Meade #933 Image Erecting Prisms for ETX-60, ETX-70 and ETX-80 Models all feature an internal flip mirror to reflect light to the telescope's convenient 90° astronomical observing position. In this position the telescope's image is upright, but mirror reversed left to right. While this is normal and poses no problem for astronomy, for terrestrial observing a corrected image is highly desirable which is where this useful accessory comes in. For observing wildlife, a home with a view, or other Earthly applications the Meade #933 45° ETX-60, ETX-70 and ETX-80 Models Image Erecting Prism results in an image both right side up and corrected left to right. The Meade Model 933 ETX-60, ETX-70 and ETX-80 Models Image Erecting Prism also provides a comfortable 45° observing angle which is more convenient for daytime work.