  V505 Per is a detached eclipsing binary containing two F5 V stars in a 4.22-d
circular orbit. We use a light curve from the TESS satellite and published
radial velocity measurements to establish the properties of the system to high
precision. The masses of the stars are 1.275 +/- 0.004 Msun and 1.258 +/- 0.003
Msun, and their radii are 1.294 +/- 0.002 Rsun and 1.264 +/- 0.002 Rsun. Adding
published effective temperature estimates, we precisely measure the
luminosities and absolute bolometric magnitudes of the stars, and the distance
to the system. The distance is slightly shorter than that obtained from the
Gaia EDR3 parallax, a discrepancy most easily explained by uncertainty in the
2MASS K-band apparent magnitude. We reanalyse existing light and radial
velocity curves from three previous studies of this system and conclude that,
in this case, formal errors are reliable for the spectroscopic orbits but not
light curves, that errorbars from a residual-permutation algorithm are suitable
for light curves but not spectroscopic orbits, and that published results are
not always reproducible. The precisions in the measured properties of V505 Per
are high and among the best ever obtained for a detached eclipsing binary
system.
