Celestial Star Globe
The Celestial Globe is a demonstration device that shows the apparent positions of the stars visible from Earth. The three dimensional representation allows the relative angular positions of the constellations to be visualized and permits students to estimate which stars will be visible from different places on Earth for any rotational position of the planet.
The globe consists of two concentric spheres mounted on a common axle and supported on a frame with a base.
The inner sphere (1) in the above illustration) is 4” in diameter and represents the Earth. The continents are marked on it in their correct relative positions. The outer sphere (2) is transparent. It is 12.5” in diameter and has the constellations and their stars marked on it. Yellow shading indicates the Milky Way, the plane of our galaxy. The axle (3) that carries both spheres allows them to be rotated independently.
An angle scale is marked on the frame (4) that supports the axle. The angles are marked every degree and extend from zero at the equator to 87° in both directions. The frame is fixed to a round base (5) so that the axle is held at an angle of 23.5° to the vertical, representing the inclination of the Earth’s spin axis to the axis of its orbit around the sun.
The Celestial Globe is a demonstration device that shows the apparent positions of the stars visible from Earth. The three dimensional representation allows the relative angular positions of the constellations to be visualized and permits students to estimate which stars will be visible from different places on Earth for any rotational position of the planet.
The globe consists of two concentric spheres mounted on a common axle and supported on a frame with a base.
The inner sphere (1) in the above illustration) is 4” in diameter and represents the Earth. The continents are marked on it in their correct relative positions. The outer sphere (2) is transparent. It is 12.5” in diameter and has the constellations and their stars marked on it. Yellow shading indicates the Milky Way, the plane of our galaxy. The axle (3) that carries both spheres allows them to be rotated independently.
An angle scale is marked on the frame (4) that supports the axle. The angles are marked every degree and extend from zero at the equator to 87° in both directions. The frame is fixed to a round base (5) so that the axle is held at an angle of 23.5° to the vertical, representing the inclination of the Earth’s spin axis to the axis of its orbit around the sun.
The setup is easiest using the vernal equinox. At this point in time, the sun crosses the celestial equator going north and the stars' right ascension of zero hours (the Prime Meridian) is lined up with the Earth's axis as seen from the sun. So shine a "sun" (Flashlight) directly at the Earth's equator at the Earth's vernal equinox position then rotate the celestial globe so that zero on the RA scale is in line with the beam and the earth's axis. You now have the stars' positions at the vernal equinox (approx. March 20 - beginning of Spring) and can move the celestial globe around by 2h RA per month (or 6h RA per season) to find other views. The day/night views are seen by viewing the celestial sphere from different positions around the globe relative to the "sun."