Objective diameter: 81 mm
Focal length: 480 mm
IPD: 57 – (>) 80 mm
Focal ratio: f/5.9
Weight (w/o eyepieces, with eyepiece cover and objective caps): ca. 4‘100 g
Made in: Japan
Just slightly larger than its sibling with 70mm lenses, the Vixen 81 is an achromat – whereas the Vixen 70 features ED glass – and is significantly less costly than the latter. In fact, it is currently perhaps one of the cheapest quality BTs in the 80mm range of instruments; it does show more color fringes than the 70 ED model, but the chromatic aberration is overall still very acceptable, and BINOCULARS TODAY actually prefers the image in the 81 which is clearly brighter than in the 70 ED. Now a bit dated, Vixen’s 81 mm model does still provide stunning views of objects on the night sky when it is used with good eyepieces, with best results at magnifications between 26x and 48x (eyepieces 18mm-10mm).
see also remarks under separate post “Vixen BT-ED70S-A”, https://binocular.ch/vixen-bt-ed70s-a/