Calculates the size of a square to fit in an eyepiece field-of-view
  A. Calculate the field-of-view required to fit a square of a given size. This may help you decide if a particular grid or counting reticle will work with your eyepiece.
  B. Calculate the largest square that will fit in a circle (the field-of-view). This may help you decide the largest grid or counting reticle you can use with your eyepiece and still see the corners.
    Calculator - click the "Help" tab above for instructions on use
  A. To calculate the diagonal of a square
    Enter the side of the square    
    Diagonal of the square /    
minimum eyepiece Field Diameter
  B. To calculate the sides of a square to fit in an eyepiece
    Enter Eyepiece Field Diameter    
    Maximum sides of square    
  Calculator A will allow you to enter the sides of a square and give you its diagonal. This is useful to see if the square will fit in the field diameter (the visible area) of an eyepiece.
  Calculator B allows you to enter the field diameter of your eyepiece and then gives you the largest square that will fit all 4 corners. The field diameter is found on the outside of the eyepiece. E.g. 10X/18MM means it is a 10x eyepiece with an 18mm field diameter. Any feature on a reticle larger than 18mm will not be visible.
  Calculator A -- You would like to get our S-14172 reticle which presents a 15x15mm 4 square quadrant (7.5mm ea.) in the field of view. By entering 15mm in calculator A you see you will need a minimum eyepiece field diameter of 21.21mm to see all 4 corners of the quadrant.
  Calculator B --  You have a microscope with a 22mm field diameter and would like to get the largest grid reticle that will fit. By entering 22mm in calculator B you see that is 15.56mm. Therefore the largest grid reticle would be a 15mm square (no's  S-14171, S-14169, S-14173, etc.).
  It is usually more difficult to see the reticle pattern at the very edge of the field diameter. Try and leave a little room between the corner of the square and the edge of the visible field if you want to see the corners clearly.
  It is common to let the corners of a grid or square "run off" the visible field as they may not be needed for your application. And, in fact, you could order a grid pattern larger than the physical size of the reticle, or optical field diameter of your eyepiece, if you simply wanted to fill the field with the grid pattern. For example, an S-14183 20x20mm grid of 10,000 squares on a 20mm physical diameter (or smaller) reticle would cover the entire reticle.