Televue 2x Big Barlow 2 inch

Properly designed Barlows do wonderful things. First, they amplify power while retaining the eyepiece's eye-relief. Second, they slow the telescope's f/#, which improves eyepiece sharpness. Third, the designer can introduce compensations for eyepiece aberrations.Tele Vue's 2" 2x BIG Barlow, 1 1/4" 2x and 3x Barlows were envisioned as magnification windows. Multi-coated high index glasses assure optimum aberration correction, exceptional contrast and virtually no light loss. Tele Vue Barlows achieve their design goals even when tested by the fastest scopes. They even improve our competitor's eyepieces and telescopes!For eyeglass wearers, the Big Barlow is perfect for doubling the power while retaining the eye-relief of 2" Tele Vue eyepieces such as the 55mm Plossl, 35mm and 27mm Panoptics (requires use of Panoptics Barlow Interface) and 20mm Nagler Type 2.Our design approach includes mechanical conveniences. The Barlows are parfocal with our eyepieces and the BIG Barlow includes a parfocal 2" - 1 1/4" adapter. The BIG Barlow is threaded for 48mm filters and has a captive lock-screw. Both 1 1/4" Barlows are threaded for 1 1/4" filters.Barlows do more than just increase magnification; they also retain eye relief (or in the case of long focal length eyepieces, actually INCREASE eye relief). A high quality Barlow must be properly designed and manufactured in order to avoid compromising a telescope's color correction and spherical aberration corr