Celestron 45-Degree Erect Diagonal (1.25")

Celestron's erect image diagonals are Amici prism designs, allowing you to look into the telescope at a 45° angle at images which are upright and laterally correct.  This is extremely comfortable for terrestrial viewing or when sharing the viewing experience between those of varying heights, and comes at the expense of a loss in brightness versus a 90° diagonal-which would show images upright but laterally reversed.