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One of the most influential and iconic amateur telescopes over the last 13 years is Meade’s 90mm ETX Maksutov-Cassegrain. While the telescope has gone through many changes since its introduction (none more drastic than the 1999 introduction of GoTo-equipped models), thousands of the original single-axis drive, EQ fork-mounted model first rolled out in 1996 are still in heavy use by devoted fans of this minute powerhouse. The original ETX is also easy to find on the used market. The ETX is something of a divisive telescope; some users have elevated it to a cult status (although not quite as cultish as fans of the Questar), while others heavily criticize some of the scope’s more idiosyncratic design features.
When I got the opportunity to put the classic ETX through its paces, I was left with a mixed impression of the scope. I can understand both viewpoints as well as why there is such controversy over this tiny and quirky telescope.
To begin with, the ETX has two abundantly obvious design flaws. The tiny, optically questionable finder hugs so close to the tube that it is almost impossible to look through. Newer computerized models have a higher profile red-dot finder, but the original ETX’s finder is completely unusable. It is no surprise that the most popular aftermarket finder for the ETX is the Rigel QuickFinder, due to the Rigel’s high tube clearance. Additionally, the focus knob is difficult to reach if the telescope is pointed near zenith. This is much more of a difficulty if the telescope is being used in Altazimuth mode. In Alt-az mode, if the scope is pointed higher than 45 degrees the focus knob is awkward to reach between the fork tines. The telescope’s lens cap is made of anodized aluminum and screws on to the front of the tube. While this gives the scope an air of quality, screwing and unscrewing the lens cap in the dark can be an awkward undertaking. If the lens cap becomes cross-threaded you may be in for a world of pain. These design deficiencies, combined with the immense popularity of the scope, led to the birth of a unique cottage industry within the larger astronomy equipment industry; one of companies (especially JMI) devoting entire divisions to making aftermarket accessories to improve the experience for ETX owners. With a few of these aftermarket improvements in place, the ETX eventually becomes a complete, easy-to-use instrument. To many fans of the instrument, the ETX is largely a jumping-off point for extensive customization. As it is, while not quite on the level quality-wise, the ETX is not nearly as idiosyncratic as the iconic Questar, the telescope the ETX was clearly inspired by.
Optically, I can certainly understand the massive appeal of the ETX. The unit I tried out star tested very well. The only discernible optical flaw was a minute trace of spherical aberration. The optics were perfectly collimated, and views were bright, sharp and of very high contrast. The relatively small central obstruction (for a catadioptric) meant that higher-magnification views of the moon and planets were very pleasing, and the ETX provided decent views of bright deep-sky objects as well. Optically, this is an excellent “general purpose” instrument. While the optics are not up to the impossibly high standard of the Questar, they are of very high quality and slightly better than comparably sized Chinese Maksutovs from Synta.
The mounting, when used on the included table-top tripod, can be pretty wobbly. When mounted on a sturdy, full size tripod with a wedge, the fork mount is quite stable. When using a flexible focus-knob extension, focusing becomes a less vibratory experience, and also much less awkward giving the previously mentioned inconvenient placement of the focus knob.
In the final analysis, the telescope is exactly what many people buy it for in the first place; an optically excellent, moderately priced telescope which can be easily customized to ultimately create a highly personalized instrument. For those looking for a complete and easy to use instrument right off the bat, a used ETX-RA may be a telescope you want to avoid. These are worth seeking out on the used market as long as you know what you are getting into.