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David Haworth
"Observing the Small White Dots - The Analysis of Starlight"
November 21, 2011

Here is a pdf of his talk
Here is a YouTube Presentation of his talk

Astronomical spectroscopy began with Isaac Newton's initial observations of the light of the Sun, dispersed by a prism. He saw a rainbow of color, and may even have seen absorption lines. These dark bands which appear throughout the solar spectrum were first described in detail by Joseph von Fraunhofer. Most stellar spectra share these two dominant features of the Sun's spectrum: emission at all wavelengths across the optical spectrum (the continuum) with many discrete absorption lines, resulting from gaps of radiation.

Astronomical spectroscopy provides a way to analyze the starís chemical composition, temperature and its radial velocity. Spectroscopy is the analysis of star light dispersed according to its wavelength. This light dispersion is called a spectrum and it is displayed as white streaks or color streaks in an image.

A common example of a spectrum that most people have seen is a rainbow that is created by the Sun and the rain.

Davidís presentation starts with an overview of the basics types of spectrums.

He will show you how to build a simple solar spectroscope that shows that the Sunís photosphere is composed of hydrogen, sodium and magnesium. A moderate resolution spectrum of the Moon and planets are analyzed next.

Moving father from Earth an introduction to spectral classification is covered with examples of standard spectral type stars taken with a simple grating filter. Also, the spectrum of stars is compared to a nebula spectrum.

Finally an image like the one on the right will be analyzed showing unique objects such a very cool temperature infrared star and the redshift spectrum of a Quasar that is 3.269 billion light years away

David Haworth enjoys astronomy, astrophotography and processing images to bring out details that cannot be seen by visual observing. David started in astrophotography in 1996 and he has used a variety of cameras to image the sky.

David wrote "Afocal Photography with Digital Cameras" chapter in the second edition of "The Art and Science of CCD Astronomy" book and "Flat Field Calibration using an LCD Monitor" article in AstroPhoto Insight magazine. David's images have appeared on a magazine front cover, in magazine articles, a book front cover, in books, in catalogs, in videos, on posters, on music CD covers, on T-shirts, on wine bottles and on a variety of web sites.

Recently, David has been using spectroscopes to analyze the light from celestial objects that range from the Sun to distant Quasars that are billions of light years from us.

More information available at http://www.stargazing.net/david/spectroscopy/index.html

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