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Paper Plate Education
"Serving the Universe on a Paper Plate"

Activity: Defining the Zodiac

Norcia_plate_pixR.gif (75205 bytes) Norcia_plate_zoomR.jpg (20698 bytes)
Plate courtesy of Gary Norcia.

The following text is excerpted from GLPA Proceedings, 1992, pp. 82-83; used with permission:

Objective:  Make a paper plate model of the ecliptic the student can use to find constellations in the sky.

Materials:         1 paper plate per student


                        protractor (if you want accuracy)

Assessment:  Have the students describe in an observing journal how they have used the tool.

Background:  All objects in the Universe are in motion.  The Earth goes around the Sun once each year (defining the year).  But we don't feel this motion.  To us riding on the moving Earth it appears the Sun moves in front of the background of distant stars.  To teach this basic concept, use a light in the center of a room.  Place constellations (names or outlines on paper) around the room.  Have the student walk around the light (Sun) and name the constellation in line with the Sun.  You can define the season by the constellation, but the position is not the cause of the season. 

Lesson:  "Out of the 88 constellations in the sky, 12 are more well-known than the others.  We will make a paper plate tool to help you find these 12 constellations.  Fold your plates into fourths, then unfold them.  This marks the center where we will locate the Sun.  It also makes four marks along the edges.  This is a "celestial" tool (see previous activity), so we will mark one of the four folds at the edge as '0'.  Then going left from '0' will be '180 degrees', next is '270 degrees', and last we mark '360' at the same location as '0'."

"Now we need to locate some points along the edge of the plate where the Sun would appear to cross from one constellation to the next.  This is like driving across the state.  You cross county boundaries, but it still looks the same.  You would have to know the sky real well to find the exact boundaries, but they are on star maps."

Following is a table of information.  Use the part your age level of students will understand.  For younger students, divide the plate edge into 12 for the months of the year (fold into 4th, then into 3rds.  Start January on a fold line but not the '0' line in degrees is also the 1st day of Spring for us in the northern hemisphere... and that is just past mid-March).  You might have them count 'crinkles' along the edge.  The plates I use have 1 'crinkle' for each 6.5 degrees.  If students have protractors, use degrees.  I have given the degrees broken down into arc minutes.  It's hard to be that accurate, but it teaches to concept of a portion of a degree.  If students have learned about right ascension (like longitude lines in the sky), use the hour, minute, second figures under R. A..

Degrees            R. A.                         Sun moves into Constellation

000o  00'       00:00:00                  Vernal Equinox in Pisces, 1st of Spring!

028o  42'       01:46:40                  Aries

053o  21'       03:24:05                  Taurus

090o  09'       06:00:35                  Gemini

118o  00'       08:00:15                  Cancer

138o  03'       09:22:00                  Leo

173o  51'       11:37:30                  Virgo

180o  00'       12:00:00                  1st of Autumn!

217o  48'       14:21:45                  Libra

241o  00'       15:55:30                  Scorpius

247o  45'       16:23:30                  Ophiuchus (OFF ih YOU cuss)

266o  12'       17:43:35                  Sagittarius

299o  39'       20:07:20                  Capricornus

327o  30'       21:58:40                  Aquarius

351o  37'       23:29:00                  Pisces

Note:  From Uranometria Epoch 2000.  Students will know most names except Ophiuchus.  To make a plate showing the Signs of the Zodiac as in Astrology, divide the edge into 30 degree even segments, start with Aries and leave out Ophiuchus.  They used 12 instead of 13 due to 13 being unlucky.  Most people are off one sign due to the changing of the earth's axis in the past 3,000 to 4,000 years...called precession.  The same reason why Polaris hasn't always been the pole star, and won't be again for 26,000 years.  During the time Astrology was used, people thought all objects in the sky were just above the clouds.  They could not imagine the great distances to the stars.  They also thought all stars were on a sphere the same distance away.  Many stars making up a constellation are at vastly different distances.  Stars are moving at various directions, some time far into the future, the patterns will look different than they do today.

"To use your paper plate tool, you will need to learn what one of these constellations looks like.  Many people want to know the one the Sun appears to be in front of on their birthday.  Think about that a moment.  If the Sun is in front of the stars of Capricornus, would that be a good time to study the constellation?  No!  You can't see that group of stars because the sun's light would make it daytime.  I think it is neat to pick the constellation opposite the sun on my birthday.  On my birthday it would rise when the sun sets, be overhead at mid-night, and I can study it all night if I could stay up!  It is also fun to look at it and think how the sun will be in front of these stars in six months from now."

"Once you can find one of the constellations, stand facing south, hold your plate so the constellation on the edge of the plate is closest to the one in the sky, and the plate will show you what is on either side.  As you learn the constellation patterns, you might draw them on the paper plate tool just below their name to help you spot them in the sky.  H. A. Rey is the author of a book called THE STARS.  I find his patterns easiest to learn.  Most schools have a copy."

Note:  Ben Mayer is the author of a book ASTROWATCH.  This book has excellent photos of the constellations of the ecliptic.  It was published by Putnam, NY in 1988.

Final note:  By definition, the ecliptic is the apparent pathway of the sun caused by the Earth going around the Sun.  See Astronomy Lesson #8 for more on this important pathway.

Contributed by Wayne James.


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