Summary of the Apparent Motion of the Stars

1
Summary of the Apparent Motion of the Stars

• From Syracuse, NY looking North
• From Syracuse, NY looking East
• From Syracuse, NY looking South
• Reference to a Figure 1.4 in the text
• The five rules regarding the apparent motion of
  the stars.

2

• Looking North
• Stars appear to circle CCW around Polaris (NCP)
  once every 23h 56m 4.09s
• Stars from the NCP to ( 90?-Obsr. Lat) are
  circumpolar e.g. in Syracuse, 43?lat stars from
  90? to 47?declination are circumpolar
• Non-circumpolar northern stars are above the
  horizon from 12 to just under 24 hours.

Lat of Obsr.
3

• Looking East
• Stars rise all along the eastern horizon along
  paths that slant towards the south.
• The slant angle of rising stars relative to the
  vertical is equal to the observers latitude (i.e.
  43?
• Stars complete one cycle around the sky once
  every 23h 56m 4.09s
• Stars near the celestial equator spend about 12
  hours above the horizon.

4

• Looking South
• Stars to appear to move along down-curving
  circular arcs from east to west (CW)
• Stars complete one cycle around the sky once
  every 23h 56m 4.09s
• Stars in the southern celestial hemisphere spend
  less than 12 hours above the horizon.

5
Fig. 1.4
This figure from the text, also summarizes the
apparent motion. Remember that our goal is not
to just describe the motion, but to quantify it
by attaching relevant numerical quantities to the
apparent motion of the stars.
6
The Five Rules for the Apparent Motion of the
Stars

• 5. At mid-northern latitudes the time a star
  spends above the horizon is as follows
• Northern stars gt 12 hrs
• Stars near the celestial equator 12 hrs
• Southern stars lt 12 hrs

4. Stars in the south move along downward
curving arcs. The southernmost visible
declination is (obser. lat 90)
3. Stars rise along the eastern horizon at an
slant angle toward the south from the vertical
equal to the observers latitude.
2. The circumpolar region extends from Polaris
down to a declination equal to (90 - obser. lat)
1. The altitude of Polaris equals the observers
latitude and all stars rotate ccw around Polaris