This diagram shows the path of two light rays refracted by the lenses of a Galilean telescope.

If you haven't already done so, first download the free trial version of RFFlow. It will allow you to open any chart and make modifications.

Once RFFlow is installed, you can open the above chart in RFFlow by clicking on Optics_Illustration.flo. From there you can zoom in, edit, and print this sample chart. It is often easier to modify an existing chart than to draw it from scratch.

To access different styles of lines, run RFFlow and click on the More Shapes button. Scroll to the Lines folder and click the plus sign to open it. Click one of the stencils and then click the Add Stencil button.