  Attempts to merge Einsteinian gravity with Newtonian run into inconsistencies
because in Newton's gravity time is absolute and the speed of gravity is
infinite. Such an assumption was in a focus of attention of scientists in 19th
century interested in finding out if the speed of gravity is infinite. By
analogy with electrodynamics, some retarded potentials replacing Newtonian were
utilized. By using one of such potentials Gerber correctly calculated the
perihelion shift for Mercury in 1902. Subsequent attempts at calculation of
bending of light using Gerber-style calculations were not successful. Recently
Gin\'e (Chaos, Solitons and Fractals 42, 1893 (2009)) reobtained both the
perihelion shift and the bending of light using retarded potential. His
equations however are not those obtained by Einstein and his results coincide
with those by Einstein only at the level of leading order terms of infinite
series expansions. The obtained differential equations of motion are of
delay-type. When applied to two-body dynamics, such equations lead to orbital
quantization. In this work the Einsteinian approach is used to reproduce this
quantization. Numerous arguments justifying the superiority of Einsteinian
approach, including uses of the Bertrand spacetimes for description of motion
of stars around galactic centers are provided. The developed formalism is
tested by calculating the number of allowed stable orbits for planets and those
for regular satellites of heavy planets resulting in reasonable agreement with
observational data. The paper also discusses possible quantum mechanical nature
of rings of heavy planets as well as of rotation curves of stars in spiral
galaxies.
