[stump56]

Agreed. Looks like NASA has made great advances to their schlieren system. Although I prefer the original gray scale images, the colorized ones do make great pictures. The T-38s are going just above Mach 1. Probably around 1.05M (sin(mu)=1/M, if you want to do the calculation).

[DUMBGRUNT]

https://www.nasa.gov/centers/armstrong/feature/NASA_advances_schlieren_imagery_for_supersonic_aircraft.html

BOSCO Chief Engineer Brian Strovers and research engineer Paul Dees calibrate one of three cameras positioned to be able to capture images of supersonic research aircraft. Using a special hydrogen alpha filter, and positioning the cameras to use the sun as a background, NASA researchers are able to observe shockwaves coming off aircraft as they fly faster than the speed of sound, or supersonic. This required pilots to fly through a designated position that was approximately 100 feet in diameter, while flying at supersonic speeds.