| This 2 2x Clamp Ring Big Barlow can be used with any telescope using a 2" focuser. As it is only 4.5" long, it can also be used in most 2 star diagonals for 2x magnification. It can also be placed into a 2 focuser in front of a 2 star diagonal to give higher magnification than the nominal 2x. Some refractors might not have enough focuser travel to allow this directly, however. For example, all 2 focuser TeleVue refractors require adding a 3.5 extension tube #1343C between the scope and Barlow to allow the Barlow and eyepiece to reach focus. In this configuration, the magnification is about 3.3x instead of the expected 2x. This Big Barlow uses non-marring brass clamp rings to hold 2 eyepieces and the supplied low profile 1.25 eyepiece adapter in place. The captive thumbscrew on the Barlow that tightens its clamp ring cant be lost in the field. The Barlow is parfocal with TeleVue eyepieces. The Barlow is antireflection threaded, with blackened lens edges for high contrast. It is fully multicoated and threaded for 48mm filters. The Barlow is corrected for use with telescopes having focal ratios down to f/4. Using the Big Barlow with 27mm and 35mm Panoptic eyepieces requires an optional #PAN00 interface lens to maintain eye relief, avoid vignetting, and improve the field edge performance. The #PAN00 interface is helpful, but not essential, with the 22mm Panoptic, but is not needed with the 15mm or 19mm Panoptics. |
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