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SCAT(7)                Miscellaneous Information Manual                SCAT(7)



NAME
       scat - sky catalogue and Digitized Sky Survey

SYNOPSIS
       scat

DESCRIPTION
       Scat  looks  up items in catalogues of objects outside the solar system
       and implements database-like manipulations on sets of such objects.  It
       also displays images from the Space Telescope Science Institute's Digi-
       tized Sky Survey, keyed to the catalogues.

       Items are read, one per line, from the standard input and looked up  in
       the  catalogs.   Input  is  case-insensitive.  The result of the lookup
       becomes the set of objects available to the database  commands.   After
       each  lookup  or command, if more than two objects are in the set, scat
       prints how many objects  are  in  the  set;  otherwise  it  prints  the
       objects'  descriptions  or  cross-index listings (suitable for input to
       scat).  An item is in one of the following formats:

       ngc1234
              Number 1234 in the New General Catalogue of Nonstellar  Objects,
              NGC2000.0.   The output identifies the type Pl=planetary nebula,
              OC=open  cluster,   Gb=globular   cluster,   Nb=bright   nebula,
              C+N=cluster associated with nebulosity, Ast=asterism, Kt=knot or
              nebulous region in a galaxy, ***=triple  star,  D*=double  star,
              ?=uncertain, -=nonexistent, PD=plate defect, and (blank)=unveri-
              fied or unknown), its position in 2000.0 coordinates,  its  size
              in minutes of arc, a brief description, and popular names.

       ic1234 Like NGC references, but from the Index Catalog.

       sao12345
              Number  12345  in  the Smithsonian Astrophysical Star Catalogue.
              Output identifies the visual and photographic magnitudes, 2000.0
              coordinates,  proper  motion,  spectral  type,  multiplicity and
              variability class, and HD number.

       m4     Catalog number 4 in Messier's catalog.  The output  is  the  NGC
              number.

       abell1701
              Catalog  number 1701 in the Abell and Zwicky catalog of clusters
              of galaxies.  Output  identifies  the  magnitude  of  the  tenth
              brightest  member  of  the  cluster,  radius  of  the cluster in
              degrees, its distance in megaparsecs, 2000.0 coordinates, galac-
              tic  latitude and longitude, magnitude range of the cluster (the
              `distance group'), number of  members  (the  `richness  group'),
              population per square degree, and popular names.

       planetarynebula
              The set of NGC objects of the specified type.  The type may be a
              compact NGC code or a full name, as above, with no blank.

       " umi" Names are provided in double quotes.  Known names are the  Greek
              letter  designations,  proper  names  such as Betelgeuse, bright
              variable stars, and some proper names of stars, NGC objects, and
              Abell  clusters.  Greek letters may be spelled out, e.g.  alpha.
              Constellation names must be the three-letter abbreviations.  The
              output  is the SAO number.  For non-Greek names, catalog numbers
              and names are listed for all objects with names  for  which  the
              given name is a prefix.

       12h34m -16
              Coordinates  in  the  sky are translated to the nearest `patch',
              approximately one square degree of sky.  The output is the coor-
              dinates  identifying  the patch, the constellations touching the
              patch, and the Abell, NGC, and SAO objects in  the  patch.   The
              program prints sky positions in several formats corresponding to
              different precisions; any output format is understood as input.

       umi    All the patches in the named constellation.

       The commands are:

       add item
              Add the named item to the set.

       keep class ...
              Flatten the set and cull it, keeping only the specified classes.
              The  classes may be specific NGC types, all stars (sao), all NGC
              objects (ngc), all M objects (m), all Abell clusters (abell), or
              a  specified  brightness range.  Brightness ranges are specified
              by a leading >&gt; or <&lt; followed  by  a  magnitude.   Remember  that
              brighter objects have lesser magnitudes.

       drop class ...
              Complement to keep.

       flat   Some items such as patches represents sets of items.  Flat flat-
              tens the set so scat holds all the information available for the
              objects in the set.

       print  Print the contents of the set.  If the information seems meager,
              try flattening the set.

       expand n
              Flatten the set, expand the area of the sky covered by  the  set
              to be n degrees wider, and collect all the objects in that area.
              If n is zero, expand collects all objects in  the  patches  that
              cover the current set.

       plot option
              Expand  and  plot  the  set  on  the screen.  The only option is
              nogrid to suppress the lines of declination and right ascension.
              Symbols for NGC objects are as in Sky Atlas 2000.0.  Abell clus-
              ters are plotted as a triangle of ellipses.

       plate [[ra dec] rasize [decsize]]
              Display the section of the Digitized  Sky  Survey  (plate  scale
              approximately  1.7  arcseconds  per pixel) centered on the given
              right ascension and declination or, if no position is specified,
              the  current set of objects.  The maximum area that will be dis-
              played is one degree on a side.   The  horizontal  and  vertical
              sizes may be specified in the usual notation for angles.  If the
              second size is omitted, a square region  is  displayed.   If  no
              size is specified, the size is sufficient to display the centers
              of all the objects in the current set.  If a single object is in
              the  set,  the 500500 pixel block from the survey containing the
              center of the object is displayed.  The survey is stored in  the
              CD-ROM juke box; run 9fs juke before running scat.

       gamma value
              Set  the  gamma  for  converting  plates to bitmaps.  Default is
              -1.0.  Negative values display white stars, positive black.  The
              images  look  best  on  displays  with  ldepth 3.  Scat does not
              change the hardware color map, which should be set externally to
              a grey scale; try the command fb/getmap gamma (see getmap(9.1)).

EXAMPLES
       Plot the NGC objects and naked-eye stars in Orion.
            ori
            keep ngc <6
            plot nogrid

       Draw a map of the Pleiades.
            "alcyone"
            expand 1
            plot

       Show a pretty galaxy.
            ngc1300
            plate 10'

FILES
       /lib/sky/*.scat

SOURCE
       /sys/src/cmd/scat

SEE ALSO
       astro(7)
       /lib/sky/constelnames    the three-letter abbreviations of the constel-
       lation names.

       The data was provided by the Astronomical Data Center at the NASA  God-
       dard  Space  Flight  Center,  except  for NGC2000.0, which is Copyright
       1988, Sky Publishing Corporation, used by  permission.   The  Digitized
       Sky Survey, 102 CD-ROMs, is not distributed with the system.



                                                                       SCAT(7)