File:Solar points.svg

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English: Geometry of the four solar points (solar point, subsolar point, anthelic point and antisolar point) on the celestial sphere.
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Author Syntex
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This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license.
You are free:
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Under the following conditions:
  • attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
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Other versions See File:Points solaires annotes simple.svg for an annotated version (in french) of this diagram
SVG development
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This vector image was created with Asymptote by dvisvgm.
Source code
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Asymptote code

// Draw the solar circles on the celestial sphere
import three;

// Figure sizes
real sx = 300;
real sy = sx;
triple figc = (sx/2,sy/2,0);  // center of figure
size(sx,sx);

// Projection
currentprojection = orthographic(5,4,2);

// Radius of celestial sphere
real rsk = sx/2;

// Pens
pen paxes1   = linetype("8 8"),
    paxes2   = linetype("4 4"),
    plinsol  = orange,
    pdotsol  = linewidth(6),
    pangle1  = heavycyan,
    pangle2  = heavyred;

// Horizon plane
draw((0,0,0)--(sx,0,0)--(sx,sy,0)--(0,sy,0)--cycle);
draw(circle(figc, rsk));

// Cardinal directions
//draw((sx/2,0,0)--(sx/2,sy,0), p=paxes1);  // East-West
draw((0,sy/2,0)--(sx/2,sy/2,0));  // North
//draw((sx/2,sy/2,0)--(sx,sy/2,0), p=paxes1);  // South
draw((figc+(0,0,-rsk))--(figc+(0,0,rsk))); // Zenith-Nadir

// Meridian
//draw(shift(figc)*rotate(90,X)*circle((0,0,0),rsk));


// Altazimutal Sun position
real az = 220;  // azimuth, degrees
real h  = 36;   // elevation, degrees

// Solar point (PS)
triple PS  = figc+rsk*dir(90-h, 180-az),
       PSh = figc+rsk*dir(90, 180-az);
dot(PS, p=plinsol+pdotsol);

// Subsolar point (PSS)
triple PSS = figc+rsk*dir(90+h, 180-az);
dot(PSS, p=plinsol+pdotsol);

// Antisolar point (PAS)
triple PAS = figc+rsk*dir(90+h, -az),
       PASh = figc+rsk*dir(90, -az);
dot(PAS, p=plinsol+pdotsol);

// Anthelic point (PA)
triple PA  = figc+rsk*dir(90-h, -az);
dot(PA, p=plinsol+pdotsol);

// Vertical solar circle
draw(shift(figc)*rotate(az-180,-Z)*rotate(90,X)*circle((0,0,0),rsk), p=plinsol);

draw(PAS--PS, p=plinsol);
draw(PA--PSS, p=plinsol);
draw(PASh--PSh, p=plinsol+paxes1);

// Parhelic circle
draw(shift(figc+(0,0,rsk*sin(radians(h))))*rotate(180-az, Z)*arc((0,0,0),rsk*cos(radians(h)), 90, 0, 90, 180, Z), p=plinsol);
draw(shift(figc+(0,0,rsk*sin(radians(h))))*rotate(180-az, Z)*arc((0,0,0),rsk*cos(radians(h)), 90, -180, 90, 0, Z), p=plinsol+paxes1);

// Subparhelic circle
draw(shift(figc+(0,0,-rsk*sin(radians(h))))*rotate(180-az, Z)*arc((0,0,0),rsk*cos(radians(h)), 90, 0, 90, 180, Z), p=plinsol);
draw(shift(figc+(0,0,-rsk*sin(radians(h))))*rotate(180-az, Z)*arc((0,0,0),rsk*cos(radians(h)), 90, -180, 90, 0, Z), p=plinsol+paxes1);

// Azimuth angle
draw(shift(figc)*arc((0,0,0), rsk/4, 90, 180, 90, 180-az), p=pangle1);
draw(shift(figc)*arc((0,0,0), rsk/4+6, 90, 180, 90, 180-az), p=pangle1);

// Elevation angles of PS and PSS
draw(shift(figc)*rotate(180-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3, 90, 0, 90, h), p=pangle2);
draw(shift(figc)*rotate(180-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3, 90, -h, 90, 0), p=pangle2+paxes2);
draw(shift(figc)*rotate(180-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3+3, 90, 0, 90, h), p=pangle2);
draw(shift(figc)*rotate(180-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3+3, 90, -h, 90, 0), p=pangle2+paxes2);

// Elevation angles of PA and PAS
draw(shift(figc)*rotate(-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3, 90, 0, 90, h), p=pangle2);
draw(shift(figc)*rotate(-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3, 90, -h, 90, 0), p=pangle2+paxes2);
draw(shift(figc)*rotate(-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3+3, 90, 0, 90, h), p=pangle2);
draw(shift(figc)*rotate(-az,Z)*rotate(90,X)*arc((0,0,0), rsk/3+3, 90, -h, 90, 0), p=pangle2+paxes2);

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Date/TimeThumbnailDimensionsUserComment
current13:44, 29 May 2013Thumbnail for version as of 13:44, 29 May 2013376 × 256 (8 KB)Syntex (talk | contribs)User created page with UploadWizard

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