Tele Vue New 5x Powermate Barlow lens 1.25" - T Ring Adaptable.

Tele Vue Barlows: "An Optically Perfect Window " 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. The 2.5X Powermate Barlow is a 4-element parfocal, compact amplifying lens system. POWERMATE consists of a negative achromatic doublet plus a positive "pupil-correcting" doublet. While it looks and functions like a Barlow, your eyepiece will operate with pupil locations where the designer intended, avoiding mismatch problems. POEWRMATE optimally mates its power to your eyepieces. No additional "interface lens" is needed, since POWERMATES have it built-in. In addition to full multi-coating, POWERMATE includes other Tele Vue special touches such as a safety undercut on the chrome barrell, and captive lock screws that can't fall out. Tele Vue's 100% QC program at f/4 insures that POWERMATE will add dramatic power (and NOTHING ELSE) to your favorite eyepieces. If, for example, you own a 22mm Panoptic, you'll have the power of an 8.8mm focal length eyepiece with the 2.5x POWERMATE. The POWERMATES are constructed to be parfocal with Tele Vue's 1-1/4" 90 degree diagonal (often used in Ranger telescopes) adding convenience not previously available with any Barlow. The 2.5X POWERMATE has no filter threads Dobsonian/Ne