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)