Star Maps

Star maps are a traditional way to spot constellations and find your way around the night sky.  However, Earth rotates and revolves around the sun, causing constellations change their positions.  In addition, planets change their positions as they and Earth orbit the sun.

 

When and Where to Use the Acadiana Sky Star Maps

To deal with all this is, Acadiana Sky star maps are standardized for showing the sky as it would appear at 10:00 p.m. on the 15th of each month, at 30° North latitude.  Planets visible to the unaided eye at those times are included, but the moon is not because it changes its position very noticeably every night.

 

Although the maps are set for 30° North latitude, they can be helpful for anywhere in the world between about 25° and 35° North.  This includes most of the southern half of the United States, and approximates the sky as far north as the Ohio River.

 

How to Use the Star Maps

Because stars rise and set about 2 hours earlier each month as Earth orbits the Sun, each map gives other times for viewing at the beginning and end of the month.  If you want to observe at other times of night, remember that the star maps for other months can be used.  For instance, if you wish to observe at 8:00 p.m. in mid-January instead of at 10:00 p.m., use one map “backward”—December.  If you wish to observe at 4:00 a.m. in mid-January (6 hours, or 3 groups of 2 hours different from 10 p.m.), go three maps “forward” to the April map.  Remember that the planets will be in their positions for those months, though, rather than for their positions for your actual month.

 

When looking overhead, hold the star map overhead with the South marker toward the South.  Otherwise, hold the map like a book so that the direction you are looking is at the bottom.  If you are looking east, hold the map with that direction at the bottom.  If you are looking northwest, hold the map with northwest at the bottom.  The page may be sideways, but that’s OK!

 

The brightness of a star on the Acadiana Sky star maps is indicated by the size of its dot—the bigger it is, the brighter the star.  The closer a star is to the center of the map, the higher overhead it will appear in the sky.  Planets have standard-sized dots because their brightnesses vary, but all of the ones indicated are easy to see with the unaided eye.  The names of bright or significant stars are written in italics.

 

How to See Your Star Maps in the Dark

It’s best to print out the maps (or the individual map you need) rather than to try to read them from a mobile device.  The white maps on a mobile device will stun your night vision, reducing the number of stars you can see!  The larger size of a printed map will be helpful, too.  Light your maps with a flashlight that gives off red light rather than the usual white light.  A small red LED flashlight works well, or make any flashlight red with a covering of paper or plastic.  It only has to be bright enough to make the maps easy to read.  I like to hang my flashlight around my neck with a string or shoelace so I always know where I put it in the dark.  A red LED headlamp works well, too.

 

Acadiana Sky star maps were made using Cartes du Ciel software.

 

It takes a little practice to use star maps, but they will help you find your way around the sky!