After eyepieces, zenith prisms are the most important accessories for refractors and Schmidt-Cassegrain or Maksutov reflecting telescopes. They are needed for a more comfortable viewing during zenith observations or for image inversion. On Newtonian reflectors, these accessories cannot be used for optical reasons - and do not need to be, since the optical path in the Newtonian telescope makes this unnecessary. This zenith prism provides an upright, side-swapped image. All Celestron zenith prisms have a high quality coating.