It would be interesting to do a side-by-side comparison of the ETX-80 and -90. From what I've seen through my ETX-60 and -90 the ETX-90 just gives much sharper images and much higher contrast. The challenge of the ETX-60, 70, and 80 is you can only do so much with a fast achromatic; CA and the accompanying loss of contrast and sharpness is unavoidable. For low power, wide field views the little refractor works fine, but it makes a lot of difference when you put all of the light where it belongs. The only problem I had with my -90 was I'd run out of light before I ran out of resolution making it difficult to use it at really high magnifications which is a big reason why I eventually picked up a 125.