Plotting finding charts

CURSA contains the application catchart for plotting a basic finding chart showing objects selected from a catalogue which lie within in a given region of the sky. catchart plots equatorial coordinates using the tangent plane projection conventional in optical astronomy. This projection is described in standard textbooks on spherical astronomy (see, for example, Spherical Astronomy by R.M. Green[15]).

catcoord plots target lists (see Section ). It will plot either a single target list or superimpose several target lists on a single finding chart.

All that can be guaranteed about a target list is that it contains columns defining the coordinates of the objects. Therefore, by default, catcoord plots all the objects in the list using the same default plotting symbol (circle, square etc), drawn to the same size in the same colour. However, it is often desirable to plot the objects with a specified symbol and colour and the size of the symbol varying with some property of the object (traditionally magnitude). The application catchartrn allows extra columns to be added to the target list which prescribe how each object is to be plotted.

Thus, a simple, default finding chart can be produced by running catchart on any target list. However, the plot can be customised by running catchartrn, to specify how each object is to be plotted, prior to running catchart. The next section () suggests some catalogues which might be suitable for producing finding charts, the subsequent one () describes how to run catchart and the following one () how to customise the plot. The final section () gives a complete worked example.