In applications in which depth perception is not important, a single telescope, called a monocular, may be employed. Instruments having greater magnifications and light-gathering power are too heavy to hold steady, especially for long periods, but they can be fixed to a tripod or other mount. Handheld binoculars designed for typical uses such as hunting, sports watching, nature study, or amateur astronomy range from about 6×30 to 10×50. For a given magnification, larger objectives produce a brighter image in dim light but also create a more massive pair of binoculars. This latter figure is a measure of the light-gathering power of the instrument. The first number indicates the magnification (e.g., 7×, meaning “7 times”) and the second the diameter of the objective in millimetres (1 inch is about 25 millimetres). The primary optical characteristics of a pair of binoculars are commonly described by two numbers, the first of which is followed by a multiplication sign-for instance, 7×50. The arrangement of these prisms and the other optical components is shown in the illustration. When the prisms used are of the Porro type ( see optics: Reflecting prisms), they also provide better depth perception at greater distances by allowing the two objectives to be set farther apart than the eyepieces. They prescribe a folded path for the light rays, allowing a shorter overall length for the instrument. The prisms reinvert, or erect, the inverted image supplied by the objective of each telescope. In most binoculars, each telescope is provided with two reflecting prisms. SpaceNext50 Britannica presents SpaceNext50, From the race to the Moon to space stewardship, we explore a wide range of subjects that feed our curiosity about space!.Learn about the major environmental problems facing our planet and what can be done about them! Saving Earth Britannica Presents Earth’s To-Do List for the 21st Century.100 Women Britannica celebrates the centennial of the Nineteenth Amendment, highlighting suffragists and history-making politicians.COVID-19 Portal While this global health crisis continues to evolve, it can be useful to look to past pandemics to better understand how to respond today.Student Portal Britannica is the ultimate student resource for key school subjects like history, government, literature, and more.This Time in History In these videos, find out what happened this month (or any month!) in history.#WTFact Videos In #WTFact Britannica shares some of the most bizarre facts we can find. Demystified Videos In Demystified, Britannica has all the answers to your burning questions.Britannica Classics Check out these retro videos from Encyclopedia Britannica’s archives.Britannica Explains In these videos, Britannica explains a variety of topics and answers frequently asked questions.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |