xsky(1X) xsky(1X)
25 May 1993
NAME
xsky - a computerized star atlas for X
SYNTAX
xsky [-toolkitoption ...] [-LbcmfgspOBAFGKM ...]
DESCRIPTION
Xsky is a computerized star atlas running under the X11 window system.
It allows interactive viewing of the sky and construction of star
charts which may be printed on any PostScript printer.
The sky is displayed with north straight up and oriented as seen by
the naked eye. Stars are sized according to their apparent magnitude
and their colors correspond to the spectral class, as given by the
relevant catalog.
Non-stellar objects are depicted as circles, boxes, and ellipses.
Objects from the quasar catalog are circles; objects from the RNGC
catalog are elliptical if galaxies, circular if clusters, and boxes if
nebulae.
Xsky uses Athena widgets and the X toolkit exclusively, so it should
run on any X platform. This also means that most of the familiar X
command line options should work, although xsky does like to pick its
own fonts for object identification text.
Environment variables control the location of the catalog data files
and the binary dump files created by xsky. These binary dump files
are the in-core databases that xsky creates for each catalog. If this
file exists for any catalog, it will be read in place of building the
binary database for that catalog. If the file exists with a size of
zero, the catalog will be read, and the binary database will be built
and dumped to the file for use by later invocations of xsky.
OPTIONS
Xsky accepts all of the standard X Toolkit command line options as
well as the following:
-h Print a very terse (in all actuality useless) usage message.
-L Start with a large display. After positioning the small
outline on the screen, xsky resizes to fill the entire screen.
-b Draw the sky in black-and-white mode even if this is a color
display. The background remains black, but stars are white
instead of colored.
-c catlist
Set the initial list of displayed catalogs to catlist. This
is a comma-delimited list, with each catalog being specified
by its menu name in the catalog selection menu.
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-m mag Set the initial limiting magnitude to mag. Stars dimmer than
this will not be displayed.
-f font Set the font for object identification to font. This font is
used for object names which are not Greek letters.
-g font Set the font for Greek letters to font. This font is used for
Bayer designations of stars from the Yale Bright Star Catalog.
-s scale
Set the initial display scale to scale pixels per degree.
-p position
Set the initial position of the display to position. This is
a string in the format <nnh hhm nns.nnn, +/-nnd nn' nn".nn>
specifying the right ascension and declination of the display
center.
-OBAFGKM color
Each of these option letters represents a stellar spectral
class. Specifying one of these options changes the color of
the stars in that spectral class to color. Stars of class W
are represented as O, and stars of classes C, R, N, and S are
represented as M. Unknown or undecipherable spectral classes
are rendered as white.
-bin Terminate after reading the text catalogs and building the
binary databases. All contact with the X Window System is
avoided; this option allows building the binary databases from
an ordinary terminal. This option must be used alone; it will
not work (nor does it make sense) with any other options.
CONTROL MENU
Info Brings up a panel showing the size and grid spacing of the
display. There are also two text boxes containing information
which may be edited to change the values of magnitude limit
(for stars) and display scale.
Catalogs
Brings up a menu which allows selection of the catalogs to be
displayed.
Zoom In Increases the magnification of the display. Each zoom step
increases the display scale by 20%.
Zoom Out
Decreases the magnification of the display. Each zoom step
decreases the display scale by 20%.
Grid Draws lines of right ascension and declination on the sky
display. The "Info" display gives the spacing of the lines.
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The lines are unlabelled, but the spacing and display center
will allow determination of the line coordinates.
Hide IDs
Removes all object identifications from the display. They may
be recalled by toggling "Hide IDs" again. IDs are created by
clicking the center mouse button on an object; see below.
Erase IDs
Erases all object identifications from the display. Once
erased, identifications may not be recalled.
Find Brings up a panel with a text widget into which the name or
designation of an object may be edited. Clicking the Find
button on the panel will then cause the display to be moved to
that object if it can be identified by the given name or
designation. At present, only stars can be located by name.
The file "catalogs.doc" documents the object designations that
can be entered on the Find panel.
Chart Writes a file called "starchart.ps" which may be printed on
any PostScript printer for an exact representation of the
current sky display, including identifying text and grid
lines.
Quit Leave xsky.
INTERACTION
The following interactions allow manipulation of the sky display.
Note that the mouse cursor is the original Starship Enterprise, flying
toward the top of the screen. The forward tip of the Enterprise's
"saucer section" is the cursor hotspot.
+ The horizontal scrollbar at the bottom of the sky display scrolls
the sky due east/west.
+ The vertical scrollbar at the right of the sky display scrolls
the sky due north/south.
+ Clicking the left mouse button on a displayed object brings up
the catalog information for that object.
+ Clicking and holding the center mouse button on a displayed
object brings up an outline box which follows the mouse;
releasing the center button replaces the box with identifying
text placed at that location.
+ Clicking the center mouse button with the Shift key depressed
removes the identifying text under the mouse pointer.
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+ Clicking the right mouse button on any point in the sky display
recenters the display on that point.
OTHER ACTIONS
The "Display center" at the top of the main display is an editable
text buffer. To move to a known location on the sky, simply edit this
buffer to contain the desired right ascension and declination,
following the general format shown in the buffer. Hitting the return
key while in the buffer causes the sky display to be updated.
FILES
$YBS_PATH/ybs.dat
The Yale Catalog of Bright Stars
$YBS_BIN_PATH/ybs.bin
A dump of the binary in-core database for the YBS catalog
$RNGC_PATH/rngc.dat
The Revised New General Catalog of Non-Stellar Objects
$RNGC_PATH/rngc_desc.tab
RNGC catalog description abbreviations
$RNGC_BIN_PATH/rngc.bin
A dump of the binary in-core database for the RNGC catalog
$QSO_PATH/qso.dat
The Revised Optical Catalog of Quasi-Stellar Objects
$QSO_BIN_PATH/qso.bin
A dump of the binary in-core database for the QSO catalog
$STARNAME_PATH/starnames.dat
Common star names by HR number for use with the YBS
database.
The file xskyenv defines a number of other environment variables for
additional catalogs supported by, but not shipped with, xsky.
BUGS
The -L option does not work except as a work procedure, and work
procedures are turned off.
AUTHOR
Terry R. Friedrichsen, Sunquest Information Systems.
(terry@venus.sunquest.com)
ACKNOWLEDGEMENTS
The precession algorithm and precession constants are from
PRECESS.BAS, written by PC Leyland.
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Brian Wing greatly sped up the screening of objects to determine
whether they fall in the current display.
Jim Sharpe was the original beta tester, making many useful
suggestions and improving the user interface.
The supplied object databases are stripped-down versions of databases
supplied by the National Space Sciences Data Center (NSSDC) at the
Goddard Spaceflight Center in Greenbelt, Maryland, which is
administered by the National Aeronautics and Space Administration
(NASA).
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