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Using PlanetChartUsing RadialStarChart

9.3 Using StarChart

StarChart shows a section of the sky. There are several ways to call this function.

First, you can supply a constellation name, such as Scorpius, and you will see a region that includes that constellation. This is the standard way to use the function. Instead of a constellation name, you can also supply any other type of object, such as a star or planet name, to view the region surrounding that object.

Second, you can supply a bounding rectangle to specify the minimum and maximum right ascension and declination that you wish to view. The easiest way to obtain numbers for the rectangle is to use CommandKey-OptionKey and copy on a previous StarChart graphic, and then paste the result into a new StarChart call.

In the graphic returned by StarChart the green lines join together some of the brighter stars to form constellations. The blue line represents the ecliptic; all the planets and the Moon move approximately along this line. The Sun moves precisely along the ecliptic.

To display red dots for the positions of all the planets at the current date, you can use the option setting Planets -> All. To display a subset of all the planets you can use, for example, Planets -> {Mercury, Venus, Mars}. You can use the Sun and Moon in the list, but they are displayed as yellow and gray dots, respectively. The default setting is Planets -> None. Label planets with the option setting PlanetLabels -> True. If you use the setting StarColors -> True, accurate colors are used for the planets, rather than simply red dots.

The region below the local horizon is shaded with a brown area by using the option setting Horizon -> True. If you set the option Skyline to specific graphic primitives, involving Line, Rectangle, Disk, Circle, Point, Polygon, and Text, then a sky line is mapped along the horizon line.

By default, constellation outlines and the ecliptic line are drawn. These are suppressed by using the option settings Constellations -> False and Ecliptic -> False.

Use the option setting ConstellationLabels -> True to display the names of the constellations that appear in the field of view. The option setting StarLabels -> True displays the names of the brightest stars. Another way to identify a particular star in the output from StarChart is to select the graphic, use CommandKey and click near a star. Then copy and paste the pair of numbers into FindNearestObject to get the name of the star nearest to the point where you clicked. You can also find the nearest deep sky object or planet with the FindNearestObject function.

One way to label all the stars in a particular constellation is to use the expression StarNames[constellation] as part of an Epilog option. For example, the option setting Epilog -> {StarNames[Scorpius], StarNames[Ophiuchus]} labels all the stars in the given constellations.

StarChart is based initially on a database of the 300 brightest stars. A set of the 3,000 brightest stars is used if you load the file called Astronomer`Star3000`. This file contains all the stars visible to the naked eye. An additional file, called Astronomer`Star9000`, contains the 9,000 brightest stars.

To filter out a subset of the stars use the option MagnitudeRange. As an example, MagnitudeRange -> {3, 5} displays only those stars whose magnitudes are between 3 and 5. The default is MagnitudeRange -> {-Infinity, Infinity}.

You can enhance the brightness of stars by using the option MagnitudeScale. This is useful if you zoom into a small area of the sky, since you can use, say, MagnitudeScale -> 2 to artificially double the brightness of the stars so that bigger dots appear in the graphic output.

Use the option setting Background -> RGBColor[r,g,b] when you want to create a colored background for the sky field. The default is white, and in this case black stars and text are used. If the background is a dark color, then stars and text are displayed in white. Stars can also be colored according to their visible spectral type; to use this feature choose the option setting StarColors -> True.

The option settings Clusters -> True, Nebulae -> True, and Galaxies -> True, will display special symbols indicating star clusters, nebulae, and galaxies. You can additionally label the objects using the options ClusterLabels -> True, NebulaLabels -> True, and GalaxyLabels -> True.

Finally, as with all graphics functions in Scientific Astronomer, StarChart inherits the standard set of Graphics options.

Using PlanetChartUsing RadialStarChart