I have used this prism diagonal for several years in both deep sky and planetary/double star applications and would concur with the assessment of William Paolini, in his review of twelve mirror, dielectric and prism diagonals (Cloudy Nights, 2014): the best include Baader's 1.25 inch and 2.00 inch prisms, and VERNONscope's enhanced-silver mirrors. The prisms may have a slight edge for planetary, and the mirror, for deep sky; the prisms may have very (very!) slight chromatic aberration with focal ratios of less than f/7. This T2 Baader prism, additionally has a helical focus built-in, for fine adjustment, and is surprisingly lower in cost than the other premium products. My one annoyance with it: the three set screws used to secure the eyepiece. One always seems to be colliding with my nose! I solve this by simply removing one or two of the set screws. If you are not going to spend more than $500 for a diagonal, this one should be a serious consideration.