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Solar Chromosphere Imaging

Sommers-Bausch Observatory, University of Colorado at Boulder

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The Sun in Hydrogen-Alpha

Live streaming of the solar chromosphere was broadcast intermittently through May 19th - daylight hours and weather permitting. Continuous imaging began at Noon on May 20th 2012 with occasional interruptions to utilize the heliostat in alternate modes.

Uninterrupted partial solar eclipse coverage started at 6 pm MDT. First contact occurs at 6:22 pm. The heliostat loses line-of-sight to the Sun around 7:18 pm (9 deg altitude) due to obstructions. Maximum eclipse (86%) occurs a few minutes later, at 7:30.


During the eclipse SBO may interact with the CU Folsom Stadium Eclipse Party in pointing out solar features; activity will be explained in the scrolling text.


Live stream by Ustream
This free Ustream webcast is paid for by the commercials which appear from time-to-time on your screen.

Ustream Premium Members who log into their account can watch ad-free by searching for Colorado Astronomy and/or the channel SommersBauschObservatory Heliostat.

SBO is also streaming images of the solar photosphere on May 20th: see the SommersBauschObservatory Dome channel.


NOTE: Click the "enlarge" button, lower-right corner of the window, to view the solar image full-screen.

What You Are Seeing

You are looking at live images of the Sun from the heliostat (solar telescope) at Sommers-Bausch Observatory, [Department of Astrophysical & Planetary Sciences, University of Colorado, Boulder]. Telescopes invert images top-to-bottom and left-to-right; hence, south is up in these images, while west is to the left. Users watching the eclipse with mylar sunglasses will see the first "bite" taken out of the Sun from its western (lower-right) edge; that "bite" will appear at the left side of the image here.

The Sun's light is focussed through a Halle-Lyot birefingent filter, which blocks all colors except the deep red light emitted by hydrogen atoms at temperatures of around 20,000K (degrees Kelvin). This light occurs at at a precise wavelength of 656.3 nanometers, and is known as "hydrogen-alpha" emission.

Images of the Sun at this wavelength show the tenuous outer atmosphere of the Sun which overlies the cooler (6,000K) visible photosphere ("sphere of light") where sunspots occur. This region is called the chromosphere, meaning quite literally "the sphere of color" - the red color of the hydrogen atom emission.

Normally the chromosphere is only visible for a few brief minutes during a total solar eclipse, and then only that portion that exends beyond the edge (limb) of the Sun. Only in the last century have astronomers been able to see the chromosphere from "above", looking down onto the disk and at times other than during an eclipse.

Features in the Solar Chromosphere

Historical Connection

Some of the very earliest hydrogen-alpha solar recordings were made in the late 1940's by Harvard College's High Altitude Observatory (HAO) using the western hemisphere's the first solar chronograph. The facility was located at Climax, Colorado, at 11,000 feet elevation, and staffed by Walter Orr Roberts and Jack Evans (who perfected the modern Lyot filter design). HAO moved its headquarters to Boulder in the early 1950's and became affiliated with the University of Colorado. Sommers-Bausch Observatory was constructed for joint HAO-CU solar observations from down here "on the flats" in 1953, and became the foundation for CU's Astro-Geophysics (now Astrophysical & Planetary Sciences) Department. SBO's founder and first director was Dr. Walt Roberts.

Sommers-Bausch Observatory is renewing its 60-year-old mission as a solar observatory through its recent acquisition of a Halle H-alpha filter, once used to monitor the Sun for flares as part of a safety net for the Apollo lunar astronauts. The Observatory's acquisition of this exquisite filter made possible by the dedicated and enthusiastic efforts of Dr. Alan Kiplinger, and the the generosity of the Space Environment Center of the National Oceanic and Atmospheric Administration (NOAA).