335 lines
8.7 KiB
Text
335 lines
8.7 KiB
Text
.TH SCAT 7
|
||
.SH NAME
|
||
scat \- sky catalogue and Digitized Sky Survey
|
||
.SH SYNOPSIS
|
||
.B scat
|
||
.SH DESCRIPTION
|
||
.I 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
|
||
.IR 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.
|
||
.PP
|
||
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,
|
||
.I scat
|
||
prints how many objects are in the set; otherwise it
|
||
prints the objects'
|
||
descriptions or cross-index listings (suitable for input to
|
||
.IR scat ).
|
||
An item is in one of the following formats:
|
||
.TP
|
||
.B ngc1234
|
||
Number 1234 in the New General Catalogue of
|
||
Nonstellar Objects, NGC2000.0.
|
||
The output identifies the type
|
||
.RB( Gx =galaxy,
|
||
.BR Pl =planetary
|
||
nebula,
|
||
.BR OC =open
|
||
cluster,
|
||
.BR Gb =globular
|
||
cluster,
|
||
.BR Nb =bright
|
||
nebula,
|
||
.BR C+N =cluster
|
||
associated with nebulosity,
|
||
.BR Ast =asterism,
|
||
.BR Kt =knot
|
||
or nebulous region in a galaxy,
|
||
.BR *** =triple
|
||
star,
|
||
.BR D* =double
|
||
star,
|
||
.BR ? =uncertain,
|
||
.BR - =nonexistent,
|
||
.BR 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.
|
||
.TP
|
||
.B ic1234
|
||
Like NGC references, but from the Index Catalog.
|
||
.TP
|
||
.B 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.
|
||
.TP
|
||
.B m4
|
||
Catalog number 4 in Messier's catalog.
|
||
The output is the NGC number.
|
||
.TP
|
||
.B 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.
|
||
.TP
|
||
.B 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.
|
||
.TP
|
||
\fL"α umi"\fP
|
||
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.
|
||
.BR 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.
|
||
.TP
|
||
.B 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.
|
||
.TP
|
||
.B umi
|
||
All the patches in the named constellation.
|
||
.TP
|
||
.B mars
|
||
The planets are identified by their names.
|
||
The names
|
||
.B shadow
|
||
and
|
||
.B comet
|
||
refer to the earth's penumbra at lunar distance and the comet installed in the current
|
||
.IR astro (7).
|
||
The output is the planet's name, right ascension and declination, azimuth and altitude, and phase
|
||
for the moon and sun, as shown by
|
||
.BR astro .
|
||
The positions are current at the start of
|
||
.I scat 's
|
||
execution; see the
|
||
.B astro
|
||
command in the next section for more information.
|
||
.PP
|
||
The commands are:
|
||
.TF print
|
||
.TP
|
||
.BI add " item"
|
||
Add the named item to the set.
|
||
.TP
|
||
.BI keep " class ..."
|
||
Flatten the set and cull it, keeping only the specified classes.
|
||
The classes may be specific NGC types,
|
||
all stars
|
||
.RB ( sao ),
|
||
all NGC objects
|
||
.RB ( ngc ),
|
||
all M objects
|
||
.RB ( m ),
|
||
all Abell clusters
|
||
.RB ( abell ),
|
||
or a specified brightness range.
|
||
Brightness ranges are specified by a leading
|
||
.B >
|
||
or
|
||
.B <
|
||
followed by a magnitude.
|
||
Remember that brighter objects have lesser magnitudes.
|
||
.TP
|
||
.BI drop " class ..."
|
||
Complement to
|
||
.BR keep .
|
||
.TP
|
||
.BI flat
|
||
Some items such as patches represents sets of items.
|
||
.I Flat
|
||
flattens the set so
|
||
.I scat
|
||
holds all the information available for the objects in the set.
|
||
.TP
|
||
.BI print
|
||
Print the contents of the set. If the information seems meager, try
|
||
flattening the set.
|
||
.TP
|
||
.BI expand " n"
|
||
Flatten the set,
|
||
expand the area of the sky covered by the set to be
|
||
.I n
|
||
degrees wider, and collect all the objects in that area.
|
||
If
|
||
.I n
|
||
is zero,
|
||
.I expand
|
||
collects all objects in the patches that cover the current set.
|
||
.TP
|
||
.BI astro " option"
|
||
Run
|
||
.IR astro (7)
|
||
with the specified
|
||
.I options
|
||
(to which will be appended
|
||
.BR -p ),
|
||
to discover the positions of the planets.
|
||
.BR Astro 's
|
||
.B -d
|
||
and
|
||
.B -l
|
||
options can be used to set the time and place; by default, it's right now at the coordinates in
|
||
.BR /lib/sky/here .
|
||
Running
|
||
.B astro
|
||
does not change the positions of planets already in the display set,
|
||
so
|
||
.B astro
|
||
may be run multiple times, executing e.g.
|
||
.B "add mars"
|
||
each time, to plot a series of planetary positions.
|
||
.TP
|
||
.BI 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,
|
||
.I scat
|
||
does not have the information necessary to show the correct orientation for galaxies.
|
||
.IP
|
||
The option
|
||
.B nogrid
|
||
suppresses the lines of declination and right ascension.
|
||
By default,
|
||
.I scat
|
||
labels NGC objects, Abell clusters, and bright stars; option
|
||
.B nolabel
|
||
suppresses these while
|
||
.B alllabel
|
||
labels stars with their SAO number as well.
|
||
The default size is 512×512; options
|
||
.B dx
|
||
.I n
|
||
and
|
||
.BR dy
|
||
.I n
|
||
set the
|
||
.I x
|
||
and
|
||
.I y
|
||
extent.
|
||
The option
|
||
.B zenithup
|
||
orients the map so it appears as it would in the sky at the time and
|
||
location used by the
|
||
.B astro
|
||
command
|
||
.RI ( q.v. ).
|
||
.IP
|
||
The output is designed to look best on an LCD display.
|
||
CRTs have trouble with the thin, grey lines and dim stars.
|
||
The option
|
||
.B nogrey
|
||
uses white instead of grey for these details, improving visibility
|
||
at the cost of legibility when plotting on CRTs.
|
||
.TP
|
||
.B "plate \f1[[\f2ra dec\f1] \f2rasize\f1 [\f2decsize\f1]]"
|
||
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
|
||
.B 9fs
|
||
.B juke
|
||
before running
|
||
.IR scat .
|
||
.TP
|
||
.BI 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.
|
||
.I Scat
|
||
does not change the hardware color map, which
|
||
should be set externally to a grey scale; try the command
|
||
.B getmap gamma
|
||
(see
|
||
.IR colors (1))
|
||
on an 8-bit color-mapped display.
|
||
.PD
|
||
.SH EXAMPLES
|
||
Plot the Messier objects and naked-eye stars in Orion.
|
||
.EX
|
||
ori
|
||
keep m <6
|
||
plot nogrid
|
||
.EE
|
||
.PP
|
||
Draw a finder chart for Uranus:
|
||
.EX
|
||
uranus
|
||
expand 5
|
||
plot
|
||
.EE
|
||
.PP
|
||
Show a partial lunar eclipse:
|
||
.EX
|
||
astro -d
|
||
2000 07 16 12 45
|
||
moon
|
||
add shadow
|
||
expand 2
|
||
plot
|
||
.EE
|
||
.PP
|
||
Draw a map of the Pleiades.
|
||
.EX
|
||
"alcyone"
|
||
expand 1
|
||
plot
|
||
.EE
|
||
.PP
|
||
Show a pretty galaxy.
|
||
.EX
|
||
ngc1300
|
||
plate 10'
|
||
.EE
|
||
.SH FILES
|
||
.B /lib/sky/*.scat
|
||
.SH SOURCE
|
||
.B /sys/src/cmd/scat
|
||
.SH SEE ALSO
|
||
.IR astro (7)
|
||
.br
|
||
.B /lib/sky/constelnames\ \
|
||
the three-letter abbreviations of the constellation names.
|
||
.PP
|
||
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.
|