On the grounds of a ten-year material of aerological soundings for Poznah (cp = 52" 24'. A = I" 07-5. h, = 85 m) a statistical analysis is made of both temporal and local effects in the pureastronomical refraction. No appreciableeffectsof temporal variationsofhigher layersofthe local atmosphere have been recorded so that the instantaneous local pure refraction can be approximated accurately enough by theaveragc local pure refraction calculated for an instantaneous value of the refractive index n, , at the ground level. A systematicdifference is recorded, howcva, between the standard pure refrao tion calculated for a given value ofn, and the local one. This difference is proved to be rather sharply defined. so it is reasonable to introduce the notion oflocal correction to thestandard pure refraction. For Poznan. thiscorrection is negativeandamountsOi'01 at zo = 60". Oi'I at z, = 77". 1" at zo = 85". and 3" at zo = 87". At z0 = 82" it overestimates the variance of stochastic refraction anomalies (image motion) integrated over time 60 s. The paper answers the long time discussed question whether we should apply the notion of local pure refraction and if yes, in what way.
Auf der Basis von sich uber einen Zeitraum von 10 Jahren erstreckenden aerologischen Messungen fur den Raum Poznah (cp = 52" 24'. A = Ib 0775. ho = 85 m) wurde eine statistische Analyse sowohl zeitlicher als auch lokaler Effekte der astronomischen Refraktion durchgefiihrt. Es wurden keine wahrnehmbaren Effekte zeitlicher Variationen in den hoheren Atmosphirenschichtcn verzeichnet. Damit kann die momcntane lokale Refraktion recht exakt durch die mittlerc lokak Refraktion approximiert wcrden,