Celestron’s Erect Image Diagonals are an Amici prism design. This design allows you to look into the telescope at a 45° angle, at images that are oriented properly, meaning the image is upright and correct from left to right. Use of Celestron’s .96" to 1-1/4" 45° Erect Image Diagonal on a telescope equipped with .96" eyepieces means greater versatility. This diagonal will allow you to use 1-1/4" eyepieces, to obtain a larger field of view and better eye relief. A 90° 1-1/4" Erect Image Diagonal is available for those who prefer that angle. A Star Diagonal lets you view objects that are at a 90° angle from the direction the telescope is pointing, thereby allowing comfortable viewing when the telescope is pointed at, or near, the zenith (i.e. directly overhead). The resulting image is right side up, but will be reversed from left to right.