A ALSTAR Alstar 1.25" 90-Degree Erecting Prism Optical Prism Inside Rather Than a Mirror which Makes Your Image Clear and Sharp

1. 25" 90-degree diagonal features an image erecting prism that allows you to look into a telescope at a 90 degree angle. It produces an image that is oriented properly, which means that the image is upright and correct from left to right (i. e. , a correct, non-inverted, non-reversed image). This is a great diagonal for daytime terrestrial use with small telescopes or spotting scopes. It can also be used for astronomy applications, especially when you would like to match the orientation of the star field with "correct" star maps and charts. The prism housing is made of precision molded ABS plastic and the two end barrels are precision machined from aluminum. The 1. 25" nosepiece is threaded to accept standard 1. 25" astronomy filters. Please Note: This diagonal can only be used with refractor telescopes and some catadioptric telescopes like Schmidt-Cassegrain, Maksutov-Cassegrain, etc. It not meant for use with Newtonian / Dobsonian reflector telescopes or other variants of Newtonian telescopes.