11. Geometrical optics does not account for certain optical effects such as diffraction and imaging, including optical aberrations . 12. These optical aberrations are not normally seen in daylight because they require a dark background to be seen. 13. In 1950 he created an aerial 90?viewing-angle lens Aviogon, which was free from optical aberrations . 14. Piston and tilt are not actually true optical aberrations , as they do not represent or model curvature in the wavefront. 15. While in principle a lens elements is required to correct ( as much as possible ) the many optical aberrations that arise. 16. Additionally, the light is reflected off of a deformable mirror before and after exposure to the eye to diffuse optical aberrations . 17. However, precision optical surfaces normally need the reflective material on the front surface of the glass to avoid introducing optical aberrations . 18. In contrast to the microscope, the objective lens of the telescope was designed with a large focal length to avoid optical aberrations . 19. These optical aberrations diminish the quality of the image formed on the retina, sometimes necessitating the wearing of spectacles or contact lenses. 20. It is more difficult to reduce optical aberrations in telescopes with low f-ratio than in telescopes with larger f-ratio.
