  Complete sets of reference magnitudes in all 7 Johnson-Cousins bands (U, B,
V, R, I, Rc and Ic) and the 5 principal Sloan bands (u', g', r', i', and z')
are presented for the 8 planets. These data are accompanied by illumination
phase functions and other formulas which characterize the instantaneous
brightness of the planets. The main source of Johnson-Cousins magnitudes is a
series of individualized photometric studies reported in recent years. Gaps in
that dataset were filled with magnitudes synthesized in this study from
published spectrophotometry. The planetary Sloan magnitudes, which are
established here for the first time, are an average of newly recorded Sloan
filter photometry, synthetic magnitudes and values transformed from the
Johnson-Cousins system. Geometric albedos derived from these two sets of
magnitudes are consistent within each photometric system and between the
systems for all planets and in all bands. This consistency validates the
albedos themselves as well as the magnitudes from which they were derived. In
addition, a quantity termed the delta stellar magnitude is introduced to
indicate the difference between the magnitude of a planet and that of its
parent star. A table of these delta values for exo-planets possessing a range
of physical characteristics is presented. The delta magnitudes are for phase
angle 90 degrees where a planet is near the greatest apparent separation from
its star. This quantity may be useful in exo-planet detection and observation
strategies when an estimate of the signal-to-noise ratio is needed. Likewise,
the phase curves presented in this paper can be used for characterizing
exo-planets. Finally, magnitudes for the proposed Planet Nine are estimated,
and we note that P9 may be especially faint at red and near-IR wavelengths.
