Top of the McMath-Pierce Solar Telescope.

The heliostat of the McMath-Pierce Solar Telescope at Kitt Peak National Observatory (KPNO), a Program of NSF NOIRLab. The heliostat has a 2.03-meter (80-inch) mirror that reflects sunlight into the optical path of the telescope. The McMath-Pierce Solar Telescope was the largest solar telescope in the world upon its completion in 1962, a title it held until the first light of the National Solar Observatory’s Daniel K. Inouye Solar Telescope in December 2019. The interior of the McMath-Pierce Solar Telescope is currently being renovated to become the Windows on the Universe Center for Astronomy Outreach.