glenda.party
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term% cat index.txt
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  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 be‐
       comes  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 ob‐
       jects' 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  de‐
              grees, 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
              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.

       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 ascension and declination, azimuth and  al‐
              titude,  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 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  >  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 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.

       astro option
              Run astro(7) with the specified options (to which  will  be  ap‐
              pended  -p),  to discover the positions of the planets.  Astro's
              -d and -l options can be used to set the time and place; by  de‐
              fault, it's right now at the coordinates in /lib/sky/here.  Run‐
              ning 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  posi‐
              tions.

       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 stippled 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  inferior  planets;  upper
              case  for superior); the sun, moon, and earth's shadow are unla‐
              beled 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 galaxies.

              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
              512Ã512; options dx n and dy n set the x and y extent.  The  op‐
              tion  zenithup  orients the map so it appears as it would in the
              sky at the time and location used by the astro command (q.v.).

              The output is designed to look best on  an  LCD  display.   CRTs
              have  trouble  with the thin, grey lines and dim stars.  The op‐
              tion nogrey uses white instead of grey for  these  details,  im‐
              proving  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 ap‐
              proximately  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 500Ã500 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 images.  Default is -1.0.
              Negative values display white stars, positive black.  The images
              look  best  on  displays with depth 8 or greater.  Scat does not
              change the hardware color map, which should be set externally to
              a  grey scale; try the command getmap gamma (see getmap(9.1)) 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

       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 (but not distributed) by permis‐
       sion.  The Digitized Sky Survey, 102 CD-ROMs, is not  distributed  with
       the system.



                                                                       SCAT(7)