Thank you Professor Andy Davidhazy, RIT for teaching schileren method among many other flow visualization techniques. Thank you Dr. Brown of NASA Ames Research center for including me in your experiments.
Decades ago, I was privileged to work (co-op) at the Imaging Technology Branch of NASA Ames Research Center. For most of the experience, I was in awe, fascinated by the brilliant minds, facilities and experiments much like a child would in Disney World.
In one particular photographic assignment at the High-Reynolds laboratory, I was allowed to inquire/propose a moire schileren technique I read and learned from an old text, Schlieren Methods, Douglas William Holder, 1963 (rare but available at RIT library). For knife edge replacements, I created various ronchi rulings with the following result-best case (a) parallel-ronchi-rules-supersonic-flow (b) rotated-ronchi-rules-no-flow (c) rotated-ronchi-rules-supersonic-flow.
Recently, I developed these mobile apps, Machwaves to offer simple photo/video capability and measure mach angle, mach number. As I have no qualifying fluid dynamic experience, I welcome any input or correction on this application. Source code in objective-C and Java is freely available. Information about the app and download sites are available here.