Determining the intensity of a point-like source, observed with an extended source as the background

The paper deals with the gravitational lensing problem formulated as determining the intensity of a point-like source, observed with an extended source as the background. The mathematically accurate statement of the problem was proposed. The Bayessian statistical approach was recommended as the most proper one for solving the problem. The expressions obtained are useful for the complete algorithm of a point-like source intensity determination.