See Appendix B of this (or similar) document.
https://oehler-research.com/wp-content/uploads/2017/11/M36-Instructions.pdf
TLDR: If your optical chrono is properly aligned with the projectile trajectory, it's results are probably correct at it's location, except for grossly/obviously erroneous results.
Verification Process:
1) Use electronics voodoo tool to verify electronic clock is running at 66 Mhz, and
2) confirm (measure) that the distance between projectile triggers of the clock are the same as what the algorithms assume.
"Such counting and computations [as used in the Oehler chronograph] are commonplace and are normally subject to gross failures but not small errors." Clock may have 0.25% (1/4-%) error limited by the electronics.
The chrono should be aligned with the projectile path. 8* off can cause 1% error in trajectory distance and measured speed.
"The digital counting and computation is assumed to be correct. No calibration is required or suggested. If verification is required, we suggest use of the Oehler Model 76 firing simulator as a source of trigger pulses at known time intervals.
"The spacing between projectile sensors must be accurately determined during the operation and use of the system. Appropriate calibration and use of measurement devices is assumed."
