Abstract. Object images obtained by mean of ground based instrument are degraded by the earth atmosphere. Indeed, the wave-front at the entrance of the instrument pupil, present phase and amplitude random fluctuations depending of the time, the position and the line of sight. The recorded images are consequently filtered leading to bad measurements of the studied object parameters. To qualify the atmospheric degradations, several parameters are commonly defined. For solar diameter measurements performed with an astrolabe, errors due to the atmospheric turbulence are directly related to these parameters. After, a brief recall of the basic properties of the atmospheric turbulence, a method allowing to generate realistic random wave-fronts will be presented. They will be used to study errors on diameter measurements performed with a solar astrolabe. The obtained results will clearly show the necessity to have a seeing monitor observing together with the solar experiment. A method allowing to obtain the observation conditions for solar observation will then be given.