The Cosmic Explorer
(600-2409)                 Alignment                  Faxback Doc. # 33043

Alignment Instructions:

The basic information you need to align the Star Ball for a night's
observing is printed here, at the E and W cardinal points.  The Equator
should always be positioned at the E (90 degrees) and W (270 degrees)
points for proper orientation.  You can see a finely printed scale which
is 47 degrees long at the E and W regions of the Horizon Ring.  This scale
helps to make sense of the wanderings of the Ecliptic.  For example, if
you want to see where on the horizon the sun will rise on the first day of
summer, ~ 21, position the sky calendar so that the date June 21 is
aligned with the Eastern Horizon.  If you keep the equator aligned at 90
degrees and 270 degrees, you will see that the sun rises 23.5 degrees N.
Try this for the other three major seasonal dates.  Only on ~ March 20 and
~ September 21 does the sun rise and set at the E and W points.  This
migration of the sun North and South of the E and W points gives us our
seasons.

Zenith:

The zenith is the highest point in the sky.  Each observer has his or her
own zenith.  If you are standing outdoors, your zenith point is directly
overhead.  The Earth's atmosphere is thinnest in the direction of the
zenith so stars, planets, and other objects look brightest there.  The
declination at your zenith equals the latitude of where you are on Earth.
If you lived at the North pole, the North Star would be almost exactly at
your zenith.

Right Ascension and Declination:

To help locate, describe, and chart the motion of objects in the Universe
around us, astronomers have adopted a system of map coordinates not too
different from what is used in geographic maps.  Essentially, astronomers
divide the sky into a North Celestial Hemisphere and a South Celestial
Hemisphere.  This is done by using the Celestial Equator, just like the
Earth's equator which divides the Earth into two geographic hemispheres.

Circles of Latitude are added to the Earth's map: similarly, circles of
Declination (Dec) are added to the sky map.  In both cases, the distance
of a place on Earth or sky from its Equator is measured North (+) or South
(-) in degrees ( degrees) minutes (') and seconds (").  Your Degree Scale
is used to locate Dec values on the Star Ball.  More on this later.

Declination fixes North and South directions.  To locate objects East and
West on Earth, a fixed meridian or reference arc is established and a
series of arcs are drawn from the North Pole to the South Pole, crossing
the equator at right angles.  These arcs are called lines of longitude and
are usually shown 15 degrees apart.  The same sort of thing is done with
the Star Ball.  The fixed point selected to begin the celestial-type of
longitude is the intersection of the Ecliptic and the Celestial Equator.
To distinguish measurement of this direction from that of latitude, we use
hours (h) instead of degrees, minutes (m) instead of minutes ('), and
seconds (s) instead of seconds (").  Finally, this coordinate is called
Right Ascension (RA), it starts with 0^h (or 24^h) and always increases
EASTWARD.

That's it!  With these two simple coordinates, we can assign to anything
we can see in the sky a fairly permanent address that anyone who can read
numbers-no matter what language they speak and write-will be able to find.


(BR/EB 5/10/96)