- A Start Chart is a graphical representation of the night sky.
- Knowing the approximate size of stars and constellations can help in locating them.
- Star Charts help identify stars, constellations, planets, galaxies, and deep-space objects.
- The North Star (Polaris) is a stationary reference point used for navigation.
What is a Star Chart
- Displays the positions of stars and constellations and identifies their location based on date, time, and place.
- Star Charts are also known as celestial maps or sky charts.
- The first star chart is credited to Hipparchus, the creator of trigonometry. It’s believed that Hipparchus mapped the stars approximately two thousand years ago (129 BC.).
Preparing to Use a Star Chart
If you’re going to use a Star Chart, you’ll need to do a little preparation to prepare for your big night out in the backyard.
Obtaining a Star Chart: Print or Purchase
It may say a tad boring, but we recommend printing (on paper!) a star chart before you head out to the backyard for star gazing. Yes, you certainly can (and we have) used a cell phone, laptop, or iPad to view a start chart. Truth be told, most electronic display screens will cause your pupils to dilate from the brightness. Dilated pupils allow less light into your eye, so you’ll detect fewer stars.
If you have a paper printout, a book (that’s our favorite Night Sky Book!), or a spinning laminated map (best), you’ll need to be able to see it in the dark. You can either make your own red light flashlight or snag one online.
All is not lost if you don’t have a paper copy of a star chart. You can use a digital display but try (no laughter!) to only use one eye. Yes, pretend you’re a pirate and can only open one eye to look at the display. When you start looking at the night skies, use the other eye. Within a few minutes, the eye you used to look at the bright screen will dilate to the same level as the other eye.
Everything is moving!
It’s essential to understand that the Earth is rotating on its axis while orbiting around the sun. The position of stars, constellations, and planets will appear in different locations throughout the night and throughout the year.
The image above is a time-lapse photo of the North Star (Polaris). Do you see the circular star “trails?” The very center of the stars is Polaris (North Star.) It’s a great reference point. Sailors have used Polaris for thousands of years because it seems stationary (it’s actually moving in a tiny circle) and is used as a navigation aid.
Locating the North Star
Start by aiming your nose toward the North Star Polaris. Need help to find it? Here’s a quick breakdown.
- Locate the Big Dipper (Ursa Major)
- Draw an imaginary line from the far side of the Big Dippers cup to the “tail” of the Little Dippers (Ursa Minor) handle.
- The tip of the Little Dippers handle is Polaris, the North Star.
- Orient your body so that you’re facing Polaris. You’re now facing North.
How to Use a Star Chart
- Now that you’re facing North hold the map above your head (straight up!). Let’s look at the chart below.
- Orient the chart to match the orientation of the Big Dipper (Ursla Major.)
- Rotate the chart so that the current month of the year faces North.
- Pro Tip: There’s a lot to be said for planispheres that spin on a central axis; you’ll be able to adjust the planisphere based on the month and day. When printing out the chart above, you’re the central axis, and you’ll rotate the chart. As you turn the chart, you’re rotating seasons of the year.
- Now that you’ve found Polaris and orientated the map, it’s time to find a few constellations!
Size Matters-Putting Your Hands to Good Use
One part of the equation is knowing where to look for stars, constellations, and galaxies. A rough approximation of their size will help you understand what size to expect.
- Hold your arm out at shoulder height and raise your right hand. Make a thumbs up. The width of your thumb is approximately two degrees.
- Hold your arm out at shoulder height and raise your right hand. Make a fist, knuckles down, with the thumb tucked into your palm. The measured distance is approximately ten degrees.
- Hold your arm out at shoulder height and raise your left hand. Spread your fingers out. The measured distance is approximately twenty degrees.
|Object||Degree (Rough size approximation)|
|Spread Fingers (one hand)||20°|
|Spread Fingers (both hands)||40°|
Locating Stars and Constellations
The key to locating constellations is first to find nearby reference stars. The shaded area of the chart displays the Milky Way. Each “dot” represents a star. The larger the dot, the brighter the star. Start your exploration with bright stars and the constellations near them.
Use the size chart above to help determine if you’re looking at the right “size” area. It’s an approximate measurement. A little bigger or smaller than our example is still OK. (If you have tiny baby hands, our method might not work well for you!)
Now that we have a rough approximation of size let’s find a few constellations! We’ve broken out a few significant constellations based on the months of the year.
|Canis Major||Spread Fingers||Sirus||Jan-Feb|
|Cancer||Spread Fingers||Beehive Cluster||Mar-Apr|
|Coma Berenices||Fist||North of Virgo||May-Jun|
|Corona Borealis||Fist||Between Boots & Hercules||Jun-Jul|
|Capricornus||Spread Fingers||SE Quadrant||Aug-Sep|
|Aquarius||Both hands||S of Pegasus||Sep-Oct|
|Andromeda||Fist||NE of Pegasus||Oct-Nov|
|Camelopardalis||Spread Fingers||Between Ursa Major and Minor||Dec-Jan|
Happy star gazing!
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- Basic guide to the solar system
- Lots of photographs, illustrations, and graphics
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- $18.88Buy Now on Amazon
- Give the exact location of stars relative to the horizon
- Reverse side contains useful information
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- Help search the skies with confidence
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The image featured at the top of this post is ©Allexxandar/Shutterstock.com.