High Altitude Solar Observatory facility at Mauna Loa, Hawaii. The Low Angle (LOWL) telescope (at lower left) measures the oscillation of the Sun. The Coronameter telescope (seen through the large dome's opening) observes the white-light component of the Sun's outer atmosphere (corona). LOWL meas- ures the Sun's oscillations as frequency changes (Doppler shifts) in light from its moving surface. The Coronameter blocks out the brightness of the Sun's disk which normally drowns out the corona around it. Coronagraphs such as this are always placed on sites at high altitude to reduce atmospheric scattering of the incoming light.