B20/B21 Specifications

PL1 B1/B1C B20 B21 Image Erect Erect Erect Erect Magnification 42x 32x 32x or 40x (opt.) 30x Resolving Power 2” of arc 3" n/a n/a Field of View 1° 10' (2.0 ft. @ 100 ft.) 1° 20’ (2.3 ft. @ 100 ft.) 1° 20’ (2.3 ft. @ 100 ft.) 1° 20’ (2.3 ft. @ 100 ft.) Minimum Focus 6.6 ft. (2m) 7.5 ft. (2.3m) 1 ft. (0.3m) 1 ft. (0.3m) Stadia Ratio 1:100 0.3:100 or 1:100 1:100 1:100 Compensator — PL1 (split-image tubular vial); all others (wire-hung; magnetically damped) Setting Accuracy n/a 0.3" 0.3" 0.5" Range n/a ±10' ± 15' ± 15' Leveling Accuracy (all models)—in 1.0 km (1 mile) of double-run leveling Standard Deviation ± 0.2mm / 001 ft. ± 0.8mm / .003 ft. ± 1.0mm / .004 ft. ± 1.5mm / .006 ft. w/ micrometer .001 in (0.1m) ± 0.5mm / .002 ft. ± 0.8mm / .003 ft. ± 1.2mm / .005 ft. Level Vial (all models) — circular Sensitivity 3.5' / 2mm 10' / 2mm 10' / 2mm 10' / 2mm