StarChart is a standalone program that will plot a portion of the
night sky on the Macintosh screen. Several new features have been
added to this version of StarChart. Here is how to use the program:
1\. StarChart will plot a section of the sky based upon information
given to it by the user. Under the StarChart menu, you will see four
menu options. The first is Plot New Chart.... After choosing this
command, you will see a dialog box where you can enter three numbers,
View Angle, Right Ascension and Declination. If you don't know what
these terms mean, the picture may help you. Note that the View Angle
must be between 1 and 360, Right Ascension must be between 0 and 24,
and Declination must be between -90 and 90. Click the mouse on Plot to
begin plotting that portion of the sky.
2\. The next menu choice under the StarChart menu will bring up a list
of the 88 constellations. StarChart will plot the section of the sky
that contains the constellation that you choose.
3\. The next menu choice will list Messier objects. StarChart will
plot the section of the sky that contains that Messier object. The
object will be plotted at or near the center of the screen.
4\. The next menu choice will list popular star names for 88 of the
brightest stars in the sky. As above, after choosing one of these,
StarChart will plot that portion of the night sky. The star chosen
will be plotted at or near the center of the screen.
5\. StarChart will take from a few seconds to several minutes to plot
the sky. The plotting time depends on the coordinates given.
Generally, the farther away from 0 the declination gets, the longer
the plotting time. Also, larger view angles will increase the plotting
time. Just click the mouse if you wish to cancel the plot at any time.
6\. After StarChart has finished plotting, you may retrieve data about
any object on the screen by pointing to it with the mouse and
clicking. A menu will appear in the menu bar that contains information
on that object. If the star does not have a popular name, the title of
the menu will be its abbreviated Greek designation. For example, the
star "Beta Scorpio" would be abbreviated "BETSCO". The Greek letter
usually represents the rank in brightness in that constellation. For
example, "Beta Scorpio" would probably be the second brightest star in
the constellation Scorpio (but this is not always true). If the star
does have a popular name, that name will be the title of the menu, and
its Greek designation will be the first entry under the menu bar.
Below this information is the Right Ascension, Declination, Magnitude
and Color Index of the star. The magnitude will range any where from
-.1 to 9.9, the larger the number, the less bright the object. (A few
Messier objects had magnitudes above 9.9. These were entered in the
database as "9.9".) The Color Index is an indicator of the color of
the star. It ranges from -.25 to +2.5. A lower number means the star
is bluer; a higher number means the star is redder. Note that Messier
objects do not have a Color Index.
7\. Under the "Draw" menu is the option "Draw Grid". Choosing this
option will draw a labeled grid across the screen, with lines
representing hours of Right Ascension and 10 degrees incriments in
declination. This facilitates star-hopping with a telescope.
8\. By holding down the command key, you may draw straight lines
across the screen. This is useful for outlining constellations or
other objects. The lines that you draw may be erased with the "Erase
Lines" option in the "Draw" menu.
9\. The third option under the "Draw" menu allows you to invert the
screen so that the stars appear black on a white screen. This is
useful in case you want to print the contents of the screen using the
Command-Shift-4 key combination.
10\. The "Brightness" menu allows you to selectively plot certain
magnitudes of stars. All magnitudes of stars will be plotted if "Plot
All Stars" is chosen. If you wish to see only stars between magnitudes
2.0 and 2.9, choose that option. Note that you can choose any
combination of magnitudes; for example you can choose to see only
stars brighter than 1.0 and dimmer than 5.0. Choosing "Plot All Stars"
cancels all options previously selected. Note that limiting the stars
that StarChart has to plot speeds up the plotting greatly.
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