History of the telescope
The earliest known telescope appeared in 1608 in the Netherlands when an eyeglass maker named Hans Lippershey tried to obtain a patent on one. Although Lippershey did not receive his patent, news of the new invention soon spread across Europe. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo improved on this design the following year and applied it to astronomy. In 1611, Johannes Kepler described how a far more useful telescope could be made with a convex objective lens and a convex eyepiece lens and by 1655 astronomers such as Christiaan Huygens were building powerful but unwieldy Keplerian telescopes with compound eyepieces.
Experimental psychology
The first stereoscope was invented by Wheatstone in 1838. It presents two slightly different images, one to each eye, at the same time. Typically the images are photographs of the same object taken from camera positions that mimic the position and separation of the eyes in the head. When one looks through the steroscope the photos fuse into a single image that conveys a powerful sense of depth and solidity.