Sky Mentor 45º Erecting Diagonal - 1.25" An image erect diagonal is really nice to have if you want to use your telescope terrestrially as a spotting scope! Out of the box, most astronomical telescopes produce a mirror image. Astronomers do not bother to correct this image when looking at or photographing the sky, as doing so adds another bounce of light that lowers image brightness a bit. However, image brightness is normally not a concern during the day, and it is nice to have a right-side up, left to right correct image when using your scope to look at objects here on earth. To correct the image, simply insert this erect image diagonal into the 1.25" focuser (or focuser adapter) of your telescope and then use eyepieces as normal. Please note that this diagonal does not erect the image correctly for Newtonian telescopes, but it works well for refractors and catadioptric scopes like Schmidt-Cassegrain or Maksutov models.
