Practical Parasitology

The Vernier Scale and Vernier Coordinates


Overview

The recording of vernier coordinates is necessary to relocate a particular organism or artifact on a slide. This may be necessary to point out an organism for referral or just to share your finding with a colleague. The coordinates are recorded along an X axis and a Y axis (X,Y). The X axis running from left to right and the Y axis running from top to bottom.

Method

If relocation of the specimen is limited to one particular microscope, or at the very most a microscope by the same manufacturer it is a rather simple matter of recording only one set of (X,Y) coordinates. Refer to the accompanying illustrations. In most instances however, relocation is required to confirm the presence of an organism by a referral laboratory. In this case a series coordinates are required.
Record the following.

  1. Place the slide in the slide clip and record whether the label is on the left or the right.
  2. Record the coordinates of the upper right corner of the coverslip or the lower left corner (X,Y). Make a note as to which corner you selected. You may also make a mark on the slide as a reference point. Don't forget to make a note of it's coordinates!
  3. Record the coordinates of the object (X,Y) centered in the field.
  4. Draw a diagram of the field recording any landmarks that may be useful in relocating the specimen.

Vernier Coordinates

The vernier coordinates are obtained from the scales running along the top and side of the microscope stage. The X coordinate is obtained using the scale at the top of the stage running from right to left and the Y coordinate is obtained using the scale running from top to bottom along the side of the stage. The following illustrations show the X and Y vernier scales with examples.

X axis vernier scale reading 37.4 Y axis vernier scale reading 102.5

With the above information you can easily calculate how many millimeters from the reference point (that you selected and noted with its' coordinates) you are no matter which microscope you must relocate the object with.