  With the basic cosmological relations that agree with the recent
observations, simple expressions are suggested concerning the value of
cosmological constant($\Lambda$). A large contribution of quantum vacuum to the
energy momentum tensor does not agree with the observed cosmos. However,one
requires the presence of positive $\Lambda$ to make the various observations
consistent. After a review of the effect of cosmological constant on the
geodetic motions in the Schwarzschild de Sitter spacetime, some approaches to
its solutions are briefly discussed. Also suggested is the very weak limit on
$\Lambda$ from the planetary perturbations.
