|
|
| |
SCAT(1) |
FreeBSD General Commands Manual |
SCAT(1) |
scat - sky catalogue and Digitized Sky Survey
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 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 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 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 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 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 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 The output is the planet's name, right ascension
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 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 flattens
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 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
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 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 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
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 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 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 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.
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
/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 Survey, 102 CD-ROMs, is not distributed with
the system.
Visit the GSP FreeBSD Man Page Interface. Output converted with ManDoc. |