336 lines
8.7 KiB
Plaintext
336 lines
8.7 KiB
Plaintext
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.TH SCAT 7
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.SH NAME
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scat \- sky catalogue and Digitized Sky Survey
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.SH SYNOPSIS
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.B scat
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.SH DESCRIPTION
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.I Scat
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looks up items in catalogues of objects
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outside the solar system
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and implements database-like manipulations
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on sets of such objects.
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It also provides an interface to
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.IR astro (7)
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to plot the locations of solar system objects.
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Finally, it displays images from the
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Space Telescope Science Institute's
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Digitized Sky Survey, keyed to the catalogues.
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.PP
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Items are read, one per line, from the standard input
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and looked up in the catalogs.
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Input is case-insensitive.
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The result of the lookup becomes the set of objects available
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to the database commands.
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After each lookup or command, if more than two objects are
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in the set,
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.I scat
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prints how many objects are in the set; otherwise it
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prints the objects'
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descriptions or cross-index listings (suitable for input to
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.IR scat ).
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An item is in one of the following formats:
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.TP
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.B ngc1234
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Number 1234 in the New General Catalogue of
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Nonstellar Objects, NGC2000.0.
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The output identifies the type
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.RB( Gx =galaxy,
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.BR Pl =planetary
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nebula,
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.BR OC =open
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cluster,
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.BR Gb =globular
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cluster,
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.BR Nb =bright
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nebula,
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.BR C+N =cluster
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associated with nebulosity,
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.BR Ast =asterism,
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.BR Kt =knot
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or nebulous region in a galaxy,
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.BR *** =triple
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star,
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.BR D* =double
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star,
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.BR ? =uncertain,
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.BR - =nonexistent,
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.BR PD =plate
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defect, and
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(blank)=unverified or unknown),
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its position in 2000.0 coordinates,
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its size in minutes of arc, a brief description, and popular names.
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.TP
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.B ic1234
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Like NGC references, but from the Index Catalog.
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.TP
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.B sao12345
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Number 12345 in the Smithsonian Astrophysical Star Catalogue.
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Output identifies the visual and photographic magnitudes,
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2000.0 coordinates, proper motion, spectral type, multiplicity and variability
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class, and HD number.
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.TP
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.B m4
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Catalog number 4 in Messier's catalog.
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The output is the NGC number.
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.TP
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.B abell1701
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Catalog number 1701 in the Abell and Zwicky
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catalog of clusters of galaxies.
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Output identifies the magnitude of the tenth brightest member of the cluster,
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radius of the cluster in degrees, its distance in megaparsecs,
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2000.0 coordinates, galactic latitude and longitude,
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magnitude range of the cluster (the `distance group'),
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number of members (the `richness group'), population
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per square degree, and popular names.
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.TP
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.B planetarynebula
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The set of NGC objects of the specified type.
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The type may be a compact NGC code or a full name, as above, with no blank.
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.TP
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\fL"α umi"\fP
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Names are provided in double quotes.
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Known names are the Greek
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letter designations, proper names such as Betelgeuse, bright variable stars,
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and some proper names of stars, NGC objects, and Abell clusters.
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Greek letters may be spelled out, e.g.
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.BR alpha .
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Constellation names must be the three-letter abbreviations.
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The output
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is the SAO number.
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For non-Greek names, catalog numbers and names are listed for all objects with
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names for which the given name is a prefix.
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.TP
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.B 12h34m -16
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Coordinates in the sky are translated to the nearest `patch',
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approximately one square degree of sky.
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The output is the coordinates identifying the patch,
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the constellations touching the patch, and the Abell, NGC, and SAO
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objects in the patch.
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The program prints sky positions in several formats corresponding
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to different precisions; any output format is understood as input.
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.TP
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.B umi
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All the patches in the named constellation.
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.TP
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.B mars
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The planets are identified by their names.
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The names
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.B shadow
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and
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.B comet
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refer to the earth's penumbra at lunar distance and the comet installed in the current
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.IR astro (7).
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The output is the planet's name, right ascension and declination, azimuth and altitude, and phase
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for the moon and sun, as shown by
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.BR astro .
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The positions are current at the start of
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.I scat 's
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execution; see the
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.B astro
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command in the next section for more information.
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.PP
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The commands are:
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.TF print
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.TP
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.BI add " item"
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Add the named item to the set.
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.TP
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.BI keep " class ..."
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Flatten the set and cull it, keeping only the specified classes.
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The classes may be specific NGC types,
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all stars
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.RB ( sao ),
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all NGC objects
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.RB ( ngc ),
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all M objects
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.RB ( m ),
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all Abell clusters
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.RB ( abell ),
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or a specified brightness range.
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Brightness ranges are specified by a leading
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.B >
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or
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.B <
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followed by a magnitude.
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Remember that brighter objects have lesser magnitudes.
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.TP
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.BI drop " class ..."
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Complement to
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.BR keep .
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.TP
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.BI flat
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Some items such as patches represents sets of items.
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.I Flat
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flattens the set so
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.I scat
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holds all the information available for the objects in the set.
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.TP
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.BI print
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Print the contents of the set. If the information seems meager, try
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flattening the set.
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.TP
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.BI expand " n"
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Flatten the set,
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expand the area of the sky covered by the set to be
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.I n
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degrees wider, and collect all the objects in that area.
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If
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.I n
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is zero,
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.I expand
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collects all objects in the patches that cover the current set.
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.TP
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.BI astro " option"
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Run
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.IR astro (7)
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with the specified
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.I options
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(to which will be appended
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.BR -p ),
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to discover the positions of the planets.
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.BR Astro 's
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.B -d
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and
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.B -l
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options can be used to set the time and place; by default, it's right now at the coordinates in
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.BR /lib/sky/here .
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Running
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.B astro
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does not change the positions of planets already in the display set,
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so
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.B astro
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may be run multiple times, executing e.g.
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.B "add mars"
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each time, to plot a series of planetary positions.
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.TP
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.BI plot " option"
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Expand and plot the set in a new window on the screen.
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Symbols for NGC objects are as in Sky Atlas 2000.0, except that open clusters
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are shown as stippled disks rather than circles.
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Abell clusters are plotted as a triangle of ellipses.
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The planets are drawn as disks of representative color with the first letter of the name
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in the disk (lower case for inferior planets; upper case for superior);
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the sun, moon, and earth's shadow are unlabeled disks.
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Objects larger than a few pixels are plotted to scale; however,
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.I scat
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does not have the information necessary to show the correct orientation for galaxies.
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.IP
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The option
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.B nogrid
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suppresses the lines of declination and right ascension.
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By default,
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.I scat
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labels NGC objects, Abell clusters, and bright stars; option
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.B nolabel
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suppresses these while
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.B alllabel
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labels stars with their SAO number as well.
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The default size is 512×512; options
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.B dx
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.I n
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and
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.BR dy
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.I n
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set the
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.I x
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and
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.I y
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extent.
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The option
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.B zenithup
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orients the map so it appears as it would in the sky at the time and
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location used by the
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.B astro
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command
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.RI ( q.v. ).
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.IP
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The output is designed to look best on an LCD display.
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CRTs have trouble with the thin, grey lines and dim stars.
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The option
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.B nogrey
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uses white instead of grey for these details, improving visibility
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at the cost of legibility when plotting on CRTs.
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.TP
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.B "plate \f1[[\f2ra dec\f1] \f2rasize\f1 [\f2decsize\f1]]"
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Display the section of the Digitized Sky Survey (plate scale
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approximately 1.7 arcseconds per pixel) centered on the
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given right ascension and declination or, if no position is specified, the
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current set of objects. The maximum area that will be displayed
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is one degree on a side. The horizontal and vertical sizes may
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be specified in the usual notation for angles.
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If the second size is omitted, a square region is displayed.
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If no size is specified, the size is sufficient to display the centers
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of all the
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objects in the current set. If a single object is in the set, the
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500×500 pixel block from the survey containing the center
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of the object is displayed.
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The survey is stored in the CD-ROM juke box; run
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.B 9fs
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.B juke
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before running
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.IR scat .
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.TP
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.BI gamma " value"
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Set the gamma for converting plates to images. Default is \-1.0.
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Negative values display white stars, positive black.
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The images look best on displays with depth 8 or greater.
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.I Scat
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does not change the hardware color map, which
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should be set externally to a grey scale; try the command
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.B getmap gamma
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(see
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.IR getmap (9.1))
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on an 8-bit color-mapped display.
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.PD
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.SH EXAMPLES
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Plot the Messier objects and naked-eye stars in Orion.
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.EX
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ori
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keep m <6
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plot nogrid
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.EE
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.PP
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Draw a finder chart for Uranus:
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.EX
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uranus
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expand 5
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plot
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.EE
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.PP
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Show a partial lunar eclipse:
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.EX
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astro -d
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2000 07 16 12 45
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moon
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add shadow
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expand 2
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plot
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.EE
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.PP
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Draw a map of the Pleiades.
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.EX
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"alcyone"
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expand 1
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plot
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.EE
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.PP
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Show a pretty galaxy.
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.EX
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ngc1300
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plate 10'
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.EE
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.SH FILES
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.B /lib/sky/*.scat
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.SH SOURCE
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.B /sys/src/cmd/scat
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.SH SEE ALSO
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.IR astro (7)
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.br
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.B /lib/sky/constelnames\ \
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the three-letter abbreviations of the constellation names.
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.PP
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The data was provided by the Astronomical Data Center at the NASA Goddard
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Space Flight Center, except for NGC2000.0, which is Copyright © 1988, Sky
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Publishing Corporation, used (but not distributed) by permission. The Digitized Sky Survey, 102
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CD-ROMs, is not distributed with the system.
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