Sunday, March 06, 2011


Curing Charity

Charity Hope Valentine and I have had a beautiful relationship since she came to live with me at Chaos Manor South five years ago. Which doesn’t mean we haven’t had our ups and downs. What romance hasn’t? Now, before y’all run off to Miss Dorothy to tattle on Uncle Rod for his indiscretions, remember, Sweet Charity  is my ETX 125PE.

What’s Unk doing with an ETX, anyhow? This time of year one comes in awful handy, muchachos. In the spring I can awake on Saturday morning to beautiful blue skies, the weather reports can insist “clear tonight,” and by Sundown be chased off the Possum Swamp Astronomical Society’s observing field by vicious thunderstorms. I need a scope that, if not exactly qualifying as a “grab ‘n go,” can at least can be disassembled and back in the car in a hurry.

Maybe even more importantly, one portable enough to encourage me to give the dark site a try when it doesn’t look like there’ll be much chance of seeing anything. Some of my best runs, in fact, have been on nights that initially looked hopeless. A scope with decent performance, but which is not a pain to set up and tear down is a must.

Many, many telescopes fill the above bill; everything from the Orion StarBlast to an 8-inch Dobbie. I’m rather picky when it comes to my uber-portable scope requirements, though. I want a telescope with a drive. I want a telescope with computerized go-to. I want good optics. And I want to be able to sit comfortably to observe.

When I began my quest for a quick-look springtime scope, the one that seemed to best satisfy my needs was the NexStar 5. 5-inches is enough aperture to show lots and lots of stuff while remaining portable, if not always one-hand portable, and the C5 in all its incarnations has had a great reputation. Alas, at the time the C5 was on one of its periodic hiatuses and out of production. Second choice? That was easy: the ETX 125.

While an ETX wasn’t my first choice, it was undeniable the scope had her charms. Above all, the ETX is famous for world-class optics. Despite a large baffle around the aluminized secondary mirror “spot” on the corrector’s interior surface—the ETXes use the Gregory Maksutov design—that increases the size of the central obstruction, the little scopes, and especially the 125, exhibit outstanding contrast. I’ve pitted Charity against a C5 on several occasions, and the MCT has always pulled ahead of the SCT at least slightly on all objects, delivering superior image sharpness and contrast and better looking stars at the edge of the field.

Tain’t no such thing as a free lunch they say, and you pay for the ETX’s advantages in several ways. First, while, yes, the images are slightly better than those in a comparable SCT, you give up field. The ETX has the slow focal ratio of f/15, meaning a 25mm eyepiece yields 75x, about what it would in an 8-inch f/10 SCT. Wide field eyepieces help open up the 125’s view, but it will never be a telescope for expansive cosmic vistas. How about a focal reducer? One might help a little, but the 125’s small diameter baffle tube causes vignetting with eyepieces longer in focal length than about 25mm when used with one of the ubiquitous .5x reducers.

There’s also the ETX’s mount. The initial 5-incher’s fork was, to put it mildly, insufficient. When Meade designed the 125 all they did was scale up the ETX-90’s mount. Alas, the plastic fork arms that were OK with a 3.5-inch resulted in a wobbly telescope at 5-inches of aperture, and at f/15 the last thing you want is the wobbles. Thankfully, Meade, for once, rectified their mistake and redesigned the fork. It still looks like plastic, but is metal inside where it counts. Still, the ETX’s build quality, both mount and tube, is heavy on the plastic and at least looks flimsy and not ready for the long haul.

All in all, though? Acceptable. The ETX 125’s drive is OK, but is prone to backlash and is certainly not what you’d want for long exposure imaging. On the other hand, who wants to take long exposure images at f/15? Tracking is fine for visual use. Its go-to accuracy is also more than good enough. In addition to comparing the optics of the ETX and the C5 (a NexStar 5i), I compared their go-to capabilities. When carefully aligned, both scopes usually placed a target object somewhere in the field of a 25mm eyepiece, but the ETX did so a little bit more frequently than the NexStar, which seemed to get lost in some areas of the sky despite its shorter focal length.

Not that the ETX exactly inspires confidence when you send it on a go-to. When the telescope is slewing at full speed on both axes, the sound resembles, as I’ve said more than once, “weasels with tuberculosis.” Charity gets to her targets, but the noises she makes make you wonder whether she will. Sometimes I expect springs, bolts, and smoke to fly out like in an old cartoon.

Back to the story of Rod and Sweet Charity. When she arrived, just ahead of the financial crash of the Florida scope dealer I bought her from, Scopetronix, I was impressed. Fresh out of the box, she was a pretty little thing. I had opted for the ETX 125 PE, the no longer produced “Premier Edition,” and she sported some cosmetic and functional changes and improvements compared to earlier 125s.

Most noticeable was her tube. Rather than the subdued blue of earlier ETXes, the PE 125s, and the smaller ETXes as well, had their tubes silkscreened with color astro-images. In Charity’s case, the North America Nebula with its profound pinks and reds. I’ve been told she’s “gaudy” and “tarted up,” but I think she is beautiful. Hell, the renowned Questar 3.5’s tube is emblazoned with a Moon map which looks just as cheesy/gaudy to me.

More important—all telescopes, like all cats, are black in the dark—were Charity’s functional improvements. ETXes, all of them, the 90, the (now discontinued) 105, and the 125, were originally equipped with near-useless tiny finder scopes. With the PE edition, Meade changed to a much more practical zero-magnification red dot finder. But the red dot finder on Charity was more than just a finder. This was Meade’s once-trumpeted LNT (Level - North Technology) finder.

Charity’s LNT housing incorporated an electronic level and compass in addition to the finder itself. What for? Given the correct time and location, the compass and level allow the PE telescopes to align themselves, not unlike Meade’s LX200 GPS SCTs. As long as the scope is used close to the latitude/longitude set in the Autostar (within 60 miles), all the user has to do to get going is place the telescope in a simple “home position,” turn on the power, and center two stars when told to by the Autostar 497 hand control. The LNT unit also houses a button cell battery to keep date and time current.

First light with Charity in the backyard, I plunked scope and tripod down, roughly leveled her, and flipped the o-n/o-f-f to o-n (I had previously set the time and entered my geographic coordinates). Miss Valentine did a little dance, finding north, tilt, and level and headed for the first of two alignment stars. I centered the stars as requested, and the little scope claimed she was aligned. Huh! We’d see about that.

Surprise! Every object I asked for on that first night, horizon to horizon, was somewhere in the field of the 26mm Meade Plössl I found in the box with the scope (also in the box was a cute Meade-blue tripod bag that immediately commenced to coming apart at the seams). I was impressed, yeah. Well sort of.

As you-all know, I name my telescopes. The C8 is “Celeste,” the NexStar 11 GPS is “Big Bertha,” the 12-inch Dobsonian is “Old Betsy,” and so on. So why did I name my ETX 125 after Broadway’s hapless heroine, Sweet Charity, Charity Hope Valentine?

After a little use I realized the telescope was on the neurotic side. Some nights, Charity would behave herself beautifully, navigating to dozens of objects and showing them off as well as any 5-inch telescope possibly could. Then there were nights when she couldn’t find pea-turkey till I’d run through the “Drive Training” routine in the Autostar (which helps the computer deal with the mount’s backlash). And strange nights when her go-tos became progressively farther and farther off as the evening wore on. Or her Autostar didn’t want to boot up at all, freezing until I cycled power.

Thankfully, the above symptoms were fairly rare, with me putting a generous amount of hazy springtime-night viewing hours in with my new telescope. Even when she was at her best, though, the weird sounds she’d make when going to her go-tos would get me to wondering if she were about to collapse in a self-pitying heap like her namesake. To sum up, Charity was and is a telescope that inspires love but not always confidence.

This feeling was not helped by Meade’s assembly faux pas. When I bought Charity, Meade had recently moved their ETX production to China, and apparently all the bugs assembly and QA wise were not even close to being exterminated.

Two of the three faults Charity exhibited out of the box were cosmetic in nature and nothing more. One of the Meade labels pasted to the tripod was on upside down. I guess the folks at the plant in China had trouble with Roman letters. I pried it off and flipped it 180 degrees. Also, the RA setting circle was misapplied and stuck to the base so it could not be adjusted. I knew I’d never use the dang thing, but I fixed it anyhow.

The third fault was a serious one. In my initial uses of the telescope, I noticed some odd reflections in the field when I was pointed at a bright planet or the Moon—especially the Moon. Not being overly experienced with Gregory-design MCTs, I wondered if the donut-shaped glow I was seeing was an artifact of the design or whether Meade’s implementation of it had problems.

Turned out to be neither. One day I was shooting pictures of Charity for my book, Choosing and Using a New CAT. Looking at my girl’s (ahem) rear end through the camera viewfinder gave me a new perspective: “MEADE, YOU DAMNED SUCKERS!” It was now obvious Charity’s eyepiece tube had been screwed into the rear cell crooked.

Was I in a snit? You bet. I assumed they’d likely have either ruined the threads by cross-threading or would have glued as well as screwed the eyepiece tube into place. Sending Charity to Meade service department Hell was not something I looked forward to, but what else could I do. Unless…

Rummaging around, I located a strap wrench, a small one. I fastened that around Charity’s eyepiece holder and turned gently in counterclockwise and then clockwise directions. Almost before I knew what had happened, the tube had snapped into place and was now perfect. Pointing Charity at the fat Moon hanging in the sky showed the weird reflection had been banished. Whew!

So, Uncle Rod and Sweet Charity lived happily ever after? Not exactly. Well, almost. She has provided me plenty of viewing pleasure over the years, but she can still be a pill. For example, the LNT works great till its battery dies. Meade claims it will last for years, but a year is the longest I’ve ever got out of one. When time comes to change this button cell, you are in for some real fun.

To get at the battery, the finder’s small screws and springs have to be removed (do not even think about changing the cell in the field), and extreme care must be taken not to break the thin wire that runs between the top and bottom of the LNT finder. When you get battery in and the LNT back together, the fun’s still not over. When the button cell is removed, Charity becomes badly confused and several “calibration” routines have to be redone. You also have to realign the finder.

And yet…and yet… Despite her foibles, I will not hesitate to say Sweet Charity has done a good job since I fixed her factory-inflicted defects and learned her quirks. It seemed that way, anyhow, till her Autostar hand controller began to go south.

Like most go-to telescope hand controls, Charity’s Autostar is equipped with a rubber membrane keyboard. In this design, rubber keys have disks of conductive material on their reverses that impinge on contacts on a circuit board when keys are pressed. This can work fine, but it does not work fine with the Autostar. Not for long. Apparently, Meade uses the most inexpensive keyboard of this type it is humanly possible to produce.

The practical effect of Meade’s stinginess is that the keyboard is not overly responsive when the Autostar is new and gets progressively worse. This doesn’t just affect the ETXes, but all Autostar and Autostar II telescopes. The last time I had Charity out to the dark site, her Autostar had become nearly useless. Oh, all the keys still worked, but I had to mash them as hard as hell to get them to register. Including the direction keys, which made drive training, which—wouldn’t you know it?—Charity demanded once again, derned near impossible.

What were the alternatives? I reckoned I could either buy a new Autostar (about 150 greenbacks) or put Charity out to pasture and buy a NexStar 5se. That latter idea had some appeal. I have always admired the C5, though I’ve never owned one, and the current orange-tube NexStar 5se has good optics, a build quality superior to the ETX, and improved go-to accuracy. But sometimes a telescope is more than the sum of its parts. Charity had become my friend and it hurt my heart to think of relegating her to the dusty depths of Chaos Manor South’s Massive Equipment Vault.

I decided to think things over for a while and do some research. Googling “ETX” and “Autostar” and “Keyboard” gave me a third alternative. I learned that rubber computer keyboards are repairable, and that Numero Uno scope gadget salesman, Jim Henson of, had a kit designed to restore Autostar responsiveness.

I’d normally be skeptical of something like this, even though Jim is one of the most honest and dependable vendors in the business. I’ve been burned too many times by “miracle cures.” A little more research, however, led me to believe this was one time the snake-oil might work.

The kit from ScopeStuff was not designed by some fly-by-night telescope maniac in a dusty garage; it was a common item sold by electronics vendors for repair of all rubber membrane keyboards (mostly in TV remote controls these days). The price, whether from Jim or electronic giants like Jameco, seemed a little high, just over 25 bucks, but that was sure less than the price of a new Autostar. I got out my credit card.

Thoughtfully, Jim has posted links to instructions for repairing the ETX keyboard using the kit, so I was able to study and prepare myself. The procedure looked simple. Take the Autostar apart, remove the keyboard, and clean the little black disks on its reverse with denatured alcohol and Q-tips. Do the same to the contacts on the printed circuit board beneath the keyboard. When everything is squeaky, mix the two epoxy-like components that constitute the kit, paint the keyboard disks with the semi-liquid goop, let set for 24-hours, reassemble the Autostar and—supposedly—voila!

In usual ScopeStuff fashion, the keyboard repair kit arrived sooner than I thought it would. I set it aside until Friday afternoon, when I’d do the deed in preparation for the Saturday night New Moon run at the PSAS dark site.

When I got home Friday, I got to work. Step one, disassembling the Autostar, is easy for those of y’all with a little electronics repair experience. Opening it up doesn’t take experience, just a small screwdriver, but getting the insides disassembled does.

After you unscrew the four small Phillips screws that hold the Autostar together and separate its two halves, one of the first things you’ll notice is a funny-looking rectangular piece of white plastic, a light diffuser, inserted behind the display. Remove this diffuser and set it aside. The Autostar’s LED display is attached to the circuit board with a thin ribbon cable. Unless this cable is disconnected, it’s a little difficult to get the keyboard out. This is where experience comes in. If you’ve done some work along these lines, there is nothing to fear.

The cable goes into a socket on the back side of the Autostar’s “motherboard” and is held in place with a plastic clip. Gently disengage the ends of this clip and the ribbon cable will slip out of its socket. You can then remove the board from the front half of the Autostar enclosure. Set the circuit board aside and remove the keyboard. There is nothing to that. The membrane keyboard is held in place by the circuit board, and with that out of the way, the keyboard just slips out.

Does the ribbon cable look scary? If so, leave it connected. Gently move the circuit board up and out of the way and slide the keyboard out without disconnecting the cable. Just be careful not to stress this flimsy ribbon.

Keyboard in hand, begin the repair. Start with the denatured alcohol. This should be 91% strength stuff, not 70% rubbing alcohol. The stronger solution is readily available in drugstores like Walgreens and Rite-Aid. Dampen a q-tip and swab each of the black disks on the back side of the keyboard. The q-tip will come away dirty. Trash it, wet another with alcohol, and continue until a q-tip comes up mostly clean. I initially thought this black substance was oxidation, but I now believe it to be some sort of stuff Meade applies to the disks to improve contact/conductivity. If that is the case, it didn't work. It is also very hard to remove; just get as much as you can off the disks. I went through half a box of q-tips before one came up halfway clean.

When you are satisfied with the keyboard’s disks, move on to the printed circuit board. The side of the circuit board that faces the keyboard is studded with numerous silver-looking contacts, one for each keyboard key/disk. Dampen a fresh q-tip and swab the contacts. Don’t bear down and don’t drown them in alcohol. A quick wipe with a moist q-tip is all they need. When all cleaning is complete, it might not be a bad idea to dust off both circuit board and keyboard with canned air. Hold the can upright and about a foot away to avoid spraying propellant into the Autostar’s guts.

Everything up till now was preparation for the real job, coating the keys with the liquid that came in the kit. If you haven’t opened the kit, do so now. Inside are one small bottle, one larger container, a small brush, and a mixing stick. Pour the contents of the little bottle into the larger container and mix vigorously for one minute.

After this epoxy-like gunk is mixed, you have, according to its makers, 72 hours to use it before it sets. My advice? Do not mix it until you are ready to apply it. 24-hours later, what I had left over was mighty thick. There doesn't seem to be much of this stuff even when the two components are mixed, but so little is needed to repair the Autostar that one batch will easily do four or five HCs—at least. If you have buddies with cranky Autostars, share the wealth and do several at once, maybe splitting the 25 buck cost among you.

Hokay: time for rubber to meet road. Paint the mixed goop on each black disk’s face in a thin layer. Do not glop it on and avoid getting the stuff between the keys or anywhere else. I found it easy to do a neat job with the small included brush, but I amuse myself on cloudy evenings by assembling and painting plastic scale-model spacecraft. If you are inexperienced with painting small objects, don’t worry. Any of the gunk that gets in places where it shouldn’t be is easily scraped off with a toothpick—after it dries. In case you are wondering, NO, YOU DO NOT PAINT THE CIRCUIT BOARD CONTACTS! THE GOOP ONLY GOES ON THE CONTACT SURFACES OF THE KEYBOARD’S BLACK DISKS.

Now the hard part, waiting 24 hours for the fix-stuff to cure. Don’t even think of reassembling the Autostar or fooling with the keyboard in any shape, form, or fashion until an entire day has elapsed.

When the long hours have passed, reassemble the Autostar, beginning by slipping the keyboard back in place. If you detached the ribbon cable from its connector, gently reinsert it and snap the retaining clip in. Seat the circuit board over the keyboard and replace the white plastic light-diffuser over the LED display panel (the curved side faces up). Snap-on the back of the Autostar, screw-in the screws, and that is it.

Moment of truth. Fetch the telescope, plug in the Autostar and the battery, and power her up. If the display lights and shows its usual verbiage, you can be assured you haven’t, screwed up that pea-picking ribbon cable. But how well did the repair work?

I won’t say my hands were trembling as I turned on the ETX, but I was a little apprehensive. This snake-oil treatment seemed too easy. OK. One of my prime offenders had been the “Mode” key. As soon as the Autostar booted up and read “Press Align to align, press Mode for menu,” I mashed “Mode.” But I didn’t mash it like I’ve had to lately, with every bit of what little strength I still retain. A gentle push and…the key responded just like it is supposed to. I experimented with the other keys and every one of them, including the direction keys, thank god, worked just as well as they had on day one. In fact, I was of the opinion that all the keys were considerably more responsive than they had been out of the box.

Naturally, I was anxious to try Charity on the observing field. Unfortunately, Saturday was one of those days that tease. Clouds at times, blue skies at times. The cotton-picking Weather Underground had started out predicting “mostly cloudy tonight,” but by mid-afternoon was saying “mostly clear.” Yay! Not that I was completely convinced I’d actually see anything, but I figgered it was at least worth a shot. If the clouds rolled in, I could have Charity back in the Toyota and be headed for home in ten minutes.

As Sunset approached, I became more and more optimistic; it did seem to be clearing. SUCKA! When I hit the road for the dark site, I couldn’t help noticing a band of clouds hugging the western horizon. Rut-roh. Most weather fronts here travel from west to east. Oh, well, I kept a stiff upper lip and kept going. Twenty-five miles later, I wasn’t just seeing clouds in the west; they were everywhere. By the time Charity was unpacked, we were completely socked-in. At least I could do the dadgum Drive Training and see what was what after that.

Drive Training is critical for the ETX’s go-to performance, but is easy enough to do. Sight a terrestrial object (which seem to yield better training than celestial ones) and select “Drive Training” from the Autostar’s “Telescope” menu. The reason I’d waited until I could get to the dark site to do this training is that there are perfect targets there, the illuminated runway lights of the air-strip next to our observing field.

Centered a distant light, hit the “go” button, and Charity slewed to the left. I used the appropriate key to re-center my target. Miss then slewed to the right, and I again placed the light back in the middle of the crosshairs. Altitude training was next, with Charity slewing up and down and me re-centering when she stopped. One thing I noticed right away: how much easier it is to precisely center the target when the direction keys work like they should.

Looking up from the scope, I saw that post-sunset the clouds had got thicker rather than thinner (I’d convinced myself that these must be the sort of clouds that always disperse at sunset). I played around with the Autostar a little, running through its various menus, getting information on objects I couldn’t see and assuring myself the key problem was banished.

I was curious and still am about how long the keyboard improvement will last, but what I’ve read and heard indicates “forever.” The kit’s documentation says repaired keys have been tested for thousands of keystrokes, and I have not heard anyone who’s done the repair say their keys have gone south again.

Done playing with the Autostar, I waited on the field with my friend George, my only fellow club member who’d been optimistic enough to join me, to see if we were well and truly skunked. By 7:30 p.m., we threw in the towel. There’d been a sucker hole once in a while, but not enough of one to allow me to get Charity aligned. Thems the breaks, breaks you are used to or soon will be if you are a member of that hardy band who call themselves “amateur astronomers.”

Next Time: If it was clear this past Saturday, Charity ran the Messier Marathon. Yeah, I know it’s a mite early for that, but so what? It ain’t like Unk will be able to stay awake till dawn to do the whole big thing, anyway, now is it? If it was cloudy? Well, who knows? I will think of something. I always do. What can happen?

Uncle Rod, your descriptions sure do have a way of bringing the reader right there disassembling the controller and working out backlash settings. I love to read your posts and the valuable insight you experience brings, thanks, Jason Herin.
My ETX started having fits several months back and ended up on a shelf in the garage. You may have just inspired me to dust it off and give it the benefit of the doubt.
Thanks Uncle Rod.
The Autostar controller on my 2003 LX90 finally bit the dust two months ago. Besides having to squeeze the life out of it to register a keypress, it had been dropped on the concrete floor of the garage by the little ones too many times and refused to boot at all. I thought I ordered an identical replacement unit, but what came in the box was the new fangled "AUDIOstar" model that talks to you out in the field when you least expect it.

I'm pleased to report that the new style handbox is _amazingly_ responsive, it feels just as good as my Nexstar 11 controller and is much better than the original unit that came with the LX. I'd never so much as upgraded the firmware on the old unit, and never trained the drives - the pointing accuracy on the original was that good. This one is even better. If you ever have to buy a replacement it is well worth it.

Good luck with Charity next time Rod!

--Robert Harris
Rod, when you replace the battery in the LNT you must do:

Drive Training
Calibrate drives

is that right? Also have you had an experience deforking one of these ETXs and placing them on another mount?
Yep...that is right. They are fairly easy to place on another mount, but you will need tube rings to do it, since the viewing angle of the built in diagonal can't be changed. I don't think I'll be doing that unless Charity throws a gear. In that case I'll probably use her on the mount of the Nexstar 5se I will replace her with--god forbit. LOL!
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