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Orion 1.25" Pentaprism Diagonal - 52055

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SKU: ORI-52055

Orion 1.25" Pentaprism Diagonal

Orion's 1.25" Pentaprism Diagonal features a unique pentagonal-shaped prism, creating a correct image with unparalleled clarity. This makes navigation simple and easy, particularly when using star maps. Most correct-image diagonals cause image degradation from the ridge line where prisms intersect. The Orion Pentaprism Diagonal solves this problem with a sharp, true non-mirror-reversed image. Even at high-power viewing, the diagonal maintains a clear image throughout.

As its name implies, the Pentaprism diagonal consists of a pentagonal-shaped prism, which is made of BK-7 glass that is multi-coated on its two transmitting surfaces and dielectric coated on its two reflective surfaces, for maximum light transmission to the eyepiece. The pentaprism is housed in a black-anodized aluminum body that features a non-marring 1.25" compression ring collar with a large knurled thumbscrew, and a tapered 1.25" barrel that is threaded for use of filters.

The Orion Pentaprism diagonal has an optical path length (backfocus requirement) of 120mm and a generous clear aperture of 29mm. One nice feature of the Pentaprism diagonal is that it causes no vignetting, even when used with long focal length, wide-angle eyepieces. When used in combination with just an eyepiece, the Pentaprism diagonal will render an upside-down image, but not mirror-reversed as you get with a standard star diagonal. That can be advantageous for telescopic viewing with star charts since you need only rotate the star chart to match the view in the eyepiece. A mirror-reversed eyepiece view, on the other hand, requires some mental gymnastics when referring to a star map! While the Pentaprism is the ideal diagonal to use with the Orion Premium Linear BinoViewer, note that it may not provide a correctly oriented view with other binoviewers, which unlike the Premium Linear BinoViewer typically do not incorporate an image erecting lens system.