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Accessories: 45^o Prism 1-1/4" Diagonal

This 1-1/4" 45 degree diagonal allows correct image viewing with telescopes. The accessory end of the diagonal has a brass compression ring so that eyepieces will not be marred when secured to the diagonal.

A new design feature is the safety ramp incorporated in the diagonal barrel. Instead of the safety undercut often used on eyepieces and some diagonals, the barrel of the prism diagonal has an undercut ramp that allows the diagonal to be securely and safely attached with either a brass compression ring or with thumbscrews. There is no sharply angled surface to catch a compression ring. The ramp shape prevents the diagonal from sliding out of the telescope if the compression ring or setscrew loosens during use.

Typically, prism diagonals are not suggested for astronomical use because of the loss of light through the prism. However, this prism diagonal has all surfaces fully broadband coated for maximum light transfer. Also, when viewing the planets or the moon, any light loss compared to a mirror diagonal is of less concern. The correct image view of the moon and planets makes it easier to correlate the view through the telescope to the images on printed charts and maps.

With a spotting telescope, a 45 degree diagonal is essential. For terrestial viewing, the 45 degree diagonal provides correct image views with the eyepiece at a comfortable angle.

The barrel of the prism diagonal is threaded for 1-1/4" filters. The prism diagonal has a clear aperture of 25.5mm, which is slighly less than the maximum 27mm clear aperture of 1-1/4" accessories. The prism diagonal adds approximately 1-1/16" (28mm) to the optical path compared to a typical 1-1/4" mirror diagonal. This means that the focus tube will be racked in further than if a mirror diagonal were used. The 1-1/4" prism diagonal weighs 5.5 ounces.

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