Latitude is a measure of the angular separation in degrees away from the equator. Note that these circles do not cross one another (they’re parallel), and each circle is smaller than the one before as one moves north or south away from the equator. More circles called parallels of latitude can be found in 10 to 15 degree increments as one moves north or south away from the equator and toward the two attachment points. One could travel around the world while remaining on the equator and never be at a latitude of more than 0° north or south. The horizontal lines, or circles, on the globe are called parallels of latitude. The equator, or the largest circle half way between the two points were the globe is attached to its stand, is a special parallel that is designated as the zero degree latitude. Aldebaran, a bright star, is not named on the map above, but it can be found at Dec +16.5 degrees, Ra 4:36. Similarly, the intersection on the celestial sphere of the lines representing declination +16.5°, and 4 hours, 36 minutes right ascension is where the star Aldebaran is found in the constellation of Taurus. For instance, if I know that Ashton, Maryland is located at N39.14° and W77.01°, I can locate Ashton on the globe by finding the intersection of the N39.14° and W77.01° lines on a globe or on a map. The intersection of two lines is a coordinate that represents a point on the surface of the sphere. Both spheres have horizontal and vertical circles, sometimes called lines, that represent north-south and east-west spatial relationships. Now to take on the two coordinate systems. If the Sun, Moon, a planet, or some other celestial object happens to appear within a constellation’s borders, it is said to be located in that constellation. Secondarily, a constellation is an area of the sky (country), which is delineated by the purple border. The interconnecting blue lines (highways) aid in identifying the spatial relationships between the constellation’s stars by guiding our eye from one star to the next. In this chart Orion appears as a stick figure torso with a belt of three stars and what is usually depicted as a shield and raised club in the chart. First, and foremost, a constellation is a grouping of stars (cities). There are two ways to think of constellations. Referring to the accompanying star chart, which is made specifically for Ashton, MD at 8pm EDT on March 15, 2015, find Orion located below and to the right of the zenith (the red circled “ z“).
Highways connecting the cities can be found on maps representing smaller portions of the Earth’s surface.Ĭonstellations are the man-made corollaries to the countries, cities and highways that we find on globes and maps representing the Earth surface. The cities are generally regarded as fixed points that may from time to find themselves in one country or another as political boundaries are redrawn. We can see on a globe that the land areas are apportioned among countries with borders (lines) drawn to demarcate each country’s political, or man-made boundaries.
#Whats my star chart how to
Refresh your understanding of a conceptual celestial sphere, if needed, by reading How to begin Observing the Night Sky. For this reason, a brief review of a globe is a good starting point for understanding a star chart. A globe is a spherical representation of the Earth’s surface that shares several common attributes with the celestial sphere. An observer looking outward from the Earth is gazing upon the celestial sphere. There are two related spherical representations to consider in order to learn how to read a a star chart – a globe and the celestial sphere. Think of the Earth as the terrestrial sphere situated at the center of the celestial sphere.
As an aid to understanding this material, I have referenced and inserted thumbnail images of graphics that can be clicked for a larger view. This article is written under the Constellations Project, and it builds on How to begin Observing the Night Sky by describing the celestial coordinate system and other details that appear on the sky maps presented in each month’s edition of Scope Out Next Month.
#Whats my star chart series
Welcome to the second in my series of guides to observing the night sky.
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