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

Paper Plate Astronomy Video Narration 

Below is the narration that accompanies the respective activities on the Paper Plate Education videotape.

INTRODUCTION

Since the 15th Century, round paper instruments called volvelles have supported the teaching of astronomy. The inclusion of volvelles in Peter Apianus’ ambitious 1524 undertaking, Cosmographia, helping to propel the book to the 16th Century  equivalent of a bestseller, being printed in at least forty five editions in 4 languages.  

Paper plates were used to inspire creative thinking as early as the 1950s when they allegedly inspired the blunt body design of the Mercury spacecraft.

Since 1992, members of the Great Lakes Planetarium Association have developed a collection of paper plate activities that reduce complex notions to simple paper plate explanations.

Dozens of inexpensive activities that support lessons in multiple disciplines for all ages are available at the Paper Plate Education website.

This video will demonstrate the construction and use of nine hands-on activities, mostly for advanced students but adaptable to all ages.  These activities are interactive, they are inexpensive, they are instructional, and they fun.  So here is what we are serving on paper plates.  Enjoy.

 LIST OF ACTIVITIES

...We will begin with Sunrise Sunset.

With this activity, you draw a local horizon around the perimeter of a plate.   Over several months, track the changing position of the sunrise or sunset against the local background.

With the Satellite Tracking Bowl you plot the predicted passes of satellites onto a bowl which you can take outside as a viewing aid.

The Sub-Solar Cup indicates   in real time   the position on the earth at which an observer can see the sun directly overhead.  This allows the user to track the changing position of the sun between the tropics and to trace out and define the analemma, that figure-8 shaped feature seen on some globes.

The Altitude Measurer is an astrolabe-like device that allows you to measure   in degrees   the altitude of celestial objects up from the horizon.

The Platisphere is a device that reduces the sphere of stars to a paper plate.  With this tool you can accurately determine the positions of the circumpolar stars for any given time and any given date.  This video shows several variations of the Platisphere, including a children’s version, a tactile version for visually impaired users, and the Photographic Plate, which predicts the smear of stars   or star trails    produced from a long duration exposure on film.

The Latitude by Polaris plate illustrates how navigators used the North Star to determine their position, correlating the observed altitude of Polaris with the person’s latitude.

The Altitude of the Noon Sun plate demonstrates the range of the sun’s altitude through the seasons for any given location.  It also conveys why the sun sometimes never rises in the far north for months at a time.

With the Moon Finder you observe and plot the moon’s phases and its position relative to the sun.  Then you make a model which can predict the position of any given moon phase for any date and any time.

Lastly, with the Paper Plate Planet Pointer, you plot the position of the planets in orbit around the sun and make a device to transfer that model to the real night sky.  Essentially,  your device shows you where to look to see the planets.      So let’s begin...

 INDIVIDUAL ACTIVITY DESCRIPTIONS

 Sunrise Sunset

Have you ever noticed when driving how the sun rises or sets to the side of an east-west road, but near the equinoxes it appears directly in your path? Here you will observe and record the changing position of the sun at sunrise and sunset through the seasons.

(doll grabbed and backyard pan)  Imagining yourself to be at the center of the plate, you will mark the changing position of the sun against local landmarks.

(doll lowered) Around the perimeter of the plate label the cardinal directions and draw familiar features:  trees, houses, a flagpole...  Then observe the sun for several months as it moves northward from its winter position ... through east... until it “stands still” at its summer solstice limit....    Then the sun will appear to turn around and head back south along the horizon to its winter solstice extreme.

In this farm scene example, the sun rises left (or north) of the silos in the summer...  between the silos at the equinoxes...   and right (or south) of the silos in the winter.

 

Satellite Tracking Bowl

With the Satellite Tracking Bowl you plot the predicted path of visible satellites on the inside dome of a bowl.  Then you use the bowl as an alignment tool to face the direction and anticipate the path of the satellite crossing overhead.

Conveniently, foam bowls such as Hefty brand have 36 decorative scallops around their perimeters, so each scallop represents 10 degrees.  You can calibrate your horizon into 360 degrees of azimuth...  or you can label the cardinal points --North, South, East, and West-- and draw features of your local horizon similar to the Sunrise Sunset activity.  Notice here we have on the near edge the zero degree mark for North and on the opposite side is South.

One bowl you will cut in half to make a tool for plotting the satellite’s positions onto a second bowl, which is the end product.

Envision yourself standing under this bowl or dome of stars overhead.  You want to mark the angular amount from the horizon (or zero degrees) up to your zenith, overhead at 90 degrees...    Hold a protractor against the edge of the halved bowl and mark zero-to 90 degrees near that edge...

Then label those hash marks zero through 90 degrees.

Obtain satellite data for your location from the “Heavens Above” website...  It lists satellite name, when the satellite pass starts, maximum altitude, and when satellite visibility ends.

Here’s an example of how you will plot the satellite position.  Place the half-bowl inside the whole one and rotate it so that the zero-degree mark is near the desired azimuth, or compass heading.  Then go up to the desired altitude and mark that spot on the bottom bowl.

From this evening’s predictions we see the object named Meteor 1-29 Rocket, magnitude 2.5, is first seen at this time, 10 degrees of altitude in the south southeast.

(finger on bowl edge)  Here’s the southeast ... so this is south southeast...place the bowl there...and make a mark at 10 degrees.

Next, this satellite reaches a maximum altitude of 88 degrees toward the north northeast, which is essentially overhead.

You can plot this...here’s NNE..88 degrees.

The satellite pass ends at 10 degrees in the north northwest...which you again plot.  Notice how sometimes the full duration of the satellite pass can not be seen due to obstructions nearby.

Draw a line connecting these points...

and label the path with satellite name and starting time when the satellite first appears...When you are done you have an entire evening’s worth of predicted passes represented visually on the bowl.

To use it, you hold the bowl overhead, align yourself in the proper direction, and look near the predicted spot in the sky....  

 

Sub-Solar Cup

With the Sub-Solar Cup you position yourself on top of a globe.  Cross-hairs on the cup indicate the location on the earth (called the sub-solar point) where the sun would be found directly overhead at that moment.

Using an opaque plastic cup, on the bottom, dead center, drill a small hole.  On the side, cut out a large viewing port, and on the front affix these crosshairs, again so they cross dead center. 

On a sunny day, align your globe north and south.  Your meridian and the globe’s lines of longitude should be parallel.  Concurrently position it so your location is on the top of the globe.  In this example we are filming from Cleveland, Ohio, so a figure placed on Cleveland would be upright.  To help align the globe accurately, place a bubble level on top--in this case, Cleveland--and adjust it, still keeping the globe aligned north and south. 

To use the cup you hold it over the globe so that the circle of sunlight is centered on the crosshairs...  Here, on a mid-March morning, you see the sub-solar point just of the coast of Brazil, near the mouth of the Amazon River.

Later in the morning you can see how the path of the sun has shifted westward into the interior of Brazil.  This introduces other lessons in geography.

Later this mid-March afternoon, you see the sun has moved over the Pacific Ocean, but still just below the equator.

...So while you can record the sun’s changing position from day to day, you can also record its changing position from week to week, through the seasons.  Here, after the vernal equinox, you find that the sun has moved north of the equator.

As a variation, you can use a simple piece of pipe with crosshairs.  Imagine it to be a water well, and simulate the work of  Eratosthenes, who used the observation that a well located on the Tropic of Cancer reflected the sun on the summer solstice-- the well cast no shadow.  This well   defined the northern limit of the sun’s path and led Eratosthenes to determine the circumference of the earth.

 

Altitude Measurer

For this activity we will make an astrolabe-like device for measuring (in degrees) the altitude of  celestial objects up from the horizon.

Using a foam plate with 36 scallops around the perimeter, mark and label ten degree increments from zero through 90.  From the 90, draw a line across the diameter of the plate.

Place a straight edge along the diameter and draw another line parallel to and above the diameter.

As shown here, on the flat part of the plate in from each edge draw two perpendicular lines between the horizontal lines.

Neatly cut across the plate along the upper line.

Then cut in along the diameter as far as the short line you just drew... And repeat that on the other side.  

Score the perpendicular line from the horizon up to the top edge...and bend the tab back one way.

Repeat that on the BACK side of the other edged of the plate and bend that tab back the opposite way.

For clarity we put red lines along the top of our viewing sights.  From the center of the plate, midway along the diameter line, suspend a weight from string.

When using the altitude measurer to sight a star, the plate can not appear open.   Rather, the sides of the plate are unseen and the two gun sights should be side by side.   If the near gunsight is lower, then you are aiming too high; if the distant gunsight is lower, then you are aiming too low.  They should align together with the target visible along the edge of the plate  [HOLD FRAME]  Though the targeted celestial object shown here looks like the sun, you must never use this device to view the sun directly.  Eye damage can result.

...Have a partner read the angular measurement off the front of the plate.

 

Platisphere   

A plaNisphere is a device that reduces the sphere of stars to a plane surface.  Around the perimeter you find dates and times for setting the dial.   In this activity we will make a 6Platisphere, which reduces the circumpolar stars to a paper plate.  With this device, you can determine the position of the circumpolar constellations for any given time or date as they rotate around Polaris.

When you are facing north, as the hours pass you see the stars move starwise,  or counterclockwise.  If you denote due north with a red meridian line, you see the pivot point around which they rotate is Polaris, the north star.

Use astronomy software to make a star chart.  While centered on Polaris, set the sky to January 1 at midnight.  Make the field of view equal to 50 degrees.  And if you live with light pollution, set the limiting magnitude to 3.5. 

In addition to the red meridian  enable the constellation outlines and the equatorial grid.

Then print the star chart.

Here is the red meridian line.  Polaris is at 90--then there are 80, 70, 60, 50, and 40 degrees of declination.--cut out along the 40 degree circle of declination, being sure to include the major stars Capella, Vega, and Deneb.

Center and affix the star chart on a stack of 9-inch black plates.  We will use the following technique to mass produce plates for a group.

On an area where there are few stars, put a clamp over an entire stack of plates.

At a drill press or with a hand drill you will use three different-sized drill bits. 

Use the smallest bit to drill through the fainter stars and a slightly larger bit to drill through the brighter stars, as indicated on the star chart.  The Platisphere really works well when you limit the number of constellations depicted.  You can always add them later as your observing progresses.   Also, if you are in light polluted skies, omit the four fainter stars in the middle part of the Little Dipper.  It is recommended that you do include the three bright guide stars, even if the printed chart shows them to be below the horizon at the moment.

Of course, use caution with the drill near your fingers.

With a large bit in the drill, move up along the north meridian line and drill a hole at the top of the plates near the edge.  This will be your indicator hole.

When you remove the star chart you have a stack of black starfield plates remaining.  Here is the Big Dipper.. which leads you to Polaris...and beyond to the W of Cassiopiea....Down low are Deneb...Vega...and Capella.

Now, to make a horizon for your latitude, cut off the the semi-transparent horizon from the bottom of the printed star chart...Center the truncated star chart on a larger 10-inch white plate and draw a line (woops) onto the white plate as shown. 

Add a few horizon features--a house, a tree--and cut off the rest of the plate above that.

To make individual horizons, put this horizon template on a plate, trace out the horizon line, and cut.  To mass produce horizons, copy the template onto a stack of white 10-inch plates and cut the whole stack at a band saw or scroll saw.

You now have a black starfield plate, a 10-inch background plate with a small hole in its center, and a cut out horizon.  Turn the horizon upside down and staple it to the big white plate, giving it a 3-D appearance. 

Slip the black one inside and secure them with a paper fastener.  With the large indicator hole on top--set for January 1 at midnight-- you’re Platisphere is ready for use.

Beginning at January 1, every day the stars shift about 1 degree “starwise” or counterclockwise...until after one year, or just over 360 days, the stars have shifted through 360 degrees...hence,  the 1 degree per day.

From January 1 we can subdivide the plate into 12 months--February 1, March 1, April 1, May 1...

October 1 November 1, December 1, and back to January 1--all being at midnight.

Concurrently, every 24 hours the stars will rotate about once around...so half a plate is 12 hours, a quarter plate is 6 hours...If we start on January 1 at midnight, a quarter turn takes us to 6 a.m., then noon, then here you see the hole on the right edge at 6 pm (again, all for January 1) and finally by midnight the hole has returned to about its starting point.

So let’s try an example--set the sky for April 1 at 9 pm. 

From January 1 at midnight, move forward 3 months...to February 1, March 1,  and April 1 at midnight.  Then set the time, moving forward 21 hours from midnight--to noon, this is 6 p.m., plus three more hours to 9 p.m....So we’ll move the indicator hole from the April 1-midnight position ... forward 21 hours to April 1 at 9 p.m.  So this how the stars will appear when facing north on April 1 at 9 p.m.

Another way to get to April 1 at 9 p.m....From April 1 at midnight you could go forward 21 hours...or, from April 1 at midnight go backwards in time by  3 hours to 9 p.m.  So again this is how the north circumpolar stars appear on April 1 at 9 p.m.

In this second example you’ll see how two different times and dates can have the same starfield.  From January 1 at midnight, move “starwise” until the indicator hole is on the right edge, or at October 1-midnight. 

From here you can move it forward either 2 hours or one month.  This could be either October 1 at 2 a.m. or November 1 at midnight--same starfield, two different circumstances.

Notice how at these two opportunities the Big Dipper may be hard to find simply because it is low on the horizon and near obstructions.  And since the end star of the Big Dipper, called Alkaid, dips below the horizon from this latitude, it is technically not a circumpolar star.

Plastic Platisphere

Real quick here... to make a Platisphere that holds up in the weather--and has been field tested in the hot tub--make it out of two plastic plates.  They fit snugly together and the ridges help lock them together as well.

 

Platisphere for Children

You can modify the Platisphere to simplify its use for children and adults alike.  Instead of setting it for the exact time and date, you set it simply to a sketch of the current season and assume it is for evening use only.

We’ll use the same starfield plates.  From January 1 at midnight, back the starfield up several hours so this area next to Cassiopiea is upright--January 1 in the evening.

Cut out a viewing window in that area.

On the white background plate, draw figures to represent the four seasons.  From winter on top move “starwise” to spring, summer, and fall.--be sure to draw them upright.

Then place the black starfield on top and secure with a paper fastener.

In the winter evening, the Big Dipper stands on its handle.  In the spring, the Dipper is high overhead, as it is in the Summer.  In the fall the Big Dipper is low.  And by winter it returns to standing on its handle.

 

Tactile Platisphere

The Platisphere can also be modified as a tool for visually impaired students, as the following demonstration suggests.

To make it, cut out the starfield from a black plate and invert it.  Center the upside down template on a red plate and drill your holes downward.  Because the constellations appear backwards on the front of this plate, we use the red plate so as not to confuse it with the regular Platispheres.... 

It’s been found that the back sides of the the drill holes are more easily discerned by fingers.

 

Photographic Plate

If you take a long duration picture of the circumpolar stars, it produces a smear of stars called star trails. You can use the Platisphere to make a  Photographic Plate, which predicts the star trails for an exposure of any given duration.  In this example you can simulate the view of the heavens on the opening hours of the new Millennium.

Divide a 10-inch white plate into 24 hours.  

For our [sample/millennium] photograph we will take a 3-hour exposure.  Set the Platisphere to the starting time.  Place a pen in the hole of a star and swing an arc through the three hours.  Then back up to the starting point and do it again with the next star.  Repeat this for every star hole.

When you are done, remove the starfield plate to reveal the photographic plate.  [And this is how the new millennium really began.]

 

Latitude by Polaris

Here we will show how a navigator determines her latitude from the altitude of Polaris, the North Star.  As our navigator’s ship travels from the equator, the altitude of Polaris above her horizon not only increases, but is congruent with her latitude.  By the time she reaches 90 degrees of latitude, the altitude of Polaris is likewise 90 degrees.

Draw a circle to represent the earth on 10-inch white plate.  ..Extend the equator out to the edge.  and extend the north pole out to the edge, too. .. Label these the equator, celestial equator or C.E. , north, and Polaris at the north celestial pole.

Polaris is so far away that its starlight is coming in parallel to the north celestial pole.  Draw several parallel lines to reinforce this notion.  Looking up any one of these lines of sight, no matter where you are on the earth will end on the north star.

Use a protractor and label the latitude, shown here in increments of 15 degrees.

From about this part of the earth...to about here, cut a slit along the perimeter of the earth.

Mark a 3 by 5 card as shown... Draw some water with a ship on it... [This is the direction our navigator would look toward the horizon, so ] label the red arrow “To Horizon”.  This the direction to our navigator’s horizon, up from which she measures the altitude of the stars.

Slip the card under the slit on the plate so the waterline is on the edge of the earth.  With the vertical line visible at the earth’s center, mark the card.

Cut out around the ship and punch out the two holes, as shown.

On a second 3 by 5 card, draw a red arrow and label it North.  Swing an arc...punch a hole... and cut it out as shown.

Fasten the arrow cutout to the ship cutout at the 90 degree bend. 

And then affix the hole rig to the plate.

Using the Latitude by Polaris

If our ship begins a journey north at the equator, the navigator looks this way to see starlight from Polaris coming in tangent to the equator.  From the perspective of the ship, the direction the North Star is straight ahead toward the northern horizon.  The altitude of Polaris is zero degrees.

As it travels north, the angle between the horizon and Polaris, the altitude, is 30 degrees.  At the same time, the angle from the equator to the ship’s position, the latitude, is also 30 degrees. 

The ship moves north.  When the altitude of Polaris is 45 degrees, the ship’s latitude...is also 45 degrees. 

By the time the ship reaches the north pole, the pole star is directly overhead --altitude equals 90 degrees.  At the pole, the latitude is 90 degrees.

For a different perspective you can focus in on the ship to see the angular height of Polaris rising congruent with angle of  latitude.

 

Altitude of the Noon Sun

With this dial you set the north star to any latitude.  You can then observe the range of the noon sun’s altitude through the seasons at that location.

Begin by drawing lines radiating outward from the center of a plate.  Cut a wedge from another foam plate to expedite the process.  Using foam plates with 36 scallops allows us to make 10 degree increments. 

You will place a house at the center of the plate later, with the line across the diameter representing the horizon.   To the left is the northern horizon, to the right is the southern horizon.  Label the plate 180 from horizon to horizon--plus 30 degrees below each horizon--as follows:

Start on the right edge and label upward from zero degrees...to 90 degrees.  After 90, start decreasing back down to zero degrees.

Then from the zero-degree marks on both edges, label zero to 30 degrees below the plate’s diameter.

Draw a house at the center and cut out a slit along the ground and over the house as shown.

On a second plate you want to make a diagram similar to this.  With the earth at the center, you will project lines outward and label them accordingly.  Then you plot the sun’s position above and below the celestial equator for the 21st day of each month.  This angular measurement from the equator is called declination, and it varies through the seasons.

Draw a circle on a paper plate, and then place it on your foam plate.  From the center of the earth draw and label lines--equator, north pole    with the north star above it.

If you extend the earth’s equator outward it denotes the celestial equator.  A line out to 23 1/2 degrees defines both the terrestrial and celestial Tropic of Cancer to the north and Tropic of Capricorn to the south.

On the flat part of your plate, mark the position of the sun above and below the equator for the 21st day of every month.  Notice how after June 21st the sun’s July 21st position essentially coincides with its May 21st position.  Same for the pairs April and August, March and September (the equinoxes), February and October, January and November... and then the sun bottoms out on December 21st, the solstice at 23 1/2 degrees .. 

Drawing a line out through the the June and December extremes again defines the tropics, which you can label.

Cut off the crinkled edge of the plate, preserving your monthly suns.

Slide this under your horizon plate...and secure them with a paper fastener.  Your device is ready.

 

Using the Altitude of Noon Sun

From the previous activity you learned that the altitude of Polaris above the horizon coincides with your latitude.  So set the north star to point to your latitude.  If, for example, your latitude is 40 degrees, set the north star line to 40 degrees.

Then here would be the northern limit at the June solstice, and here the southern limit at the December solstice, of the noon sun for that latitude.

If you shift to a lower latitude you can see how much higher the sun is through the seasons.

Going to the latitude of the Arctic Circle, notice how the noon sun just touches the southern horizon on the December solstice. 

And going further, to the north pole, you can see how the noon sun remains below the horizon for six full months between the September equinox and the March equinox.

 

Moon Finder

With the Moon Finder you first observe and record the moon’s phases and its position relative to the sun.  Then you make a model which can predict the position of a given moon phase for any date and any time.

Volvelles are paper instruments that were often included in books.  Here you see a 16th century volvelle set to a waning crescent moon with the sun to its left.  Your Moon Finder will be able to perform similar functions as that historic device.

Envision a person facing south with her back to you.  East is to her left; west is to her right.  The noon sun is seen high in the south, and then sets toward the western horizon.  At sunset it disappears below the horizon, but if the earth were transparent, after sunset it would be below the horizon.

Using a paper plate, the setting sun looks like this...

Make a horizon plate as shown... and cut out the outer rim and the inner window.

Draw a person with her back to you, facing south.  Again, east to toward the left horizon, west is toward the right horizon.  Color in some hair to reinforce that you and the figure are both facing south.

The sun will serve as a time indicator--a timepiece of sorts.  But refrain from calling it a clock--that only confuses people.  In 24 hours it appears to rotate around the observer once.  At sunrise the sun is easterly; at noon it is high in the south; at sunset it is westerly; and opposite of noon is midnight.

Adding labels, when the sun is here the time is PM...down here opposite the noon sun is midnight...and when the sun is here it is AM.

First you want to observe the sun over time to see how far from the sun in degrees and in which direction the respective moon phases are seen.

For example, one day from the afternoon sun  you may see the first quarter moon 90 degrees to the east.

In the morning two weeks later, the last quarter moon may be seen 90 degrees west of the sun, so record it there.  Repeat these observations until you have most of the moon phases plotted on your plate.

From a God’s-eye view above the earth, with the sun shown off the plate in the distance, the half of the earth opposite the sun would be in shadows.  So darken in the night side of the earth

Again, viewing from above the earth’s north pole, the moon will orbit this way around the earth.  The sunlight comes in from this direction, so when the moon is here, we color in the dark side of the moon and label it.   This starting phase, where the moon is between the earth and the sun, is called New Moon.  We’ll bring the sun onto the plate, but imagine it at a vast distance. 

The moon then orbits this way 90 degrees.  Color in the dark side, and label it First Quarter.  The moon has travelled one quarter of its orbit around the earth.

Continue...    when the sun and the moon are 180 degrees opposite...we have a full moon.

After three fourths of its orbit the moon reaches the Third Quarter, or Last Quarter, phase.

Next, correlate the names of the phases with their respective appearances as seen from earth.  Use an old calendar that depicts the phases.

In the New Moon position, affix a dark moon to show how it appears--or rather, not be seen-- from earth.

Between New Moon and First Quarter is a thin crescent moon with its cusps pointing away from the sun. 

Next is the First Quarter, shaped like a “D.”

Between First Quarter and Full is a waxing gibbous moon.

And then the fully illuminated Full Moon.

The moon begins waning, with this gibbous moon.

And at Last Quarter the moon looks like a bright letter “C”.

Finish with a thin, waning crescent, again with the cusps pointing away from the sun.

 

When using the Moon Finder, concentrate on only one phase at a time and on the sun.  For clarity we put a red dot by the moon phase of interest.  Ignore the other moon for now.... 

 It is important to remember that the angular relationship between the sun, the earth, and the moon remains the same, regardless of whether it seen from above--the God’s-eye view--or from the earth-bound perspective.  The angle remains the same. 

In Example 1, the First Quarter moon will always be 90 degrees east of the sun.  When the sun is toward the west, this moon will be 90 degrees away in the south.

The First Quarter moon sets around midnight, as indicated by the sun’s position.

And it isn’t seen again until it appears toward  the east at noon.

The Full Moon is always opposite the sun, 180 degrees apart.  The full moon rises when the sun sets.

Just as you guess the hour of the day from the sun’s position, you can estimate the hour of the night by the Full Moon’s position.

...

Note that these times are only approximate, especially away from the equinoxes.  You may have to find the current day’s sunrise and sunset times and interpolate between them.

If you wish, you can embellish your Moon Finder with these items... The moon is waxing between New and Full, and then waning between Full and New.

A crescent is seen from Last Quarter to New Moon, and from New Moon to First Quarter.

Gibbous extends from First Quarter to Full and from Full to Last Quarter.

When you are done, compare this model with your observations plate that you made earlier.

 

Planet Pointer

Sometimes after the sun sets below the horizon, you can see planets in the western sky.

This volvelle was used in the 16th (?) Century to track the planets.  In this activity you will plot the planets in their current positions, then overlay a local horizon.  The resulting dial suggests where to look for the visible planets.

First make a horizon plate.  Draw a line across the diameter...and a person facing south, with east to her left and west to her right.  Then cut out this outer fringe.

On a second plate, mark a blue earth at the center of a plate.  20 millimeters away make a sun symbol...and sweep an arc from the sun through the earth... Then draw this line outward from the earth through the sun to the edge of the plate.  A person on earth would look in this direction to see the sun.

From the sun, sweep arcs for the other visible planets

Using foam plates that have 36 scallops, mark 24 hours of Right Ascension counterclockwise on a foam  plate.  One hour equals 1 1/2 scallops.

Place your planet orbits plate on top and align the sun with its current right ascension--in this case,  7 hours and 40 minutes.  Planet data can be obtained from astronomy-related magazines or from the Heavens Above website.

From earth-- not the sun-- plot the positions of the planets...  Notice how for Mercury and Venus the planets could be located in one of two spots, close in their orbit or far away.  What matters for us is simply the angular direction relative to the sun.

From earth we would see Venus in this direction against the background stars.

Also notice how the inferior planets are seen relatively close to the sun.

An alternative to using right ascension  is to duplicate a schematic of the planets in orbit around the sun, again, this being from the Heavens Above website.  Place the planets in their approximate positions and draw lines outward from earth through the planet to the plate edge.

...

From earth, here is the sun in this direction... Mercury is nearby to the right, or west... Venus to the left...

And add labels...

Affix the horizon plate with a paper fastener and your instrument is ready.

 In this example, we set our sun to below the horizon.  Low in the west you can then see Venus,  with Mars setting shortly thereafter.

As midnight approaches... Saturn rises in the east, followed shortly thereafter by Jupiter to its left, or east.   By daybreak the two giant planets are high toward the south southeast, with Mercury probably lost in the glare of the sun.

 Visit the PPE website at ....for dozens more engaging activities, including these…

Contributed by Chuck Bueter

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