Star Points for January, 1999; by Curtis Roelle Celestial Bearings The basic cardinal directions of east, west, north, and south delineate the domain of the flat lander earthling. When the gaze turns upward to a constantly changing sky these compass points quickly become inadequate. Don't dismiss these normal directions too quickly because they are important to astronomers. But so are a number of other standard references. They are necessary because space is not flat. It extends in three dimensions beyond the visible universe and for most purposes can be approximated by considering it to be infinite. Although the stars and galaxies scattered across the sky are at various distances for mapping purposes it is convenient to consider the sky as if it were painted onto the inside of a globe or "celestial sphere." This is not as extraordinary as one might think. For instance, when was the last time you opened a highway map and found it had mountains rising out of the paper? (Topographic maps do model the terrain. Likewise, specialized star atlases exist which provide information about a star's true distance and motion for those who require it. However, most people require neither map for general purposes.) When you are standing outside admiring the celestial sphere the point directly over your head is called the "zenith." Since the earth is curved no two person will have the exact same zenith (unless one is standing on the other's shoulders). The lines between each person and their respective zeniths are not parallel. Think of the zenith as being the point where a line perpendicular to earth passes through the top of your head and intersects the celestial sphere. By the way, the opposing point directly beneath your feet is known as the "nadir." Assuming a spherical earth, all nadir lines intersect at its center. According to the Dictionary of Astronomical Terms (by ke Wallenquist) nadir is "the point where a vertical line extended underfoot meets the celestial sphere on the other side of the earth." Turning around you observe the horizon in all directions. The celestial sphere appears to meet the ground at the horizon. Now, imagine that you could paint a line directly onto the celestial sphere. Beginning due south at the horizon draw your line up the sky and through the zenith, then continue downward until you reach a point on the horizon marking due north. This line is the "meridian". It divides the sky into east and west. When a star rises in the east it gets higher and higher until it "transits", or crosses, the meridian. It then gets lower and lower until it sets in the west. So now in addition to the cardinal directions you are now familiar with the celestial sphere, the zenith and nadir, and the meridian. In a future discussion we will build on these to add more to our astronomical nomenclature. Astrophotography is the art (or is it a science?) of photographing celestial objects. An astrophotography contest for members of the Westminster Astronomical Society will be held at the January meeting at 7:30 p.m. January 13 at the Bear Branch Nature Center north of Westminster. Visitors are welcome and are in fact encouraged to attend. Your questions, comments, criticisms, and suggestions are encouraged via e-mail to StarPointsUSA@yahoo.com.