Date: July 11, 2011

Title: Stargazing and Our Atmosphere

Podcaster: Maurice Kemp

Organization: Maurice Kemp Photography

Links: http://mauricekempphotography.weebly.com

Description: Originally, man’s naked-eye view of the stars was significantly distorted by our precious atmosphere. The overall height of our atmosphere, made up of multiple layers, was well beyond his escape. Despite the inconvenience of our life essential atmosphere, man has gained an amazing optical view of the stars which began with a small optical telescope in the 1600s which led to much larger earth based observatories which ultimately amounted to the placement of optical telescopes in a low earth orbit outside the distortion of our atmosphere.

Bio: Maurice Kemp is a professional photographer – http://mauricekempphotography.weebly.com. Maurice Kemp studied electrical engineering at the University of Texas at San Antonio which complemented his experience in the Air Force where he was assigned to the Radiation Science Division – High Energy Department as an electronic technician. Both his academic studies and work experience in his early twenties honed his appreciation for the properties of electro-magnetic energy; especially visible light and how how it is transmitted, absorbed and reflected by its environment it’s this appreciation that continues to drive his interest in astronomy.

Sponsor: This episode of “365 Days of Astronomy” is sponsored by midnightmartian.com: 3D apps for the iPhone, iPad and iPod Touch.

Transcript:

Welcome to the 365 Days of Astronomy Podcast. I’m Maurice Kemp – Amateur Astronomer.

There are an interesting host of celestial bodies and objects that exist on the opposite side of the Earth’s atmosphere from where we stand. Celestial bodies such as the sun, the nearest star and governing body of our solar system, the moon, the Earth’s only natural satellite, the stars, point sources of light that allowed man to navigate beyond his line of sight, and wandering stars, the planets, that captured man’s curiosity because of their seemingly irregular paths, all served to drive man’s desire to learn more about the worlds beyond the reach of everything to include his naked; everything except his imagination.

Long before early man’s imagination began to truly focus on the nature of stars, his view of them was unknowingly distorted. He had no idea that his naked eye, which was subject to the Earth’s atmosphere, could only accommodate the apparently largest and brightest stars in his night sky. And so, he would have only been able to count 2 to 3 thousand of the 200 billion stars that make up the Milky Way – our galaxy.

With Civilization, a few men had the opportunity to pay closer attention to the stars. They took note of their seemingly fixed arrangements, the pattern of their movement in the skies over time and their general appearance. Their improved understanding of stars helped developed their concept of time and their understanding of seasonal changes In search for the origin and meaning of life, man imaginatively associated constellations, with their gods, people and animals of their stories and myths. Today, most of the naming conventions for stars and constellations that have survived are of Arabic, Greek and Roman origin. .

Historically, the heavens fed the imagination of men and provided them clarity about the nature of the world around them. The clarity of celestial bodies and objects depend on atmospheric conditions and limits of the naked eye.

The naked eye is unable to detect light if it’s too dim. Celestial bodies vary in brightness. The brightest celestial body is our sun followed by the moon. A much dimmer celestial object is the Andromeda Galaxy and one of the dimmest bodies detectable by the naked eye is Uranus. To uniformly categorize the apparent brightness of celestial objects, a scale was formalized based on the star Vega which expresses units of brightness in magnitude. Vega has an apparent magnitude of 0, brighter objects are negative and dimmer objects are positive. Our sun has an apparent magnitude of -27 and our full moon has an apparent magnitude of -12.

The faintest or dimmest light detectable by the human eye is approximately negative 6 magnitude under optimal conditions which is anywhere away from light pollution of the city..

Our atmosphere is structured in 5 principle layers and is held in place by our planet’s gravity., it moderates extreme temperature changes between day and night, absorbs UV radiation and provides essential warmth for life through the greenhouse effect; allowing light to pass while trapping the heat that radiates from the Earth’s surface The 5 structural layers of our atmosphere are the troposphere, stratosphere, mesosphere, thermosphere and the exosphere. Each layer is dynamic and plays a major role in protecting life on our planet. The dynamics of these layers also impact electro-magnetic radiation to include light. Our atmosphere dynamically scatters, refracts, transmits, absorbs and reflects the light of celestial bodies that travels through it in route to our eyes. Dynamic scatter results in our skies changing color from sunrise to sunset. Dynamic refraction of our atmosphere is why celestial bodies such as planets blur and stars appear to twinkle. Astronomical seeing defines the blurring and twinkling of celestial objects such as stars caused by turbulent mixing in the Earth’s atmosphere which is a phenomenon that varies its optical refracting index.

The astronomical seeing conditions vary with time and with location. Astronomical seeing is expressed as seeing disc and measured in arc-seconds. Optimal Seeing provides the lowest measure of arc-seconds possible such 0.5 arc-seconds which is achievable at locations such as Mauna Kea. This location is high, dry, cold and potentially very dark at night.

The challenge of viewing celestial bodies and object beyond the scope of the naked eye was met 400 years ago. In 1608 , Hans Lippershey is generally credited for pairing a concave and convex lens to form the first crude telescope. Though it is possible that someone else may have been first such as Sacharias Janssen, a competitor of Lippershey, Lippershey did do recognizably more to promote the new technology; selling it to the Dutch government for military purposes. In 1609, Galileo Gallilei is given credit for demonstrating its usefulness in the world of astronomy. Observing celestial bodies on the opposite side of our atmosphere with the aid of his plano-convex plano-concave telescope revealed details undetectable by the naked eye. In particular, Galileo’s observations of the planet Jupiter yielded an unimaginable discovery. On 7 January 1610, Galileo observed Jupiter was flanked by a straight line of three small bodies Continued observations revealed the bodies were moving toward and away from Jupiter. On 13 January, Galileo observed a fourth body.

Galileo concluded the four bodies were moons orbiting Jupiter. In March 1610, Galileo published a pamphlet titled, SIDEREUS NUNCIUS in which he revealed the details of his revolutionary observations. 400 years of evolution shaped the telescope into an amazing tool. What started as two pieces of refracting glass that crudely focused light to multiple focal points depending of the wavelength of light, served as the inspiration for the parabolic and planar mirror that reflected and focused light. This reflecting telescope was designed by Scottish Astronomer, James Gregory, in 1663 and the first model was built by Sir Isaac Newton in 1688.

Both telescopes produce unique forms of optical aberrations and both aberrations are correctable to a certain degree. Whether its the chromatic aberration of the refracting telescope or coma aberration of the reflecting telescope, both telescopes improve the range of celestial bodies that can be observed by the naked eye. Both telescopes were subject to size limitations Rigid optics have upper size limits due to their tendency to deform under their own weight As industry and technology improved the telescopes were built larger and larger to collect more and more light to observe wider range of celestial bodies. Another innovation displaced the human eye, one of the original limiting factors, with a photographic camera in 1880.

This allow for long exposure images, an idea introduced by Astrophotographer John Draper, of very low light that made very faint celestial bodies and objects viewable for the first time. The improved telescopes were still subject to the astronomical seeing of our atmosphere. The first effort to reduce astronomical seeing was to reduce the amount of light passing through it by viewing space from a higher altitude. The Hooker telescope which first saw light in November 1917 was the first to apply the solution of large optics and high altitude to improve our image of celestial bodies and objects. Other notables telescopes are the 200 inch Hale telescope in California, the 6 meter BTA-6 in the Caucus moutains in Russia, 10 meter Keck 1 in Hawaii and the 10.4 Gran Telescopio Canarias on the island of Las Palmas, in the Spanish Canary Islands. Adaptive optics are also used to correct for atmospheric seeing along with reducing the amount of atmosphere between us and celestial bodies by setting up telescopes at higher altitudes. The most impressive effort to eliminate atmospheric seeing was to put a telescope in space. In April of 1990, less than 400 years after the first telescope, the Hubble Space Telescope was carried into space by Space Shuttle Discovery, mission STS-31, where it was placed in Near Earth Orbit. With an orbit period of 96 to 97 minutes, the Hubble Space Telescope employs amazing technologies to capture still images of celestial bodies and objects. Designed to be serviced in orbit, the Hubble Space Telescope has been services 5 times and is expected to remain in orbit until 2014. Four years later the Hubble Space Telescope is scheduled to be replaced by the James Webb Space Telescope which is designed to orbit for 5 years with a goal of 10. The James Webb Space Telescope will provide incredible images of space using 3 anastigmat photographic lenses. I am Maurice Kemp; just an amateur astronomer, and I hope that as our view of our amazing universe grows clearer and clearer so will our understanding of it as well as each other. Thank you for listening to my podcast and good bye for now.

End of podcast:

365 Days of Astronomy
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