The photo shows David Lunt in 2001 in front of his office in Tucson, Arizona. An obituary with a short biography of David Lunt can be read on Sky & Telescope.
His H-alpha telescopes revolutionized solar observing as they were the first affordable instruments of their kind. The H in H-alpha stands for hydrogen. H-alpha is a specific wavelength of light emitted by hydrogen atoms in the Sun. The wavelength of this light is 656 nanometres, falling within the red part of the spectrum.
A layer lying above the solar atmosphere’s photosphere becomes visible H-alpha light. This is called the chromosphere, as it appears as a red, coloured fringe during total eclipses.
The photosphere is the source of all visible light from the Sun and can be observed through telescopes using classic white light neutral density filters. The famous ‘eclipse glasses’ can also be used to view the photosphere.
While the photosphere normally shows few or more spots, depending on solar activity, there is always something going on in the overlying chromosphere to observe: prominences, much larger than our Earth, are visible at the edge of the Sun and as dark filaments above the solar disk. Bright flares - violent outbreaks of radiation - accompany the dark sunspots. This ‘scenery’ changes from day to day, or even within just a few hours, which adds to the fascination of solar observing in the H-Alpha region.