Do Astronomical Telescopes Yield Inverted Images?
Yes. To avoid light dispersion and an alteration of the optical quality, most astronomical telescopes are reverting the picture of the object observed. Refractors and SCTs are yielding an upside-down image as Newtonians and Dobsonians are rotating the image depending on the eyepiece’s angle relative to the vertical. Should the user want to use its astronomical telescope for terrestrial purposes, he will have, if possible, to use an optical device, called an “erect-image” or a “correct-image prism diagonal”, which will gives back the picture its normal look. Unfortunately such erecting prisms do not work with Newtonians (hence with Dobsonians). Erecting prisms usually come at a 45° angle. Binoculars are yielding normal images and may be used for terrestrial or astronomical purposes.
