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Introduction


A Star Wheel is a circular map of the stars. At any given time it can show what stars are in the sky and where to find them.

Another word for Star Wheel is planisphere.

A Star Wheel is an ideal tool for the beginner stargazer. It not only points the way to the stars, but it helps you understand the mechanics of the night sky.

The Astronomy In Your Hands Star Wheel is made from paper. You download, print, cut out and assemble it using no more than scissors, sellotape or scotch tape, and in some cases a glue stick.

Features

  Made from paper and designed to be photocopied

  • Produce a class set at next to no cost
  • Take it hiking and treat it as disposable

  Uncomplicated

  • Appeals to children and adults alike

  Universal

  • Wherever you live, you can have a Star Wheel specific to that place, showing star positions accurate to within 5°.
  • Travellers can make up a set covering an entire world trip, or just the parts they intend to visit.

  Two levels of detail

  • The City version shows only the major stars and constellations, giving it a clear, unintimidating look. It also shows constellations in their true shapes, avoiding the distortions of traditional planispheres.
  • The Milky Way version shows the Milky Way in unprecedented clarity and includes over 2,000 stars on each side of the wheel.

  Bilingual

  • The Māori /English version for Aotearoa/New Zealand is the most comprehensive Māori star chart ever published.

Preview

A Star Wheel has two parts – a pocket and a wheel. The wheel goes in the pocket, and the pocket has a window in it through which you can see the stars. The wheel turns to show different stars at different times. The animation on the right shows a wheel being put into a pocket and turned. There are photographs of star wheels in Activity 3 – Make a Star Wheel.

Pocket

Here is a selection of pockets, showing the front window only.

Pocket Latitude 0

Equator
Double-sided

25° Latitude  
Double-sided  

Pocket Latitude 25
Pocket Latitude 55

55° Latitude
Single-sided

Click the images for larger views.

Note how the shape of the window changes with latitude. Also note that some of the pockets are double-sided. The double-sided pockets have front and back windows. We have only shown the front windows here. The back window is used to see the parts of the sky that you cannot see in the front window.

Wheel

The wheel comes in two levels of detail: City wheel and Milky Way wheel. Both the City and Milky Way wheels work in the same pocket. The wheels are 9.8 inches (250mm) in diameter.

City Wheel

The City wheel is designed for beginners. It contains only the most recognisable stars and constellations, ones that you can usually see from a medium sized city with reasonably clear air. These images are details from the centre of the Northern and Southern Hemisphere City wheels.
City Wheel Northern Hemisphere - DetailCity Wheel Southern Hemisphere - Detail
Click the images for a larger view of the wheel. Note that these images are fuzzy due to the limitations of web graphics – the downloadable files print as sharply as your printer is capable.

Milky Way Wheel

The Milky Way wheel is designed to show all the stars you might see from a rural location as well as the full splendour of the Milky Way in . These images are details from the centre of the Northern and Southern Hemisphere Milky Way wheels.
Milky Way Wheel Northern Hemisphere - DetailMilky Way Wheel Southern Hemisphere - Detail
Click the images for a larger view of the wheel. Note that these images are fuzzy due to the limitations of web graphics – the downloadable files print as sharply as your printer is capable.
Star Wheel Loading Animation

Bilingual

The Māori /English version of our Star Wheel is available for Aotearoa/New Zealand. The Māori names that are used in this version have been compiled from previously published names. A full list of sources is given in Māori and Constellation Names.

This image shows details from the centre of the Māori /English version of our Star Wheel.
Bilingual Wheel - Detail
Click the image for a larger view of the wheel. Note that this image is fuzzy due to the limitations of web graphics – the downloadable files print as sharply as your printer is capable.

We are able to prepare Bilingual Star Wheels for other languages. Your enquiry is welcomed.

Download and Assembly

The Astronomy In Your Hands Star Wheel is available for download to subscribers only.

The Star Wheel downloads page automatically selects the correct version depending on your location. Full instructions are found in Activity 3 – Make a Star Wheel.

Travel Kits

A travel kit is a set of wheels and pockets that together cover an extensive area of the globe.

Wheels: There is a different wheel for each hemisphere. The stars are the same, but the date markings are different in different hemispheres. If you stay in one hemisphere, you only need one wheel. If you cross the equator you need two wheels.

Pockets: There is a different pocket for each 10° of latitude. You will need one pocket for each latitude band that you visit. Ten pockets will cover almost the entire world.

To build a travel kit, identify the latitudes you will visit. A good world map, or an atlas, is probably the best way to do this. You can also find the appropriate latitudes by looking up the main places you will visit at one of:
  1. our Wheels and Pockets downloads page
  2. the Mirapla Sky for Windows settings dialog box
  3. the Heavens Above web site

Having identified the latitudes you will visit, download the necessary pockets and wheels according to this table:

For latitudes

Use the pocket for

And the wheel for

50 N to 60 N

London, UK

Los Angeles, California

40 N to 50 N

New York, NY

30 N to 40 N

Los Angeles, California

20 N to 30 N

Miami, Florida

10 N to 20 N

Manila, Philipines

10 N to 10 S

Quito, Equador

10 S to 20 S

Cairns, Australia

Sydney, Australia

20 S to 30 S

Brisbane, Australia

30 S to 40 S

Sydney, Australia

40 S to 50 S

Hobart, Australia

When you have both Northern Hemisphere and Southern Hemisphere Star Wheels, be very careful to get the correct wheel in the pocket. The wheels are labelled with their hemisphere in the outer ring on the back. Check before you go outside – it’s quite easy to get the wheels mixed up and very confusing if you do. Note that the 10° N to 10° S pocket uses the Northern Hemisphere wheel.

Science Background Knowledge

What Shape is the Sky?

When you look at the blue sky during the day, what shape do you see? Our eyes cannot tell how far away the sky is, so our brains decide that it is all the same distance. This makes it look like the inside of a dome, ball or sphere.

When you look at the sky on a clear night, what shape do you see? Although the stars are all different distances away, our eyes cannot tell this. They all look the same distance to us. So the night sky looks like the inside of a dome, ball or sphere.

There are stars in all directions from the Earth, although we cannot see them all at once. So we think of the stars as forming a starry sphere, known as the celestial sphere.

How much of this starry sphere can we see at any one time? We can only see half of it. The half that we can see is called the sky.

In a Star Wheel, the wheel is a map of the entire celestial sphere, and the window shows us the part we can actually see at any one time; the sky.

The Shape of a Double-sided Star Wheel

The wheel is a double-sided map showing the starry sphere (celestial sphere). When we take a sphere and make a flat map of it, we have to stretch it. The stretching is especially noticeable around the edges of the map. We cannot put the whole sphere on a single map, as it would be stretched beyond recognition at the edges. For this reason we use two maps, one on each side of the wheel. Each covers about three-quarters of the sphere.

It is not possible to fit the whole sky into one window, so it is split into two. The two windows have a significant amount of overlap. Taken together the two windows represent the part of the sky that we can see at one time: half of a sphere. The horizon is a line running around the edge of the sky, so the horizon line runs around the edges of the windows.

In reality the horizon is circular, but this is distorted by the stretching involved in making a flat map. This explains the unusual shapes of the windows, and why east and west are not exactly opposite each other on the windows’ edges.

When you put the wheel in the pocket, the windows show the stars visible in that part of the sky at that particular time.

The Shape of a Single-sided Star Wheel

The wheel is a map of the stars. It shows a part of the starry sphere (celestial sphere). When we take a sphere and make a flat map of it, we have to stretch it. The stretching is especially noticeable around the edges of the map. We cannot put the whole sphere on the map, as it would be stretched beyond recognition at the edges. For this reason the wheel covers about three-quarters of the sphere.

The window represents the sky that we can see at one time: half of a sphere. The horizon is a line running around the edge of the sky, so the horizon runs around the edge of the window. The middle of the window is the part of the sky directly overhead.

In reality the horizon is circular, but this is distorted by the stretching involved in making a flat map. This is why the window looks like a squashed circle, and why east and west are not exactly opposite each other on the window.

When you put the wheel in the pocket, the window shows the stars visible in the sky at that particular time.

Distortion at the Edges

Sickle of Leo from City Wheel The City Wheel has been stretched unevenly to preserve the shapes of individual constellations at the expense of the spaces between them. This is of great benefit to beginner stargazers as the constellations are shown in the correct part of the sky and the same shape as they appear in the sky.

On the right is the actual shape of the Sickle of Leo as it appears on the City wheel. This is exactly as it appears in the sky. (In the Southern Hemishpere it will appear the other way up, but still the same shape.)

Sickle of Leo from Milky Way Wheel near centre
This technique cannot be used for the Milky Way Wheel. The Milky Way wheel shows so many stars that there are not enough empty spaces to adjust in this way. Without adjustment the constellations furthest from the centre look squashed.

The illustration on the right shows the Sickle of Leo when it is close to the centre of the Milky Way wheel. It is very little different from its actual appearance in the sky.

Sickle of Leo from Milky Way Wheel near edge

However, when it is close to the edge of the wheel, as shown here, you can see that it looks quite a different shape to the actual shape in the sky.

If you are looking for a constellation that can be seen in both the front and back windows, it is best to use the window in which it can be seen closer to the centre of the wheel.


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