This document describes how to calibrate the divisions on an eyepiece graticule by superimposing it over a stage micrometer with a known scale. The number of graticule divisions that correspond to a set number of micrometer divisions is counted to determine the width each graticule division represents. This allows the actual size of objects viewed through the eyepiece to then be measured.

1. Calibration of Eyepiece Graticules

2. Eye Piece Graticules
Fitted in the
eyepiece
100 divisions
Arbitrary units
Needs Calibration

3. Stage Micrometer
10mm
100 divisions
Each is 0.1mm

4. To Calibrate
Superimpose the two scales
Match up two points
Count the number of epg divisions = x
Count the number of micrometer divisions = y

6. One micrometer division is 0.1mm
Total width = y x 0.1mm
If there are x epg divisions
So x epg divisions = y x 0.1mm
then ONE epg division = (y x 0.1) mm
X
You may need to convert to
micrometers

7. If you have an object on this power you can now
find the Actual Size of the image
Count the number of epg divisions
Multiply by the calibrated width of one division

8. Magnifcation =
Size of drawing (mm)
Actual size of object (mm)