plot2sky: Draws a sky plot
plot2sky draws plots on the celestial sphere.
This can be represented in a number of ways, controlled by the
projection parameter; by default the view is of a rotatable
sphere seen from the outside
(which approximates to a tangent projection for small regions of the sky),
but Hammer-Aitoff and Plate Carée projections are also available.
A number of options are also provided for drawing and labelling the
grid showing celestial coordinates.
Positional coordinates are specified as lon, lat
pairs giving longitude and latitude in decimal degrees.
By default these are represented in the output in the same, unlabelled,
coordinate system.
However the command can can also transform between different coordinate
systems if you specify the data and view systems e.g.:
plot2sky viewsys=galactic
layer1=mark in1=cat.fits lon1=RA2000 lat1=DEC2000 datasys1=equatorial
Content is added to the plot by specifying
one or more plot layers using the
layerN parameter.
The N part is a suffix applied to
all the parameters affecting a given layer;
any suffix (including the empty string) may be used.
Available layers for this plot type are:
mark,
size,
sizexy,
skyvector,
skyellipse,
skycorr,
link2,
mark2,
poly4,
mark4,
polygon,
area,
central,
label,
arealabel,
contour,
skydensity,
healpix,
skygrid.