Characterization of flow in the HET enclosure following ventilation and application of low-emissive coatings

John M. Good

doi:10.1117/12.552501

28 September 2004 Characterization of flow in the HET enclosure following ventilation and application of low-emissive coatings

John M. Good

Author Affiliations +

Proceedings Volume 5489, Ground-based Telescopes; (2004) https://doi.org/10.1117/12.552501
Event: SPIE Astronomical Telescopes + Instrumentation, 2004, Glasgow, United Kingdom

Abstract

In 2002 the method of thermal control within the HET enclosure was dramatically changed by the installation of 300 square meters of ventilated area to the stationary walls below the rotating dome. During the month of July 2003 a nightly study of the airflow was undertaken at the HET. While dome seeing has shown substantial improvement, this study revealed a number of counter intuitive flow modes which indicate that additional seeing improvements can be achieved by selective ventilation of the HET dome above the ring-wall. Additional study of dome seeing revealed substantial sub-cooling of the dome skin. Measurements of the skin temperature of the un-insulated dome revealed night-time cooling of local ambient air by as much as 3.6° C. An investigation of coating alternatives resulted in the application of aluminum foil tape, which reduced the temperature drop to 0.3° C. Presently, the performance of the HET (as low as EE50=0.8 arc-seconds) is not thought to be limited by dome seeing.

Citation Download Citation

John M. Good "Characterization of flow in the HET enclosure following ventilation and application of low-emissive coatings", Proc. SPIE 5489, Ground-based Telescopes, (28 September 2004); https://doi.org/10.1117/12.552501

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