Meade DSX-90 OTA

1.0 Frustrating Mak-Cass Scope

Sharp image, good contrast, good on planets and Deep Space Objects.

Double image and image shift make this scope unusable without aftermarket visual back and focuser.

I purchased a Meade DSX-90 90mm Maksutov Cassegrain optical tube assembly to compliment my short-focus refractor. With a 1250mm focal length and an f/13.8 focal ratio, I thought it would be perfect for high-magnification views of the planets.

Considering the scope’s small size, this was a heavy, solid-feeling piece of equipment. While the front of the tube is thick aluminum, the back end holding the focuser, eyepiece holder and “Flip Mirror” was made of plastic. This use of plastic in many lower-end Meade scopes has made me hesitant to purchase these scopes in the past.

I’m aware of Meade’s spotty quality control issues so I’m hoping my scope is not representative of the entire line. To put it mildly, this scope soured me on Meade scopes and Mak-Casses.

Using the scope with an eyepiece in the 1¼-inch eyepiece holder provided a distracting double-image, bad enough that getting the image to a focus was very difficult. With an eyepiece holder and diagonal mounted to the back of the telescope, this was eliminated, convincing me that there was a problem with the scope’s Flip-Mirror.

Once the flip mirror was taken out of the image path I was impressed with the scopes sharp, high-contrast images. Using a 10mm Plossl for magnification of 125x, Saturn was bright and crisp, clearly showing the Cassini Division and banding on the planet. The difference in the brightness between the A and B rings was easily discernible. M42 was beautiful with a 21mm eyepiece at 60x, showing lots of detail out to the “bat wings” and the “shark’s mouth” clearly stood out against the nebulosity. The Trapezium was easily resolved at high power. Viewing at high power, however brought out another problem I had with this scope.

My Meade DSX-90 90mm Maksutov Cassegrain suffers from a phenomenon common to cheaply made Cassegrain telescopes known as “Image Shift.” The long focal length of the scope gave it a narrow field of view to begin with. If the focusing knob was turned in either direction, the image moved enough to sometimes throw the object being viewed completely out of the field of view. This can be resolved by mounting an aftermarket focuser to the scopes back but how much aftermarket accessories should a scope need just to make it usable?

In conclusion, my frustrating experiences with Meade’s DSX-90 90mm Maksutov Cassegrain OTA left me with such a bad impression that I cannot recommend it. I can only hope that this scope was the product of bad quality control and is not typical of the line.