SCAT(7)                                                   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 provides an interface to
          astro(7) to plot the locations of solar system objects.
          Finally, it displays images from the Space Telescope Science
          Institute's Digitized 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
               (Gx=galaxy, 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)=unverified 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 Cat-
               alogue.  Output identifies the visual and photographic
               magnitudes, 2000.0 coordinates, proper motion, spectral
               type, multiplicity and variability class, and HD num-
               ber.

          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

     SCAT(7)                                                   SCAT(7)

               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, galactic 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.

          "α 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 out-
               put 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 coordinates 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.

          mars The planets are identified by their names.  The names
               shadow and comet refer to the earth's penumbra at lunar
               distance and the comet installed in the current
               astro(7). The output is the planet's name, right ascen-
               sion and declination, azimuth and altitude, and phase
               for the moon and sun, as shown by astro.  The positions
               are current at the start of scat 's execution; see the
               astro command in the next section for more information.

          The commands are:

          add item
                 Add the named item to the set.
          keep class ...
                 Flatten the set and cull it, keeping only the speci-
                 fied classes.  The classes may be specific NGC types,
                 all stars (sao), all NGC objects (ngc), all M objects

     SCAT(7)                                                   SCAT(7)

                 (m), all Abell clusters (abell), or a specified
                 brightness range.  Brightness ranges are specified by
                 a leading > or < 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 flattens the set so scat holds all the informa-
                 tion 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.
          astro option
                 Run astro(7) with the specified options (to which
                 will be appended -p), to discover the positions of
                 the planets.  Astro's -d and -l options can be used
                 to set the time and place; by default, it's right now
                 at the coordinates in /lib/sky/here.  Running astro
                 does not change the positions of planets already in
                 the display set, so astro may be run multiple times,
                 executing e.g.  add mars each time, to plot a series
                 of planetary positions.
          plot option
                 Expand and plot the set in a new window on the
                 screen.  Symbols for NGC objects are as in Sky Atlas
                 2000.0, except that open clusters are shown as stip-
                 pled disks rather than circles.  Abell clusters are
                 plotted as a triangle of ellipses.  The planets are
                 drawn as disks of representative color with the first
                 letter of the name in the disk (lower case for infe-
                 rior planets; upper case for superior); the sun,
                 moon, and earth's shadow are unlabeled disks.
                 Objects larger than a few pixels are plotted to
                 scale; however, scat does not have the information
                 necessary to show the correct orientation for galax-
                 ies.
                 The option nogrid suppresses the lines of declination
                 and right ascension.  By default, scat labels NGC
                 objects, Abell clusters, and bright stars; option
                 nolabel suppresses these while alllabel labels stars
                 with their SAO number as well.  The default size is
                 512×512; options dx n and dy n set the x and y
                 extent.  The option zenithup orients the map so it
                 appears as it would in the sky at the time and loca-
                 tion used by the astro command (q.v.).
                 The output is designed to look best on an LCD dis-
                 play.  CRTs have trouble with the thin, grey lines

     SCAT(7)                                                   SCAT(7)

                 and dim stars.  The option nogrey uses white instead
                 of grey for these details, improving visibility at
                 the cost of legibility when plotting on CRTs.
          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 displayed 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 500×500 pixel block from the survey con-
                 taining 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 images.
                 Default is -1.0.  Negative values display white
                 stars, positive black.  The images look best on dis-
                 plays with depth 8 or greater.  Scat does not change
                 the hardware color map, which should be set exter-
                 nally to a grey scale; try the command getmap gamma
                 (see colors(1)) on an 8-bit color-mapped display.

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

          Draw a finder chart for Uranus:
               uranus
               expand 5
               plot

          Show a partial lunar eclipse:
               astro -d
               2000 07 16 12 45
               moon
               add shadow
               expand 2
               plot

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

     SCAT(7)                                                   SCAT(7)

          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 constellation names.

          The data was provided by the Astronomical Data Center at the
          NASA Goddard Space Flight Center, except for NGC2000.0,
          which is Copyright © 1988, Sky Publishing Corporation, used
          (but not distributed) by permission.  The Digitized Sky Sur-
          vey, 102 CD-ROMs, is not distributed with the system.