The Ventura County Astronomical Society holds monthly meetings on the third Friday. Their venue includes club business, astronomical highlights of upcoming events, and guest speakers.
Today the discussion started with information on telescopic mathematics. Dave Holland mentioned the importance of three measurements every astronomer who owns a telescope should know. They are:
Focal length is defined as the distance from the optical center of a lens (or optical system) to its point of focus when focused at infinity. http://www.chuckhawks.com/telescope_focal_length.htm
Focal Ratio is the ‘speed’ of a telescope’s optics, found by dividing the focal length by the aperture. http://www.astronomics.com/main/definition.asp/catalog_name/Astronomics/category_name/tajf859xqdpqa8l1jqu/Page/1
Aperture is the size of the main optical lens of the telescope.
All three require only simple calculations. For example, taking the focal length of a telescope and dividing it by the power of the eyepiece yields the true magnification of the object viewed. Hence, a 2350mm focal length divided by a 26mm eyepiece produces 90x magnification.
Our guest speaker from JPL, Dr. Marc Rayman spoke about close up views of asteroids, thanks to the Dawn project. The ability to reach the asteroid belt is made possible by star wars technology.
Ion propulsion of spacecraft has given us the asteroid belt. Currently the Dawn project is orbiting Vesta, an asteroid smaller than Ceres, but still map-able. Dr. Rayman, who is in charge of the Dawn project gave an enlightening talk about Xenon, the gas used as propellant, and the necessity of solar panels on the craft to power the production of ions. The use of ion drive is limited only by its the distance from the sun, since the craft requires solar energy as well. Nevertheless, the space gymnastics required for the trip to the asteroids has been made possible only because of ion propulsion. Next stop, Ceres.
Meetings so rich in information are well worth the $35 annual membership fee.
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