Pirich's Full Review: Meade ETX-125AT (500 x 138mm) Telescope
The Meade ETX-125AT, like the rest of the ETX line, is a product with a lot of visual flash combined with serious flaws.
I have a correction to Meade's listing of 500X138mm for this scope: Meade has started advertising these as 138mm Primary Mirror telescopes. This is not the actual diameter of the telescope: the front corrector is 125mm. Nearly all catadioptric designs have mirrors larger than the aperture in them, and the aperture is the given diameter. This is misleading advertising in this case.
I've seen a lot of these and used them, but find a review of them is so hard to write. The combination of great ideas with lousy execution in this product makes reviewing it painful to me. They are sort of like a telescope version of the Hummer H2- they look cool on the outside and are priced like the good stuff, and then you go to sit in it and nothing in it makes sense. They look really great from 10 feet away, and the fit and finish look great. But inside, they have plastic mounts with fragile belt drives that sound like cheap RC cars while they are slewing. And this comes at a price higher than its main competitor, the Celestron NexStar 5SE (Successor to the NexStar 5i). So, though I generally do not do direct competitor comparisons, after another observer plopped his ETX-125AT down next to my C5 at a Star Party at the Whipple Observatory, I had a chance to do a direct comparison and view other people's reactions.
Background
The ETX series telescopes from Meade began wit a little 90mm Maksutov around 10 years ago, apparently inspired by the superb Questar Standard 3.5" (89mm) Maksutov, which has been in production over 50 years, now. The similarities to the Questar were the high Focal length Maksutov Telescope combined with an optical transfer box on the back end with a flip mirror to allow an eyepiece and camera to be installed at the same time.
This is where the two designs diverge, though. The Questar has a few other built in features, such as a barlow and a finder in the bottom, and is all metal with absolutely superb workmanship and optics. Then again, this 3.5" diameter telescope sells for $4250 for the base model, and just adding a clock drive to its matching twin arm fork mount takes it to $5000- and at this price, everything else on the market is a cheaper option up to about 114mm in diameter. Though I have used these and do acknowledge their superb manufacture, the real niche is how compact and slick they are, and the unparalleled level of suport the manufacturer gives. And, their scopes are beautiful with their polished fork mounts and star maps engraved right on the optical tube. But even with a small forest of scopes I have, just one of these would cost more than all of them together.
In comparison, the Meade just looks a bit like an internet age version of the Questar. The mount is black plastic, as is the entire back end of the telescope. The first ETX series scopes only had a clock drive, which was later replaced with the Meade Autostar guidance system, which is now in all of their computer guided telescopes.
It may sound harsh, but perhaps the most telling thing about the ETX series is the general lack of output from them. Fairly rarefied telescopes such as the Orion 80ED refractor exist in much fewer numbers, but have generated a comparitively enormous quantity of high quality images.
Description and Usage
The ETX-125AT is a larger version of the ETX-90, at just under 5" in diameter, and really does look like a scaled up ETX-90. Like all Meade products, the ETX-125 has purposeful and bold lines in its outer form which seem to speak of confident capability and superb craftsmanship. In many ways, this is similar to a movie prop; it may look great, but it doesn't have much going to back that up. Like the 90mm version, this telescope has a plastic twin fork mount with a large drive base which attaches to its tripod at the center of a plastic plate. This feature is why even a light brush of your fingers on the focus knob sets the telescope vibrating for 10-15 seconds. The telescope is very crowded and compact in its build, with the fork arms just allowing enough room for the optical tube between.
Other features reveal themselves to be workarounds to a slick looking but otherwise flawed design. The finder scope, for example, is bent 90 degrees just to make it possible to look through it, but this makes the usual technique of sighting along the tube to get in the ballpark of an object impossible (the original ETX had straight through scopes where it was impossible for a human eye to be brought near them for much of the telescope's range of motion). Meade has now added an optical reflex sight to work around the problems cause by the right angle finder. In a way, it seems amazing how scaling up the ETX-90 design by close to 50% can still yield such a restricted and cramped feel, where getting to the focus knob means having to fold your hand to a point so your fingers can move past the fork arm when the scope is elevated. This tight arrangement and dual set of finders on top also means no form of piggybacking other equipment is very practical.
In comparison, the mount and drive system for the Celestron NexStar SE series have a single arm. Thanks to the mount's stiffer metal construction, the damping times for vibration are much faster, at around 1.5 seconds. The other effect of having one arm is the architecture of the mount is literally more open, where most of the scope is away from any obstruction and getting to accessories, the focuser, or finders is very easy. These later mounts also have one very nice new addition- the connection to the mount is a dovetail clamp, so you can slide out the tube which came with it and install another telescope, such as a small refractor or Maksutov or a camera at will. This configuration is a bit taller in absolute size, but the trade-off for this is usability.
The optics in the ETX-125 themselves are also surprisingly disappointing. The Maksutov design was developed with ease of manufacturing as a primary goal. And yet, the images I have seen through four different ETX-125s simply do not support the sort of extremely sharp high contrast views the design data says they should produce. Stars in these scopes have ragged edges and a precise focus does not appear to exist, implying there are errors in the mirrors. Given its larger central obstruction, the image in the Celestron C5 should be somewhat lower contrast than this scope, because it produces a bright diffraction ring on point objects. But in two hours of people walking between one and the other looking at the Orion Nebula, the Pleiades, and Double Cluster, they kept commenting to other family members, "Wait, come see it in this one!" as they pointed at the C5. I felt bad for the fellow who had brought the ETX-125 along, and a little more so when they asked us how much the two scopes had cost.
Photography
The back of the telescope is a large plastic housing with a port in the top for an eyepiece and a port in the back for a camera to attach to. The main difficulty is the small geometry inside the fork arms, which means getting to the focus knob around a camera is practically impossible, and most camera setups are in danger of bumping into the mount arms if the object is in the northern sky. In an inexplicable bit of strangeness, the drive base has a circular shelf on the drive base which sticks out at a larger diameter (close to an inch) right where the rotating porion meets the stationary portion. This not only constricts an already crowded setup, but it also is what the optical tube hits if you try to look at anyhing near the southern horizon. So, while the scope can be aligned in an equatorial setup for photography, in practice the mount has several large defects, which, combined with the excessive vibration from flimsy construction, are likely the main reason why there are so few deep space photos taken through these.
A secondary fault in this area is the focusing mechanism. I have used five C5s at this point, and the moving mirror focusers in all of them have two features in common: First, the image does not shift when reversing direction. Second, there is no backlash or dead space when reversing. This had made them very easy to get to a precise focus quickly, since you can roll back and forth across true focus until you know precisely where it is.
The ETX-125 has more mirror movement than even large 8" diameter Schmidt Cassegrains. The focuser is attached to a tiny knob which actually unscrews out the back of the telescope on a thin aluminum arm, which itself has a little bit of play where it will wiggle back and forth.
For the other mechanics, the barrel of the telescope is one of the handfull of metal parts to be found, as is the forward cell for the corrector plate. The lens cap is a scaled up thread-in design, which I personally can't stand, since when the scope is at 25F, your fingers are starting to go numb, and you're tired, having to engage fine thread on something 5.5" in diameter without cross-threading it in the dark is not fun. The secondary mirror is an alumized spot on the inside of the corrector, and at least on these I have not seen the common instance of the ETX-90 where the secondary's aluminum baffle starts sliding down the inside of the corrector plate with time. In comparison, the C5 scopes just have a snug slip-on lens cap on the front. Yeah, you still have to touch cold metal, but at least it's done quickly and there is no obvious way do damage it in the process.
Drive
The mechanical part of the drive is in keeping with the rest of the assembly. When VCR, tape player, and disk player manufacturers dropped belts from their drive systems in exchange for gears, the reliability had a night and day improvement. At the same time, the simple gear drive systems which have always been on Celestron telescope mounts are still widely in service after 30 years of use. And yet, belts are still in Meade's drives, even after they have become infamous for forcing replacement. But not only are these drives lacking reliability, they are also loud while slewing, with a very audible (lounder than conversational speech) whirring-grinding noise.
The big exception to everything else in the ETX-125AT is the Autostar guidance system. Autostar is such a radical departure from the rest of this telescope, I can't help but wonder if Meade would be more successful purely as a software company. The guidance system pioneered the practice of leveling the tube and pointing it north to start and alt-az alighnment, where the forks are upright. If you take the time to use a level and get it precisely pointed north, the alignment it starts from to get the precise stellar alignment will be exact.
Autostar's only quirks are a couple of minor things like being faster to find double cluster through the NGC number (oh, uh, yeah, that's ummm, NGC 794?), but it will go there, and accurately. Perhaps the most telling thing about these systems is when people re-use Meade hardware in other projects, it is an autostar system they re-use. More interesting than that is the fact the system can adapt to any mount- there is a menu where you can modify the drive ratio to match a worm gear Meade doesn't make. Top that off with the neat observing tricks NONE of the Celestron NexStars do, such as satellite tracking, and here there is something Meade did really well.
Conclusion
The Meade ETX-125AT is a sharp looking but otherwise disappointing product. For the amount of money, it really should perform a lot better. Although I have compared it with the Celestron C5/ NexStar 5 SE telescopes here, I am doing so simply because they are in a similar performance range. I would strongly urge anyone looking for a scope to look through some under the night sky, especially under conditions where styling will be less apparent than performance for making a decision.
The Meade ETX-125AT includes Autostar controller and compact field tripod.Features cordless motor drive for fully automatic tracking.The Meade ETX-124...More at OPT Telescopes
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