Importance of small telescopes in the understanding of active hot stars physics

Active hot stars (Be stars) have been observed and studied for more than tw o decades. They exhibit hydrogen emission lines in the visible domain and o ften some emission lines of singly ionized metals. These emissions originat e in a circumstellar envelope produced by a strong radiative stellar wind. Since the discovery of the prototype star of this class (gamma Cas) by Fath er A. Secchi in 1866, the basic physical properties of these objects are st ill poorly known. These stars are also very bright (most of them can be fou nd in the Bright Star Catalogue) which make them good targets for small tel escopes studies. In the following I will focus on some studies that can be done using a 40 cm telescope class. Then I will explain how small telescope s can be combined in an interferometric network in order to reach one milli arcsecond (mas) angular resolution even if each telescope's aperture can be smaller than ten centimeters. With this technics it becomes possible to me asure very small and faint structures on the stellar surface of stars other than our sun.