The following graphs show intonation measurements
of guitar fretboards.
For each fret, the deviation from the equal
tempered scale is shown in cents. The first data
set is for a Les Paul Special with a fixed
adjustment tailpiece (original). The second
set is for a different Les Paul Special with an
adjustable tailpiece. The third data set is
for a Stratocaster (notice the high E string
could use some intonation adjustment).
These measurements were done using a Precision Strobe Tuner. The deviation for each note was measured by adjusting the calibration vernier knob until the display rotation was stopped. The deviation was read from the calibration setting display. Great care must be taken to stabilize the guitar while each string is measured. Things like a furnace turning on can change the string temperature enough to shift the pitch several cents. The neck must be well supported and the strings should be fretted carefully. Everything affects pitch measureably, furnaces, neck support and fretting technique included. You can change a strings pitch 20 cents by rotating the neck (64 Gibson SG, thin neck) from face up to face down! I expect moon phase has no affect.