Sizing Guide

If you don't have a set of calipers to measure the diameter of your eyepiece, here's a guide on how you can use a few simple tools to get it done.

You will need:

  1. Thin strip of paper
  2. Pen
  3. Ruler
  4. Calculator

Step  1

Wrap the paper around the circumference of the eyepiece.

Step 2

With the pen, mark where the end of the paper strip overlaps.  (tip: put a little 'x' on the waste side so you know which end of the strip to measure).

Step 3

Measure from the end of the strip to the pen mark.

Step 4

Use the equation for the circumference of a circle (C=pi*d) to calculate the diameter 'd' of the eyepiece.