BS.1 Specifications
| Magnification | 8x | 10x |
| Obj. lens diameter | 42mm | 42mm |
| Exit pupil | 5.25mm | 4.2mm |
| Field of View (FOV) | 8.0° | 6.6° |
| Apparent FOV (FOV x Power) | 64° | 66° |
| Field of view (ft/1000 yds) | 420 | 362 |
| Brightness | 27.6 | 17.6 |
| Light transmission (%) | 93.95% | 94.50% |
| Twilight factor | 18.3 | 20.5 |
| Multi Position Eyecups Y/N | Yes | Yes |
| Eye relief | 18.1mm | 17.8mm |
| Near focus | 4.9ft | 4.9ft |
| Eye width adjustment | 56~74mm |
56~74mm |
| Dimension WxHxD | 5.2x5.7x2.2 | 5.2x5.7x2.2 |
| Weight | 26.808 oz | 26.808 oz |
| Lens constr. obj. | 3 groups 4 elements (ED) | 3 groups 4 elements (ED) |
| Lens constr. ocular | 4 groups 5 elements | 4 groups 6 elements |
| Prisms type | Wide Angle Schmidt-Pechan |
Wide Angle Schmidt-Pechan |
| Prism reflective coating type | Dielectric Coating | Dielectric Coating |
| ED glass | Yes | Yes |
| Lens coating | Scratch and Oil Resistant | Scratch and Oil Resistant |
| Diopter correction (dpt) | +/-3 | +/-5 |
| Pressure tested to what pressure | 1m for 30 min. (IPX7) | 1m for 30 min. (IPX7) |
| Storage temperature | -40°~158°F | -40°~158°F |
| Functional temperature | -13°~140°F | -13°~140°F |
| Frame material | Magnesium | Magnesium |
| Internal gas purged | Nitrogen | Nitrogen |
| Tripod Adaptable Y/N | Yes | Yes |
| Origin | Japanese components assembled in the US | Japanese components assembled in the US |