These notes are hints for using the Celestial Globe - all these topics
are covered in detail in the lab, itself.
0 Note the Earth inside the globe - this is a geocentric, earth
centered, view of the
universe.
1 Locate:
the Earth’s axis - where does it emerge from the
celestial globe?
the Celestial Equator - seam on the globe
the ecliptic - turn the
knob which moves the Sun
- observe the path that the Sun traces
Note the line the Sun traces and the dates on the
line - this is the ecliptic, the path of the Sun over the year.
The celestial meridian - this is the thread that we
added to the Star Finder. When the Sun crosses the celestial meridian
what time is it?
The horizon ring - note the cardinal points, N, E,
S, and W and the azimuth printed on the horizon ring.
Azimuth is measured along the horizon ring from the
north (0°), to east (90°), to south (180°), ...
What letter, i.e. direction, is printed at 270°?
The zenith - over head point - top of the celestial
globe no matter how it is set
2 Measurements you will need on the Globe
Declination, abbreviated DEC, analogous to latitude
on Earth. Measured in degrees.
Right Ascension, abbreviated R A, analogous to
longitude but on measure eastward. Note: R A is measured in
hours, minutes and
seconds.
DEC and RA are required to locate objects and place
objects on the celestial globe (just like latitude and longitude on
earth or steet and avenue in Manhatten).
3 Setting Location on earth to NYC - latitude - adjust height (40°
for NYC) and direction of the
north star. Make sure
the north star, Polaris, is above the N on the
horizon ring, i.e. north.
- longitude -
twirl the Earth so that the longitude of interest, NYC,
is directly under the zenith - the high point of the globe.
4 Setting the date - Place the Sun on the appropriate date on the
ecliptic.
5 Setting the time - we are people of the Sun, so holding the Sun at
the specified date position the Sun to set the time.
For 6 AM or sunrise place the Sun on the eastern
horizon, for noon place the Sun under the celestial
meridian, for midnight place the Sun at the lowest point on the
globe, opposite the noon position. Where would we place the
Sun
at sunset?
(We will use 6:00 A.M. as sunrise, although in spring and
summer it is earlier and in autumn and winter later.
Similarly, we’ll use 6:00 P.M. as
sunset.)