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 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
clusters of galaxies. Output identifies the magnitude
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SCAT(7) SCAT(7)
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.
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
(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
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SCAT(7) SCAT(7)
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 clusters 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 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 bitmaps.
Default is -1.0. Negative values display white
stars, positive black. The images look best on dis-
plays with ldepth 3. Scat does not change the hard-
ware 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'
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SCAT(7) SCAT(7)
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
by permission. The Digitized Sky Survey, 102 CD-ROMs, is
not distributed with the system.
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