Planispheres

TITLE:

Observational astronomy with naked eye and planispheres

For groups of ideally ~8 students (larger groups can be divided for telescope time), over 45 minutes' time

GOALS:

• Understand the rotation of the earth around its axis and the earth around the sun
• Gain familiarity with night sky features
• Understand why the night sky changes over time
• Be able to locate major constellations
• Operate a planisphere

INSTRUCTIONAL PROCESS:

PREPARATION

Materials

• planispheres
• green laser pointer
• binoculars if available
• red flashlights
• blankets and sweatshirts

Setup

• none

INTRODUCTION/ENGAGEMENT:

• Gather students in warm indoor location shortly after sunset.
• Tell students they will have the chance to learn more about what is in the night sky
• Ask students to think of night-sky objects they know (planets, moons, constellations, stars, galaxies) and if they move
• Discuss distances to each type of object, and which might appear to move in the sky
• Do a demo with one student as earth, another as sun, and others as other objects. Simulate the motion of each, and the relative view of the sky from the earth.
• Introduce planispheres as a tool to help us predict what will be in the sky at a given date (angle of solar orbit) and hour (angle of planetary rotation)

EXPLORATION

• Hand each student a planisphere
• Ask students to rotate dials so that the top and bottom flaps align somewhere for today's date and time. Note that the night sky we see now is the same as seen on other dates/times that are also currently lined up.
• Let students see that a portion of all the night sky is visible at this time, and that it rotates as the date/time change. See also that one point, the north star, never moves, because it is always 'up' (recall the demo in the introduction).
• How can we orient ourselves? We need to orient relative to north. Where is that? Inside, point it out, but note that the right side of the Big Dipper points to the north star.
• Have students hold the planisphere flat in front of them. Stand so that the bottom of the planisphere (the part closest to the student) says north, and the student is facing north. Constellations should then be visible overhead in the relevant section of the sky, and easily located.
• Ask if objects rise in the east or west? Ask students to think about how the earth rotates, or try using their planispheres to answer the question (by rotating the dials).
• Ask if the Milky Way galaxy moves. Use the planispheres and logic to find out.
• For older groups: identify circumpolar constellations that never set at this latitude. Also, ask why the planets and moon are not shown on the planisphere. Show the ecliptic plane they are all found in.
• Ask each student to find one object or constellation they want to see with the planisphere.

APPLICATION

• Distribute warm blankets if needed
• Move group outside and have students find north with the Big Dipper (use the laser pointer if needed).
• Orient planispheres and have each student find their object with the help of a partner. (Then switch objects within each pair - group).
• Use the laser to point out other interesting night sky objects (transiting satellites, planets, galaxies, Milky Way)

* Take 5 minutes of silence to let eyes adjust to darkness. Have students try to count stars in some region of the sky, or see if they notice stars of different colors, binary stars, etc.

ASSESSMENT

• Determine if students successfully found their constellation
• Move inside

RESOURCES

• How to use a planisphere [1]
• How to find Andromeda galaxy [2]