I use the same lens as Chris, and it can be difficult. I don't use a fresnel. Be sure you are blocking out all extraneous light with the darkcloth. Stay under the darkcloth for a minute or so, so that your eyes can adjust. To check the corners and edges, realize that the arial image is being projected at quite a wide angle, so you can't see it if your eyes are parallel to the groundglass. You might need to tilt the loupe to catch the arial image.