Rawson sights are Australian and are one of the many popular tangent sights used for target shooting in Australia over the years. While I do not own a Rawson (Mine are (OZ) Mues or Central) ... the vernier principle is generally the same for all these sights.
The elevation and windage divide on the vernier principle of 100th of an inch each. Your 100th equals 1 inch on the target for every 100 yards of range. Put it another way, adjustment usually is one click per half or full minute of angle, for half or one inch of adjustment on target at 100 yards.
What I don't know is whether you sight is set for 1/4 or 1/2 click adjustments. That will make a difference ...
Last edited by Tikirocker; February 13, 2013 at 12:14 AM.