Achromatic Refractor Telescopes
The achromatic refractor telescope has two glass or lens elements called crown and flint, that refracts or bends the light converging its rays to project an image at a focal plane, enlarging or magnifying any object’s size visually like a magnifying glass for reading or crafting will do. Refractor telescopes are the best known historically since Galileo Galilei used the single element refractor for his study of the moon, the planet Jupiter, and solar observations. They show less chromatic aberration with focal ratios between f/12 to f/15. This aberration consists of blue/purple light wavelength not converging at the same focal plane as red and green light wavelengths resulting in blue hues out of focus noticeable around bright objects like the Moon, Jupiter, Venus and bright stars.