The impact of a wide range of post-Keplerian perturbing accelerations, of whatever physical origin, on different types of observation-related quantities (Keplerian orbital elements, anomalistic, draconitic, and sidereal orbital periods, two-body range and range rate, radial velocity curve and radial velocity semiamplitude of spectroscopic binaries, astrometric angles RA and dec., times of arrival of binary pulsars, characteristic timescales of transiting exoplanets along with their sky-projected spin-orbit angle) is analytically calculated with standard perturbative techniques in a unified and consistent framework. Both instantaneous and averaged orbital shifts are worked out to the first and second order in the perturbing acceleration. Also, mixed effects, due to the simultaneous action of at least two perturbing accelerations, are treated.

The precessions of the Keplerian orbital elements induced by several modified models of gravity are calculated. The latter ones are Yukawa, power-law, logarithmic, dark matter density profiles (exponential and power-law), once per revolution accelerations, constant accelerations, and Lorentz-violating symmetry.