Tele Vue 3x Barlow 1 1/4"Description TeleVue Barlows reduce aberrations to below the airy disc in an f 4 system and lay to rest the popular myth of the "degrading Barlow." Properly designed Barlows do wonderful things: They amplify power, slow the telescope's f # (improving eyepiece sharpness), and give designers the opportunity to compensate for eyepiece aberrations. Tele Vue Barlows use multi coated high index glasses for optimum aberration correction, exceptional contrast