Heliographic Coordinates

Heliographic Coordinates

 

heliographic latitude and longitude, magnitudes used to determine positions of points on the surface of the sun. The heliographic latitude is the angular distance of a given point from the solar equator measured along a solar meridian. Heliographic longitude is the angle between the plane of the meridian of a given point and the plane of the zero meridian, taken to be the so-called Carrington meridian, which crosses the ascending node of the solar equator at the mean Greenwich noon of Jan. 1, 1854. Astronomical almanacs give for each day the data (the heliographic coordinates of the apparent center of the sun, the orientation of its axis of rotation), needed to determine the heliographic coordinates of any point on the surface of the sun.

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I've been trying to locate (without success) a program which will calculate and depict the heliographic coordinates for the sun for any given date and time, in order to allow me to plot sunspots.
Not only is this technique very convenient and eminently safe, it is also the most reliable way to obtain the heliographic coordinates of sunspots with precision.