Circle

This is a very simple region consisting of a single convex of one halfspace. For most users, a circular search area is best described by the center and radius rather than an offset of the cutting plane. The API has ways of creating Halfspaces like this, given the RA/DEC in degrees and the radius of circle expressed in arc minutes.
Picture of a halfspace
Figure 2. 3600 arc min wide halfspace

SPECIFICATION

CIRCLE J2000 0 90 1800

NORMAL FORM

REGION CONVEX 0 0 1 0.86602540378443871

C# Code snippet

using Spherical;
using Spherical.Htm;
/* .... */
namespace MySpace {
    public class MyApp {
        public void MyFunc(){
            Region r = new Region(new Convex(new Halfspace(0.0, 90.0, 1800)), false);
            /* ... */
        }
        public void MyAlternate(){
            Region r = new Region();
            Convex c = new Convex();
            Halfspace h = new Halfspace(0.0, 90.0, 1800);
            c.Add(h);
            r.Add(c);
        }
		public void MyAlternate2(){
			Region r = Parser.compile("CIRCLE J2000 0 90 1800");
		}
    }
}

Last update May 29, 2007 György Fekete version 3.1.2