As part of a larger project for measuring various aspects of foldable domes in the context of EST and with support of the
Dutch Technology Foundation STW, we have collected over a year of continuous temperature and humidity measurements,
both inside and outside the domes of the Dutch Open Telescope (DOT) on La Palma5 and the GREGOR telescope on
Tenerife.6 In addition, we have measured the wind field around each dome.
Although the structure of both domes is similar, the DOT dome has a single layer of cloth, and is situated on top of an
open tower. In contrast, the GREGOR dome has a double layer of cloth, and is situated on top of a tower-shaped building.
These differences result in large differences in temperature and humidity insulation when the dome is closed. We will
present the changes in temperature and humidity one can expect for each dome within one day, and the statistics for the
variations throughout a year.
In addition, we will show that the main advantage of a foldable dome is the near instantaneous equilibration of the air
inside the volume originally enclosed by the dome and that of the environment outside the dome. This property allows
one to operate a telescope without needing expensive air conditioning and dome skin temperature control in order to limit
dome and shell seeing effects.
The measurements give also information about the weather fluctuations at the sites of the domes. It was observed that
on small time scales the temperature fluctuations are significantly greater during the day than during the night.