![]() Meridian and parallel circles draw lines of length and height, respectively. Circle as well is a choice to pick a particular type. These serve to define grids to support orientation on a given custom star map. ![]() Compared to these, the local horizon appears to be variable because local time is part of its definition. For humans, three of these appear to be fix coordinate systems as they change only slowly due to sky mechanics: the equatorial, the ecliptical and the galactical one. Interpretation of object coordinates depends on their horizon type. Similar to Chart this element serves to define a horizon type, which is sort of a synonym for coordinate system. Furthermore, Chart defines the page dimensions of a custom star map and a viewport, which is a kind of passe-partout. Chart is of XSD type choice and serves to define the projection type, which in turn is a child of Chart. ![]() Actually, there is one more element above Chart but that’s essentially to group multiple chart definitions in a single file. This outermost piece of XML data starts a chart definition. Grid and comments are faint and small but not too much to make sure they're useful and readable. The example applies the major elements that make up a custom chart definition, namely charts, horizons, circles, dials, annotations and catalogs. A somewhat inaccurate element is the suggestion of the Milky Way, which nevertheless helps to orientate oneself in the night sky and not least is worth a mapping because of its mere extent. The focus of this custom chart is on the subject matter of giving precise information about the position of sky objects and their orientations with respect to different reference systems. The select expression restricts those to the first one.Īn application specific font provides the glyphs representing the different types of sky objects contained in the NGC 2000.0 catalog (for instance star, nebula, galaxy). Another criterion derives from the fact of the presence of multiple objects with identical common names in the supplementary file of the catalog. Object selection criterion is brightness, which restricts this map to objects with a mag value of 10 and below. It shows an azimuthal projection of objects from the NGC 2000.0 catalog as one probably can see on the northern hemisphere.
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