interstate (!). Oh, well, they said they’d get another on its way to me tout suite.

The wait wasn’t all bad. It allowed me to get Celeste’s OTA squared away. I won’t give you details on how I tearfully removed her tube from her huge and beautiful fork—if you are interested have a look at this—I will just say I did the deed. I ordered the Vixen compatible dovetail the CG5 required from, and it arrived in just a day or two—how does Jim do that? Installing it on the C8 tube was maybe half-an-hour’s work.

Eventually, the glorious day arrived, the knock on the door came and soon my new acquisition was sitting in Chaos Manor South’s front parlor. Two big boxes, one for the GEM head, one for the tripod. A few crossways glances at the manual, and I had the thing together. Wasn’t much to it: the mount attached to the tripod head via a threaded rod that was secured on its other end by a knob snugged-up against the accessory tray. One of the two 11-pound pancake weights shipped with the mount went on the counterweight shaft, and that was it.

Took all of two minutes to get Celeste on the CG5; there was a large knob-headed bolt that secured the scope’s dovetail bracket in the mount’s saddle, and a smaller “safety screw” to hold the telescope in place if the big bolt were accidentally undone—which has saved Unk’s bacon a time or two. Shiny new mount and still-beautiful black Ultima OTA before me, I stepped back and admired Celeste’s new garb for a while.

You know, almost in spite of himself, Unk was getting excited about this “bargain” mount. No, the GEM head was not a machined work of art, but it was sturdy enough and reasonably attractive. The tripod? A winner from the get-go. 2-inch diameter steel legs and nary a bit of plastic anywhere. I immediately pronounced it superior to the (cheapened) Heavy Duty Field Tripod that came with the NexStar 11.

The CG5 looked good, but would it work good? Only a trial under the stars would tell. Amazingly, the New Scope Curse seemed to be in abeyance. There were still several hours left before darkness on this spring afternoon, however, and I decided to occupy them by doing a fake alignment indoors to see if the CG5 at least appeared to operate correctly.

I had downloaded the CG5 manual from Celestron’s website some time before, and had been pouring over the tips on the mount’s Yahoogroup day in and day out, so I figgered I at least had a semi-idea as to how an alignment should go. Nevertheless, I browsed through the manual one last time. Hokay. No time like the present. I fetched a jumpstart battery pack and hooked it to the mount with the included DC cable. Plugged the HC into the proper port on the CG5’s control panel. Connected the declination cable to the appropriate sockets on the declination housing and control panel, and it was at least semi-rubber-meets-road time.

Alrighty then. Flipped the big (actually tiny) switch to o-n. Success! At least the HC display lit up and a teeny-tiny red l.e.d. on the panel glowed. Following the instructions displayed on the hand paddle, I entered date, time, time-zone, DST status, and lat/lon as I would with any go-to rig. Almost ready to begin the alignment, but first the CG5 had to know its starting place. You tell it about that by loosening the mount’s locks and setting the R.A. and declination axes so the marks on labels pasted to the mount line up.

The initial CG5 firmware, like that of today, offered several alignment modes including Three Star Align, Solar System Align, and Quick Align. Back then, the most accurate go-to alignment method was Three Star. The mount would pick three stars, slew to those three stars, and you’d center each in the finder and the main scope.

The first thing I noticed during the alignment procedure? This was one loud mutha. Easily as loud as an LX200 Classic. I just hoped that it wasn’t quite as loud as it sounded, or that I’d get used to it. I eventually did, but this is not a quiet mount when slewing at full speed. Not hardly.

After the third star—I didn’t pretend to center anything; just hit the Enter and Align buttons on the hand control each time the mount stopped—the HC pronounced “Align Success.” And it did appear to be successful when I did fake go-tos to several bright stars. The scope definitely pointed close to the positions the stars would be in at the current time of day. ‘Course, “close” only counts in horseshoes and hand grenades, so I’d have to wait for dark to learn the truth of the matter. Nevertheless, I felt reassured.

My cat Jellyorum and sister Bombalurina  (r) admiring the new rig.
It was a long, long afternoon, but it finally came to an end and I set up the CG5 and Celeste in the backyard. Seven years ago, our outback was at least acceptably tree-free in early spring. You might have to look through a few budding branches, but you could still, unlike today, at least see something. Set up done, I was getting antsier and antsier waiting for Polaris to make his appearance so I could polar align.

Ah, yes, polar alignment. Oh, joy. Unlike an alt-az fork mount, a German equatorial must be polar aligned to track well, and some need a good polar alignment for best go-to accuracy. Not the CG5, apparently. Its go-to, I’d been told on the Yahoogroup, wasn’t much affected by polar misalignment. That was later borne out when a fellow club member “polar aligned” his mount on Kochab, and had lousy tracking but excellent go-tos. Anyway, I wanted to give the mount every chance to succeed, so I thought I’d at least roughly polar align it.

How’d I do that? I did not purchase the optional CG5 polar alignment borescope. The one I got with the non-go-to CG5 (EQ4) that came with Old Yeller was almost completely worthless, and I had read that for visual use sighting Polaris through the empty polar bore of the CG5 was good enough. I removed the plastic end-caps from the RA axis, moved the scope in declination 90 degrees to open up a hole in the declination shaft, and adjusted the push-pull azimuth and altitude bolts on the mount till Polaris, flickering just above the roof of The Old Manse, was centered. Returned the mount to its start marks, and got ready to rumble.

OK, Three Star. The mount stopped a fair ways from all three stars, but not an outrageous ways away from any of them. I centered ‘em in the finder, hit Enter, centered each in Celeste’s eyepiece (a 12mm Meade crosshair job), mashed Align, and went on to the nextun. The final star was obscured by a tree in the yard of the house next-door, so I hit the Undo button on the HC till it offered a star that was in the clear. When I was done, the hand control thought for a minute and pronounced “Align Success”. Well, I reckoned we’d see about that. I didn’t have much hope this noisy rig would find pea turkey.

Removed the reticle eyepiece and inserted my beloved 12mm Nagler. What was in the tree free area to the east? Looked like M63 was. Ort to be able to see that bright one despite the sodium streetlight-orange sky. The mount made the noises I’ve since come to describe as sounding like “weasels with tuberculosis,” and eventually came to a stop. Yeah, Celeste was pointing in roughly the correct direction, but, naw, no way. Couldn’t be. The only question I had was “How far off is it?”

Eye to eyepiece, and I nearly dropped the iced tea glass of Rebel Yell that had, not surprisingly, accompanied me into the backyard. Well, I’ll be DAGNABBED (this is a family-friendly blog, y’all). There she was. Not just in the field, but dang near centered. Had to be luck.

Nope. So was M53. So was M87. So were M84 and M86. Maybe I was being too easy on the thing. Those spring DSOs were in the neighborhood of one of the alignment stars. What about the other side of the sky? Looking west, I spied Andromeda plunging into the horizon in a gap between an oak tree and my neighbor’s house. I punched-in “M110.” I had to squint a little to see it, but, yeah, there it was. To say I was elated, gobsmacked even, would be an understatement. Alas, my feelings of joy lasted all of 24-hours.

The Sunflower. taken with Celeste and the CG5
Next evening was clear, too, so naturally I got my wonderful CG5 out back again. Aligned just like I had the night before. Sent her on her first go-to, and… Disaster struck. The mount moved Celeste in the proper direction, but kept on going past the target. Slowly. Sounding not just like a weasel with tuberculosis, but one on its last legs. I killed the power. Started the alignment over, and this time that went to hell, too. The CG5 chugged slowly past the first star on its way to who-knew-where. “Well, that’s about what I expected, gull-dern fracking thing lasted all of one day!”

The problem seemed to be only in the declination axis, and Unk ain’t a-feared of a little tinkering, so, with the mount back inside, I found a screwdriver and opened the declination housing. Nothing was amiss enough to reveal itself to a visual inspection. Hmm. Cleaned the contacts on the dec cable and receptacles, closed everything up, and sat down to ruminate.

Thinking about what I had read about known problems with the CG5, two things seemed to be most common: poor power and a poor connection to the mount’s power receptacle. Power? I had done a lot of go-tos the previous night and hadn’t recharged the jump-starter, but the battery wasn’t completely dead, and my NS11 would run fine for two similar sessions on the same battery. Nevertheless, I put the jump-starter on charge.

I knew lots of folks had had trouble with the power connector on the mount. Luckily, I’d heard the fix was simple. The center pin of the mount-side jack is in two halves; all you had to do was spread ‘em apart a little to ensure a firmer connection. Which I accomplished with a jeweler’s screwdriver. What now? Have to wait till the next night, when the battery was fully charged again.

Next evening, you can bet old Unk hauled the mount out back with a purty good ration of trepidation. Started the alignment. At least that went OK—but it had the first time the previous night, too. First go-to… Bang on. Second go-to? Same-same. And so it went for the rest of the run. What caused the problem, the battery or the connection? In retrospect, probably both. Over the years I’ve learned that if you want good performance from the mount, you always start with a fully charged battery. The power connection is just as critical. Spreading the pin that one time was enough to do the trick, and I have never had to revisit it.

One other thing I did? I ordered a new 12-volt power cable. The one Celestron included then and now was made of overly thin wire and it was long. At least twenty feet. That is no good at all. The voltage drop that results can’t possibly help the mount. Why is it so long? I reckon Celestron thinks you will power the CG5 from the cigarette lighter receptacle in your vehicle. In truth, everybody I know of uses a battery at the scope. Campers, this is one power-hungry mount, and running it off the battery in your car is a recipe for being stranded at the dark site on a cold winter night. Scopestuff sold me a nice coiled cable of just the right length.

Did my little fixes make the CG5 perfect? No. It’s hardly that, but what is? It is not the Rock of Gibraltar, but neither is its more expensive “inspiration,” the Vixen Great Polaris. With the C8 or a lighter tube on it it is very good under most conditions. Heck, it is quite good for visual work with a C11. Doubt that? Try it. My buddy Joe’s ASGT C11 has been a lot of fun to use over the years. With a set of vibration suppression pads and an improved (larger) accessory tray to help stabilize the tripod a smidge, the 11-inch is quite pleasant to use on the CG5.

The big draw is the go-to. It is crazy good. There is no doubt in my formerly military mind that it is every bit as accurate as my NexStar 11. And there is also no doubt in my mind that I saw more deep sky objects with my C8, Celeste, in the first six months she was on her new mount than I had with her the previous ten years.

Wasn’t all gravy, of course. The first time I had the scope and mount out where it was really dark, at the 2005 Chiefland Spring Picnic, I found the go-to could be a little crankier than that of the NexStar 11. The NS11 scope will usually perform perfectly despite its choice of alignment stars. The CG5? Not so much. When it picked a star a little too close to the horizon one night at the Picnic, I found Celeste was missing a few Virgo galaxies. Next night, I declined the stars the hand control offered, chose three that were better placed, and all was well.

Thanks to Celestron, that go-to problem did not last. Not long after I got my CG5, they came out with a new firmware rev that replaced the old Three Star Alignment with a much better Two Star procedure. How could two stars be better than three? Because, in addition to the two alignment stars, the newer software gives the option of centering up to four calibration stars that eliminate “cone error” problems due to mechanical misalignment. 

Only fly in the soup? The earlier CG5s--like mine, dangit--were furnished with non-programmable hand controls similar to those shipped with the original Celestron NexStar 5 and 8. That mean that if you wanted to try the new firmware, you had to pony-up about a hundred bucks for a new HC. In my estimation, however, it was well worth the price of admission. I don’t believe the mount has missed a single go-to since I bought the programmable model and loaded up the new firmware.

One thing I really, really liked and still like about the mount? Its polar alignment routine. While it would later be replaced with Celestron’s even better AllStar polar alignment procedure, which allows you to polar align on (almost) any star, the old method was simple and worked well. When you finished your go-to alignment, you’d tell the HC you wanted to polar align. It would then slew to where it thought Polaris should be given a perfect polar alignment. Move the mount in altitude and azimuth until the star was centered in the eyepiece, and voila! polar alignment complete. I don’t bother to do the procedure unless I’m imaging, but it is a real time-saver when I am.

Meade DSI snapshot with Celeste and CG5.
And how is the mount for imaging? With an “HC” polar alignment and good balance, it can surprise. Yes, it’s gonna show periodic error in the neighborhood of 30-arc seconds, but not many years ago that was considered outstanding performance. The CG5 proved to be good enough for me to do unguided 30-second subframes, yielding enough untrailed ones to stack into some pretty good looking images as images with the original Meade DSI, the camera I bought when I decided to give CCDing another go after my “unfortunate” experiences with a Starlight Xpress MX5.

Later, I did some guided shots with the SBIG ST2000 and found the mount could easily deliver 5 – 10-minute subs if I kept the C8 at f/6.3 or faster with a focal reducer, or used one of my fast APO refractors. I got some really cool shots with them, like the one of the Rosette below done with my 66mm William Optics SD. No, not every sub-frame would be perfect, but many would. Given the mount’s cost, you cannot beat that with a stick, muchachos.

Naturally, if you want to take pictures with the mount you need good conditions, as in no wind. With a strong wind blowing, you won’t get far even with video astronomy, as I found out one November down Chiefland way. Even the short 10-second exposures of my old Stellacam II were too much. The wind would blow and the stars would trail like crazy. Removing the dew shield helped some, but not enough. I will say the rig would have been useable visually on that night; I’ve done so successfully under similar conditions since.

What has changed with the CG5 over the last few years? Celestron did a fairly extensive update to the firmware in late 2008, adding the previously mentioned AllStar and some other new stuff you can read about here. Recently, they released a somewhat less extensive revision v4.20, which added selectable go-to slewing speed and not much else.

While Celestron hasn’t changed the mount much, there has been a major change in how I use it. The last several years, I’ve operated it with the NexRemote software far more often than with the hardware hand control. That fits in better with The Herschel Project. I can sit at the netbook computer and video display and do everything from there. Being able to use a wireless gamepad to steer the CG5/C8 is awful cool, too. It’s no surprise, then, that the CG5-C8 combo has become my rig of choice for The Project when I am doing video. It combines the excellent optics of Celeste, the light weight and good go-to of the CG5, and the convenience of NexRemote.

My CG5's Rosette.
Seven years down the road, how many problems have I had with the CG5? Other than occasional power problems caused by me running my battery too low, not many. The little power switch went bad a couple of years back. Always meant to repair it or replace it, but never have got around to that. I leave the switch on and power up and down by plugging/unplugging the power cable. Works fine. There’ve been occasional computer hiccups, but they have always been cured by doing a “Factory Settings” on the hand control, which flushes out the pore thing’s memory.

Is the CG5 forever, then? It should be—it is that good—but nothing is. I don’t have any inside knowledge, far from it, but let’s face it: the mount has been around for about ten years and is looking a little long in the tooth. It is also almost being given away these days if that means anything. It was over 800 when I got mine; you can have one for $699 now or even less. With Meade’s much more “modern” looking and “advanced” competition, the LX80, in the offing I can’t help but wonder if Celestron is clearing out inventory.

I hope not. I just don’t see how a bargain mount gets any better than the wonderful CG5. I’ve used mine heavily for seven years, done and lot of good work with it, and just love it. It’s a swell mount that's allowed me to get more out of my C8 than I ever dreamed possible. Best recommendation I can give? If my CG5 crashed and burned tomorrow, I’d go right out and buy another one. I hope that continues to be an option, muchachos.

Next Time: The Herschel Project Night 32

Having just bailed on the LX 80 I am going to go with the a new CG5 and C11 combo.

I do appreciate your honest commentary, and will of course blame you personally if I don't like it.

Such is the price of fame, Sir.
I have never used a CG5. Seems like a good, portable mount. Wish you had a CGEM Rod so you could give us an Atlas CGEM shoot off.
I almost bought a CGEM when they first came out, but I made friends with the Atlas and that was that. I still may pick up the DX version.
I bought a CG-5 a couple of years ago and have had no problems so far. It replaced the original mount on my 1986 C-8. Aligning usually is a chore but I can get decent GOTOs most of the time.
The CGEm is very powerful.So i want to bought CGEM.
I just bought a used CG-5 ASGT a couple of weekends ago as a tracking mount for my TV 85. Of course, we haven't had anything but completely socked in for the past 2 weeks on any night where I could get out so I can try it. It's heartening to read that you think enough of this mount that you'd buy another. I'm looking forward to forming the same opinion.
Hey Rod,

Somewhat off-topic question -- have you had a chance to try out the new iOptron Solar 60? It sounds like iOptron's competition to Snoopy, your mighty ETX-60.

I'm tempted to get one of these chaps for $399, but the ETX-80's are also starting to go on clearance for $240 or so (though I think they are rapidly going to become impossible to get, and parts availability might become a problem).

Would love your thoughts on this as a little travel scope to supplement the Somewhat Bigger Iron at home...

Hi Cathy:

I have not seen the Ioptron in the sure looks sweet. OTOH, after all these years Snoopy just keeps going and going and going. LOL. I suspect the Ioptron might manage higher powers a bit better.
Unk S:

BE SURE you get a set of Celestron's vibration supression pads if you intend to put an 11 on the CG5. Makes a big difference. As does a larger tripod spreader.
Thanks Rod. In the end I decided that the ETX is likely to be a very refined product (within the limits of its price point) after all these years, while the iOptron still seems to have some rough edges based on reviews.

I've just ordered the backpack version of the ETX-80. Fun times ahead.
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