I received for test Barlow lens Svbony SV216. The Barlow lens is an optical accessory that allows you to increase the focal length of the telescope several times. It can be used both for visual observations and for astrophotography. The manufacturer claims consistent 2x magnification, fully multi-coated 4-element construction, blackened lens ends, a flat field of view, and a 1.25″ fit with M28.5 x 0.6 filter threads.
SVBONY SV216 1.25″ 2x Barlow lens
However, constant magnification implies another important property – telecentricity, that is, this Barlow lens does not change the slope of the rays coming from the lens. The telecentric Barlow lens cannot be “overclocked” by an additional sleeve, does not increase eyepiece eye relief, introduces less distortion and works better with wide-angle eyepieces.