Thermal and aerodynamical analysis of a meridian building

Abstract

AbstractOn a night with low wind speed, the refraction inside a conventional meridian dome can cause a systematic error about 0.”2. In view of the recent improvements of meridian techniques through photoelectric micrometers it is desirable to reduce also this remaining source of error. The present study gives a quantitative theory of the astrometric effect of insulation and ventilation of a meridian building, both for the closed and the open dome, and for daytime as well as for the night. The conclusions are formulated so that they can easily be applied to the design of new buildings and to improvement of existing ones. The design differs from current practice in that e.g. the basement should be well ventilated; the piers must therefore be insulated also in the basement. It is concluded that the slit width is not critical and that a rather narrow slit is therefore altogether preferable, quite opposite to the popular opinion that the roof ought to be completely removed during observation.A building constructed according to these principles, including a slit of 1.4 m width, would have about 5 times smaller thermal effects than the present one in Brorfelde.It would be interesting and simple to extend the methods and results to other astronomical domes in order to diminish seeing effects.