You must click on this link to begin: Start Me. The object (the arrow), its image and the principal rays can be moved by clicking & draging the top of the arrow shaped object in the animation.

• With respect to starting configuration find the focal length. Now move the object and see if you can find a position in which the image and object heights are the same.
• Restart the simulation and now add a second, convex lens, by clicking on the Add 2nd lens link. This 2nd lens will render a final image which is real. The image with a "1" by it is that of just the convex lens while the image with a "2" next to it is that of the pair. Move the object and alter its height, if necessary, so that the first image has the relationship q₁ = 2 p₂.
  This qualitatively resembles your actual set-up (in this case |f₂| = 3 |f₁|).
• Now repeat the last step with |f₂| = |f₁| by clicking on: Another 2nd lens. Finally reset to the "Another 2nd lens" and then click on the convex lens and drag it past the diverging lens.