Optical telescopes are the most recognizable, as they are very similar to those you use in your own backyard. Optical astronomy provides both the most breath-taking images we see and the most basic information we know about our solar system, the Milky Way, and all the galaxies surrounding us.
Optical astronomy is limited by both the relative narrowness of the optical spectrum and the fact that the Earth's own atmosphere blocks out and bounces around some of this light, distorting the image we see. The human presence is also a problem for optical observing, as light pollution also severely limits the quality of data you can collect. Because of this, observatories are usually located in places with a low percentage of daily cloud cover (less clouds = more observing), away from towns and city (less light pollution = better observing), and normally at high altitudes (less atmosphere = less scattering).
Given these limitations, space-based observatories (such as Hubble) give clearer images, and better quality information about the objects. However, putting a telescope in space is a difficult, time consuming and very costly practice. As such, a lot of advancements in the field of optical astronomy have been focused on terrestrial based observatories.
Solar Corona: CoronagraphsLast Updated on 2007-12-26 00:00:00
For thousands of years, humans had stared at the sun during total eclipses, marveling and even trembling at the halo of greenish light that surrounded the blackness like the iris of some malevolent eye. The likeness to a human eye was not lost on civilizations as ancient as the Egyptians, and for whom the vengeful Eye of Horus may have been its antecedent. But to study this ineffable glow in more detail, only the rare total solar eclipse provided the means. By the late 1800’s astronomers and solar observers realized that the corona was the key to understanding many solar phenomena, perhaps even the mysterious aurora borealis themselves.
Bernard Lyot sitting at his Coronagraph at the Pic du Midi observatory in France ca 1939. (Courtesy: American Museum of Natural History.)
In 1930, Bernard Lyot (1897-1952) invented an instrument that allowed total solar eclipses to be recreated at... More »
Wisconsin H-alpha MapperLast Updated on 2007-10-03 00:00:00
The Wisconsin H-alpha Mapper (WHAM) is a small, remotely controlled astronomical observatory, funded by the US National Science Foundation and dedicated to the detection and study of faint emission from atoms and ions within the diffuse, low-density warm ionized gas that permeates the disk and halo of the Milky Way. This wide-spread, 2000 pc thick plasma layer is characterized by densities of order 0.1 cm-3 and temperatures near 8000 K, and it accounts for most of the ionized hydrogen in the interstellar medium. The ionization is likely produced by Lyman continuum radiation that somehow leaks away from O stars and classical emission nebulae in active star forming regions.
As its first major mission while located at Kitt Peak National Observatory near Tucson, WHAM completed a 37,565-spectra H-alpha emission line survey of the northern sky above declination -30 degrees. This survey,... More »
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