Figure 2.

How to make the bottle base and bottle top (a) and (b)? The bottle base is marked and is cut along the marked line (denoted by red dotted line). (c) The condensing lens is the fit into the cut area of the bottle. (d) Measure and cut the appropriate size of black sandpaper/chart paper. (e) Insert the sandpaper/chart paper into the bottle. (f) The bottle with the sandpaper/chart paper fit inside. (g) and (h) The bottle top is stuck to the smartphone cover by fevikwik (superglue). (i) The smartphone is attached to the bottle top with a universal smartphone adapter