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ZenithStarChartOrbitTrack, OrbitMark, DeepSkyMark

4.5 The StarNames Function

StarNames can be used to label individual stars in a constellation. This function can be passed via the options Epilog or Prolog to any of the star chart functions.

Labeling stars in a constellation.

For example, you can label the stars in the constellation Ursa Major, also known as the Big Dipper, by simply passing the option Epilog -> StarNames[UrsaMajor] to any star chart.

Similarly, you can identify all the stars in the Pleiades star cluster by using the option Epilog -> StarNames[Taurus, MagnitudeRange->6]. Pleiades, also known as the Seven Sisters, contains many stars clustered in a small region of the sky in the constellation of Taurus. Some of the stars are on the edge of naked-eye visibility, so to label them you need to set a lower magnitude limit.

Typically, stars are named with Greek letters, with Alpha (alpha) commonly referring to the brightest star in a given constellation. In the case of Pleiades, the central star is named Eta (eta). Eventually the Greek alphabet is exhausted and numbers are used to name stars. Fainter stars in Pleiades, therefore, are called simply 19, 23, 27, and so on. Variable stars, however, are named using a special two-letter system. For instance, there is a faint variable star called BU in Pleiades.

The star Zeta (zeta) Ursa Majoris, also known as Mizar, on the left center of this graphic is the famous double star visible to the naked eye. A mere 0.2 degrees away is its partner Alcor, which is not visible in the graphic.

In[25]:=RadialStarChart[UrsaMajor,
StarColors -> True,
ConstellationLabels -> True,
Epilog -> {RGBColor[1,1,.5],
StarNames[UrsaMajor]}];

This star chart uses StarNames to label the seven brightest stars in the Pleiades star cluster.

In[26]:=RadialStarChart[Eta.Taurus,
RadialAngle -> 1*Degree,
MagnitudeScale -> 0.5,
Epilog -> StarNames[Taurus,
MagnitudeRange->5.6]];

Font Sizes and Names

A default font name and various font sizes are used throughout the star charts and other functions. The default font is "Helvetica", but you might want to use a different font for display purposes on some platforms. To do this set $DefaultFontName to the name of the font you want.

Sometimes, the size of the fonts can look small on the screen, but this is adjustable, too. By setting $DefaultFontScale to a scale factor other than 1, you can increase or decrease the font size. By default, the scale factor is 1.

This modifies the values of $DefaultFontName and $DefaultFontScale to change the font name and size used in this graphic. Note that the brighter stars are now labeled using double-sized "Times-Italic" font. The labels above the stars are still in Greek letters, or "Symbol" font, but are now double sized, too.

In[27]:=Block[{$DefaultFontName = "Times-Italic",
$DefaultFontScale = 2},
StarChart[Orion,
MagnitudeRange -> 3.5,
StarLabels -> True,
Epilog -> StarNames[Orion]]];

ZenithStarChartOrbitTrack, OrbitMark, DeepSkyMark



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