The Thermal Environment of the Fiber Glass Dome for the New Solar Telescope at Big Bear Solar Observatory

TL;DR

This study investigates the thermal environment inside a fiberglass dome for a solar telescope, measuring temperature gradients and evaluating active venting to optimize thermal regulation and reduce seeing effects.

Contribution

It provides detailed temperature measurements and analysis of a fiberglass dome with active vents, integrating findings into the thermal control system for improved telescope performance.

Findings

Confirmed a 5°C thermal gradient inside the dome.

Demonstrated effectiveness of vent configurations in controlling temperature.

Integrated thermal data into the telescope's control systems.

Abstract

The New Solar Telescope (NST) is a 1.6-meter off-axis Gregory-type telescope with an equatorial mount and an open optical support structure. To mitigate the temperature fluctuations along the exposed optical path, the effects of local/dome-related seeing have to be minimized. To accomplish this, NST will be housed in a 5/8-sphere fiberglass dome that is outfitted with 14 active vents evenly spaced around its perimeter. The 14 vents house louvers that open and close independently of one another to regulate and direct the passage of air through the dome. In January 2006, 16 thermal probes were installed throughout the dome and the temperature distribution was measured. The measurements confirmed the existence of a strong thermal gradient on the order of 5 degree Celsius inside the dome. In December 2006, a second set of temperature measurements were made using different louver configurations. In this study, we present the results of these measurements along with their integration into the thermal control system (ThCS) and the overall telescope control system (TCS).