STARCHART

NAME

SYNOPSIS

DESCRIPTION

Star data is optionally overlayed with other cosmic objects, such as planets. If limiting magnitudes are properly set and the Messier database is available, Messier objects and some NGC objects are also printed.

The starchart center is specified by two parameters: Right Ascension [0.00 to 24.00 hours] and Declination [-90.00 to +90.00 degrees]. An optional third parameter defines the N/S range of the output window, in degrees of declination. Digits after decimal point are taken as minutes: object positions can therefore be taken directly from a star catalog.

An optional fourth parameter gives a title. This conforms to the 'old' Yale star chart format. Two new parameters can be added after title, defining the magnitude limit and label printing magnitude limit. These are discussed below. All parameters can be given by using options, which offers more flexibility. Parameters are:

-r

Right ascension.

-d

Declination.

-s

Scale.

-t

Title. All these work as described above. Additional switches:

-m

Star limiting magnitude. This sets limits on the faintest stars displayed on the ``master'' view. Default limits are device driver dependent (more below). The ``thumbnail'' finder view is set to a related limit.

-l

Label limiting magnitude. The new Yale database contains both a small set of familiar names (for stars and special objects), plus an extensive list of labels (Greek Bayer letter or Flamsteed numbers). Star names (including planet names) always print for this small set. To avoid clutter, the labels may be omitted below a cut-off magnitude by specifying this value.

-g

Greek/Flamsteed annotation magnitude. Labels printed for stars dimmer than this value will use a Bayer or numerical label in favor of a proper name. The default (2.05) includes nearly all well-known proper names including Polaris, and excludes but a small number (such as Algol). Large values generate charts full of obscure Arabian names, small (zero or negative) values produce non-verbose charts, eg. ``a'', in Greek where possible, instead of ``Sirius''.

-c

A three or four character mnemonic follows, which is a search string for a matching line-item entry in the file con.locs. If found, then the initial values for Ra, Decl, Scale and Title are taken from that file. Because the command line is parsed from left to right, subsequent switches might change the scale, title, or otherwise fine-tune the new defaults.

-f

A list of files follow, each containing ephemerides in the .star format, which will overlay the output. This is also useful for generating constellation boundaries, Milky Way isophots, and planet or satellite tracks. (The .star format additionally includes records for vector and text annotation). Files are processed sequentially. Thus, order may take on meaning for devices which provide a 2-1/2D page description, such as PostScript.

-b

This switch provides a single full-page of output, without a thumbnail-sized finder chart. The legend placard is replaced with a single line banner giving title, right ascension, declination and limiting magnitude. This mode is useful for the construction of atlas pages. Because the page depicts the same vertical scale in degrees of declination, the output will cover a slightly reduced extent in right ascention.

-a

This switch provides annotation-only (text) output: all stars and non-stellar objects are omitted (including objects normally rendered by using alpha characters). Borders and legends are left undisturbed. This feature is useful in separating output detail, as when making (color) overhead transparencies.

-o

This switch provides object-only output, and is the complement of the above switch. When both switches appear together, all output is displayed. This resembles the default case (neither switch), except in that case object and annotation detail are written together. Here the software makes two consecutive passes through all datasets and arranges output detail to be written with all cosmic objects prefacing all related text annotations. This is useful in providing data for PostScript files in which rendering happens in a 2-1/2D back-to-front order, thus providing for a cleaner overlaying of output.

-y -w -p

These switches allow for the redefinition of the files yale.star, messier.star and planet.star, respectively.

OUTPUT

Objects are drawn in glyphs defined by each display driver. Vector-only devices rely on the parent module ``starimages.c'' to provide shape tables; other devices plot special characters (stardsp or starpic) or private symbols (PostScript). The latter additionally provides distinctions between object subclasses, e.g. planetary vs diffuse nebula. The code provides for this generally, creation of new glyphs.

Sanson's sinusoidal projection is used to map coordinates. This projection preserves both area and linearity in Declination (y axis). It gives good conformality (angle correctness) near the equator, so it is useful along the Ecliptic. Lines of RA converge at the poles (unlike cylindrical projections), though Cassiopeia and the Dipper reproduce well.  

EXAMPLES

# Sagittarius: a nice bunch of Messier objects.
starpost -c sgr -a -o -t Sagittarius >sag.ps

# Orion: the belt lies near 5h40m in RA, just below the CE.
stardsp 5.32 -5 12 "Trapezium (Orion)" 8 5 | more

FILES

planet.star     Planets (optional)
con.locs        default mnemonic locations

These default paths can be easily changed in the Makefile.  

BUGS

If <minutes> part of the parameters is greater than 59 it is silently truncated to 59.

All .star file coordinates are for epoch E2000.0. The Messier objects in messier.star were taken from precessed E1975.0 data. The additional NGC objects were taken from data in the star atlas by Norton and precessed from E1950.0. Descriptions and accurate magnitude values of all Messier objects were taken from the 1988 edition of the Royal Astronomical Society of Canada (RASC) handbook.  

FUTURE EXTENTIONS

AUTHOR/EDITOR

MAJOR CONTRIBUTORS

Index

NAME

SYNOPSIS

DESCRIPTION

OUTPUT

EXAMPLES

FILES

BUGS

FUTURE EXTENTIONS

AUTHOR/EDITOR

MAJOR CONTRIBUTORS