Optical Surfaces Ltd. of Kenley, Surrey, has delivered three high-precision off-axis parabolic mirrors to the Big Bear Solar Observatory in Big Bear Lake, Calif., USA. The reflectors will form key focussing components in the adaptive optical system associated with the observatory’s new 1.6-m solar telescope.Three high-precision off-axis parabolic mirrors will become focussing components in the optical system of this solar telescope.Scheduled for completion later this year, the Gregorian solar telescope will be the world’s largest telescope and will enable precise studies of the physics of the sun and observation of solar phenomena. It relies on adaptive optics to provide imaging corrected to the diffraction limit. It also features advanced computer systems that can support sophisticated instruments such as Fabry-Perot interferometers, which enhance observation at infrared wavelengths. The adaptive optics will allow imaging of photospheric flux tubes at about 100-km resolution.