Published online by Cambridge University Press: 04 August 2017
Some aspects of the design for a Glass Meridian Circle with 24 cm aperture are presented and discussed. Tangential ventilation will be used to minimize tube refraction. The air for the ventilation will be filtered and it will provide a clean atmosphere around all optical and critical mechanical components, thus improving reliability. The base frame and piers are particularly stable thanks to a sharp separation between parts with short and long thermal time constants. The instrument is compact and portable and it requires only a small dome.