The Danubia 45 Degree Erecting Prism is easy to use as it fits between the telescope and the eyepiece and corrects the viewable image by turning it the correct way up. This means that the viewer can concentrate on where the planets and stars are, rather than thinking in opposites. The Danubia 45 Degree Erecting Prism is angled for added comfort when viewing and is suitable for telescopes with a 1" eyepiece.