What Is a Star Chart?

Attributes

• A star chart displays the visible constellations during a certain time of year, while looking in a certain direction. Many star charts also show the relative brightness of stars within constellations, which can be helpful for beginners attempting to locate formations. Additionally, star charts are only accurate during certain hours, since the stars move over the course of the night.

North and South

• Different star charts are required for the northern and southern hemispheres, since they have differing views of the stars. Some constellations are only visible from the southern hemisphere, while some are only visible from the northern. These constellations are known as circumpolar constellations. The southern circumpolar constellations are Carina, Centaurus and The Southern Cross, while the northern circumpolar constellations are Casseopia, Cepheus, Draco, Ursa major and Ursa minor.

Planispheres

• Planispheres are a specialty type of star chart, where two disks sit on top of each other. These disks can be rotated according to the season and time of day, giving an accurate picture of the sky in any condition. Many planispheres include multiple disks or double-sided disks for the different seasons and hemispheres.

Magnitude

• All types of star charts can be further subdivided as either fifth or sixth magnitude. Fifth-magnitude star charts display only the brightest stars, isolating the constellations and making the chart easier to use for beginners. In addition to the bright stars, sixth-magnitude star maps show dimmer stars and some deep-space objects. These items are typically harder to find (especially with the naked eye) and involve less-known celestial objects.