JOHN BROWNING'S WATER IMMERSION OBJECTIVE
Circa 1880
Shown below is a Browning 1/8" water immersion objective with correction collar. The 63 Strand address dates it to the period between 1872 and 1900. The correction collar is calibrated from wet
to covered
. The Angular aperture of 135o corresponds to a numerical aperture of 0.94 in water but 0.71 in air.
