Estimating local seeing at the DCT facility

A thermal model of the Discovery Channel Telescope (DCT) was used to estimate the contribution of major sources of local seeing; shell seeing, dome seeing and mirror seeing. The model simulates a dynamic equilibrium over several day/night cycles taking into account the morphology of the facility, diurnal insolation and radiation to the night sky, local air temperature and humidity swings, wind and air flow through the facility, and infiltration from warm spaces within the facility. The model confirmed that the well ventilated design of the DCT facility will virtually eliminate dome seeing, but that shell seeing and mirror seeing could be major contributors to local seeing. These can be mitigated by the choice of an appropriate exterior coating, and by cooling the primary mirror.