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
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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
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(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
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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 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
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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.
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