Supergalactic coordinate system - a simple definition<BR>
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For studies of more distant extragalactic objects, the most natural 
coordinate system is supergalactic coordinate system. The reference plane of 
this system is defined by <I>Gerard de Vaucouleurs</I> as the plane where 
density of galaxies in our environment is the largest.<BR>
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Supergalactic longitude, SGL, is measured counterclockwise from direction 
l = 137.37 deg, b = 0 deg. The values are between 0 and 360 degrees in 
decimal format (degrees).<BR>
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Supergalactic latitude, SGB, is measured from the supergalactic plane, 
positive northwards and negative southwards. The values are between -90 and 
+90 degrees in decimal format (degrees).<BR>
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