Star Charts 101. North is ordinarily
at the top of a map, south is at the bottom, east is to the right, and
west is to the left. If you look down on a map oriented so that north
on the paper lies in the same direction as north on the earth, then east
is to your right and west is to your left. But if you look down on
a star chart, as above, with north at the top of the page, then east is
to your left and west is to your right. These directions are reversed
because star charts are intended to be held overhead as you view them.
If you face north and hold our current chart overhead, then west on the
chart and in the sky is to your left, and east is to your right.
If you hold the map overhead and orient it toward whichever direction you
are facing, then any direction on the map will match the corresponding
direction in the sky and on the earth.
Our current chart shows the whole sky
at 8:00 PM on January 20. The zenith is near the middle of the chart,
and the perimeter of the chart marks the horizon. Jupiter (mag -2.6)
and Saturn (mag 0) remain high overhead near the Pleiades. Venus
continues shining brightly in the west at mag -4.3, nearing its maximum.
Orion is better placed as winter wears on, rising about a degree higher
every night - about 30 deg per month - along with everything else in the
sky. In the course of a year, the stars will again be in their present
positions, within arcseconds, but the planets are less easily predictable. |
