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20 SEP

NEXT EVENT VOL 21

A series of talks from September 20-25, 2018. More details to follow. 


The autumnal equinox is at ecliptic longitude 180° and at right ascension 12h. 

equinox is a moment when the vernal point, celestial equator, and other such elements are taken to be used in the definition of a celestial coordinate system. The position at other equinoxes can be computed by taking into account precessionnutation, and aberration, which directly affect e.g. right ascension and declination.

Contrastingly, epoch is a moment for when a given position of an astronomical object is valid. The position at other epochs can be computed by taking into account proper motionparallax, and orbital elements.

In the case of orbital elements for objects within the Solar System, only a few of the classical orbital elements are affected by a switch of equinox: the longitude of the ascending node and (to a much lesser extent) the inclination. If another set of orbital elements are used, such as the position and velocity vectors for a particular epoch, all components can be affected by a switch of an equinox.

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Clowns Without Borders

BY BRUCE MACPHAIL
@ VOL 11 ON FEB 19, 2010

Bruce Macphail is the project manager for the American chapter of Clowns Without Borders, and in his presentation he discusses the CWB's mission to offer laughter and relieve suffering for all who live in areas of crisis, especially children.

"Presentation of the Day" on January 18, 2013.

 

WASHINGTON DC Blog

Clowns Without Borders

In our last "Presentation of the Day" for the week, we meet Bruce Macphail, the project manager for the American chapter of Clowns Without Borders. In his presentation (from PKN Washington D.C. Vol. 11) he discusses the CWB's mission to offer laughter and relieve suffering for all who live in areas of crisis, especially children.

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