Pros: Compact, lightweight
Cons: difficult to use, poor quality plastic mount, drive noise
The ETX-90 was hailed by Sky and Telescope and many others when it first appeared as the dream telescope everyone had been waiting for. It looked really cool. It looked like a new version of the legendary Questar 3.5" Maksutovs which, 50 years after they first appeared, still have no equal. Unfortunately, the plastic mount and telescope rear cell combined with poor layout largely compromise this design. More general information on getting a telescope is in my article on Picking a Telescope.
The Questar is $3500 or more depending on what version you get, but is packed with neat features like a compact beautiful polished aluminum driven fork mount. These telescopes have many built in features like small flip mirrors which allow a camera to be attached to the back of the telescope. But, they also have another feature where the mirror has another position where the view is diverted out the bottom oof the telescope to a mirror which makes the main eyepiece work as a finder scope. The Questars also have lots of neat features like included solar filters and flip up filters for the finder for solar viewing. But they are still $3500 and up.
Description and Usage
When the original ETX-90RA showed up, it was very sleek looking and compact, and had some specifications which indicated it might be something special. It was a small Maksutov on a fork mount with a flip mirror which allowed the user to have a camera attached while they were viewing. It had a small clock drive mount. It had that beautiful metallic blue finish. It looked really cool.
However, here is where the story takes another turn. The ETX-90RA turned out to be hard to use. The tiny finder scope mounted on the top left of the telescope is almost impossible to physically move your eye to a position to look though it. If you are left-eyed, as I am, you are essentially out of luck. The second feature causing usability difficulties is the long focal length. The telescope has a very narrow field of view, so an approximate fix on an object won't put it into the field of view- your sighting has to be really good.
The next problem is the mounts are all plastic, and too thin to prevent bouncing. The method for attaching it to a tripod is to screw in three screws into a flat plate on the base- with one hand because the other needs to keep the scope from sliding off. But these are mounting the telescope into the middlle of an unsupported flat plate in the base- this forms an ideal flexible spring, so the telescope bounces whenever you touch it.
There are also some other strange quirks. The telescope mount fork is so short that the telescope cannot be pointed anywhere near the southern horizon when it is set up for phootography in equatorial mode because it hits the mount's hub, first. Even at low lattitudes where I am, at 30 degrees North, the ETX-90 won't make it to the horizon. Secondly, a camera attached to it will hit if the telescope moves up to photograph anything near the north pole. As a result, the built in flip mirror and camera attachment are of dubious utility. On many of these telescopes, the flip morror causes the image to jump, anyway, so the photograph would not be where the viewer thought it was, anyway. And there are features which appear to be ridiculous- the lens cap screws on, so the user has to be very careful not to cross-thread it and has to take time to get the cap on and off as it squeekily turns.
So, the revolution the ETX (which incidently, was literally supposed to be an every-man's telescope) promised really didn't go very far. So, a new version was developed: the ETX-90EC.
The ETX-90EC has the capabilty to, with and additional $125 hand computer, become a Go-to telescope capable of pointing to a large number of pre-programmed astronomical objects as well as ones from Meade's web site or ones chosen by the viewer. This set of features prompted another round of hails for the perfect telescope having had arrived.
But, the telescope was still difficullt to use in a lot of ways, it still has to be attached to a tripod the same way, and has to be removed from the tripod to change its batteries. Worse, the pointing problem was still just as bad except now users found that even though it is possible to disengage the clutch and point it at what you can see is right there, but don't have a name for, this will cause it to lose its orientation, so the go-to feature is lost.
So, how is it as a telescope, anyway? The mount will automatically find things. Punch something in and it starts moving along with its plastic gears sounding like a toy car in a mall toy store. When it gets to the object, you can tell it has locked on when it starts making a sort of loud crunching sound. I haven't heard another make of telescope with drive motors as loud as a Meade's. The tracking sometimes looks a bit jerky until it settles down. Use as low a power and wide a field eyepiece as possible to get started with so your object is in the field of view.
However, there is yet another lurking problem here- though the telescope costs as much as an Orion 10" diameter Dobsonian reflector, the low light gathering ability of this telescope will produce a minimally recognizable view of what you are looking at. This telescope costs over twice as much as a Celestron C90, a comparable telescope, but doesn't do anything the C90 doesn't in the image, and in fact is in some ways inferior since it has a longer focal length and hence narrower field of view. After looking at a lot of different objects through ETXs, I can safely say the image is average at best.
Personally, I can't imagine the beginning astronomer these telescopes are marketed to feeling anything other than disappointement with the views. I have heard many people say "That's it?" when hitting some of the most spectacular objects in the sky. I expect the experience would be far more rewarding if they had bought more impressive optics with the money and began learning the sky, instead of splitting a limited budget between optics and a complicated computer controlled drive system. The 10" Dobsonian I mentioned won't automatically take you to M42- you'll have to look on a map and point it yourself- but the Dobsonian mount makes easy to do since all you have to do is push the tube in the direction you want it to go. When you get there, the view will be spectacular. With the 90mm ETX-90EC, it will automatically move there and track, but the view will be quite dim and lacking detail in comparision. There is no moment of discovery when it goes there for you, when you can say "I found the great nebula!" and know where it is in the sky forever after. With the ETX, a machine did it for you, took the gleeful moment of discovery from you, and gave you a mediocre view to boot.
Finally, there appear to be very serious longevity problems for this telescope. I know three people who have had the light baffle Meade glued to the inside of the corrector lens at the front of the telescope start sliding out of place across the mirror and down the corrector, thus ruining the image. This isn't where people have done something silly like leave a telescope in a hot car- it is just doing that in the living room. Secondly, the plastic drive train appears to wear quickly so the tracking does not remain true.
I find myself wishing Meade had spent more time on the telescope and less on peripheral equipment. A Questar has lots of neat components added- but they are all very high quality and the price reflects that. This telescope sacrificed quality and performance to add lots of poorly executed features. The constraints of the optics make the camera mount at the back worthless. The poor usability of the mount dooesn't make it an enabling feature. I would not recommend this to a new astronomer, or anyone else. I would suggest ignoring ads from any vendor telling you a certain piece of equipment it perfect for you. Find your local astronomy club's observing events and go to a couple of them. Don't give yourself a deadline based on a holiday coming up or something similar- the experience of viewing will tell you what you like, what to expect, and give you a feel for how what you really want to pay for.
The ETX-90EC promised a lot. Unfortunately, by trying to put everything in an inexpensive telescope, it does nothing well. A large number of poorly designed accessories doesn't make a mediocre telescope better.