The Advanced Technology Solar Telescope (ATST) is a large domed solar telescope facility that is planned to be built by the National Solar Observatory atop the Haleakala volcano on the Pacific island of Maui, Hawaii, USA. The site was selected for its clear daytime atmospheric seeing conditions, which will enable study of the solar corona. The ATST enclosure will house a 4-meter diameter solar telescope capable of observing objects on the Sun that are 30 km across.

The ATST aims to resolve the fundamental interactions between solar magnetic fields and the dynamic atmospheric plasma on scales below 0.1 arcsec over entire active regions.

The ATST is a collaboration of 22 institutions, reflecting a broad segment of the solar physics community. 

 the National Solar Observatory is an American observatory operated by the association AURA.

The mission of the National Solar Observatory is to advance knowledge of the Sun, both as an astronomical object and as the dominant external influence on Earth, by providing forefront observational opportunities to the research community. The mission includes the operation of cutting edge facilities, the continued development of advanced instrumentation both in-house and through partnerships, conducting solar research, and educational and public outreach.