#932 45° Erecting Prism:
If the ETX-90EC is to be used for extensive terrestrial applications, the #932 45° Erecting Prism is a useful accessory. Images through the 90° eyepiece-holder appear right-side-up, but reversed left-for-right.
The #932 Prism threads on to the telescope's photo port and presents a correctly oriented image as well as a convenient 45° observing angle. An eyepiece of any focal length (magnifying power) may be inserted into the #932 Prism. Note that the flip-mirror control must be in the "down" position for use with the #932 Prism.