Terry Richardson, Senior Instructor of Astronomy & Physics at the College of Charleston designed a "Make Your Own Safe Solar Viewer" for the upcoming solar eclipse, sunspot cycle 25 and beyond. This set includes our L14810 achromat (52mm diameter by 600mm focal length) and a Barlow lens with a focal length of -27mm. For the achromat: Place the crown (double convex) with its strongest curve against the negative side of the flint. Use a couple pieces of masking tape on the edges to hold them together. The crown side faces the sky. Using an achromat instead of a single element lens you will get to see more of the sunspots and less blue fringe around the sun (chromatic aberration).