Whether you are a telescope or binoculars, application of ace rookie, are a little use should not be neglected, that is before you decide to buy your porro telescope, must understand the basic design of the telescope. The so-called mutant ever victorious, it can bring you the correct choice. Good luck!

There are two basic and conspicuously different types of designs. All binoculars either use "porro prisms" or "roof prisms". The ones using porro prisms are the traditional design where the eye pieces are off-center to the barrels, whereas the ones using roof prisms the eye pieces are in line with the objective lenses and have a sleek design. Porro prism binoculars are, generally speaking, less expensive and have greater three-dimensional viewing effect, whereas roof prism binoculars are more compact and lighter, but are usually more expensive. Making a roof prism design binocular weatherproof is also easier and more successful.

Central focusing knob/wheel: The knob between the two optical barrels by means of which you change the focus when looking at an object. Some binoculars have a toggle switch focus in stead of a wheel/knob.

Diopter: This is a focus control knob (usually at the right eyepiece) that lets you focus one side of the binoculars separately from the other, in order to set the binoculars to accommodate differences in the focusing of your two eyes. Some binoculars have diopters for every eyepiece.

Source:   Big Porro Binoculars ,  Monocular Telescope

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