The use of planisphere to locate planets

The accuracy of this method to locate the planets using the planisphere is accurate to a few degrees because the planets are within a few degrees from the ecliptic plane. Even with a minor discrepancy, the accuracy is good enough for us to use the planisphere to locate the planets. Such accuracy is better than just indicating the positions of the planets by making reference to constellation only. In the example in Figure 4, Virgo extends more than 30 degrees along the ecliptic. The intersecting point of Virgo with the ecliptic is in fact toward one of its ends near the Leo. If we only specify the position of the planet to be in Virgo, the uncertainty of its exact location is much greater.

Pedagogically, this method requires higher order cognitive skills as compared with the way to obtain the location of the planets from reading off the information from tables. First, students need to understand that the planet orbits are nearly coplanar and close to the ecliptic. Next, they also need to exercise their spatial thinking skill to determine the intersection of the ecliptic plane with the horizon. The thinking process helps students to develop and consolidate the concept of the celestial sphere as seen from the surface of the earth.

There are many misconceptions held by students about the planets and the solar system (Sadler 1992). Misconceptions are hard to alter. To change the misconceptions by simply presenting the correct concepts through lectures and reading text are not effective. Only when learning involves high order thinking skills and students' knowledge is challenged, the concepts could then become internalized. Thus instructional strategies should include learning activities which require higher order cognitive skills in order for students to reconstruct their own knowledge. In view of this, by extending the application of the planisphere to locate planets, a practical learning activity introduced in this article, could be a useful tool for such purpose.