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在天球上画出赤经和赤纬

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在天球上画出赤经和赤纬

我正在尝试绘制天球，但不知道如何在球体的外表面上绘制弧线。我想从春分点开始向太阳正下方赤道平面边缘绘制一个红色箭头。此外，我还想绘制赤纬，即从天球右侧向太阳位置绘制的弧线。这两条弧线都是用我精湛的 Photoshop 技巧绘制的。绘制赤经和赤纬的任意值的方法是什么？

天球

这是一个 MWE

\documentclass{scrartcl}
\usepackage{tikz}
\begin{document}
    \begin{tikzpicture}[
        dot/.style = {outer sep = 0, inner sep = 0, shape = circle, label = {#1}},
        dot/.default =,
        small dot/.style = {minimum size = .2cm, dot = {#1}},
        small dot/.default =,]
        % Equator
        \draw[thick] (-6,0) arc (180:360:6cm and 1cm);
        \draw[thick, dashed, opacity=.6] (-6,0) arc (180:0:6cm and 1cm);
        % Ecliptic of the sun (back)
        \draw[thick, dashed, rotate=23.5, color=blue, opacity=.6] (-6,0) arc (180:0:6cm and 1cm);
        % Celestial sphere
        \draw[thick] (0,0) circle (6cm);
        \shade[ball color=blue!10!white,opacity=0.20] (0,0) circle (6cm);
        % Earth
        \draw[thick] (0,0) circle (0.5cm);
        \shade[ball color=blue!60!white,opacity=0.80] (0,0) circle (0.5cm);
        % Sun
        \draw[thick] (5.5024,2.392) circle (0.5cm);
        \shade[ball color=yellow!60!white,opacity=0.8] (5.5024,2.392) circle (0.5cm);
        % Ecliptic of the sun (front)
        \draw[thick, rotate=23.5, color=blue] (-6,0) arc (180:360:6cm and 1cm);
        % Vernal equinox
        \node[fill = black, draw = black, small dot = {right: }] at (0.2,-1) {};
    \end{tikzpicture}
\end{document}

答案1

您可以使用已有的信息并借助 来绘制箭头arc。

输出

示例图片

代码

\documentclass{scrartcl}
\usepackage{tikz}

\usetikzlibrary{bending}
\begin{document}
    \begin{tikzpicture}[
        dot/.style = {outer sep = 0, inner sep = 0, shape = circle, label = {#1}},
        dot/.default =,
        small dot/.style = {minimum size = .2cm, dot = {#1}},
        small dot/.default =,]
        % Equator
        \draw[thick] (-6,0) arc (180:360:6cm and 1cm);
        \draw[thick, dashed, opacity=.6] (-6,0) arc (180:0:6cm and 1cm);
        % Ecliptic of the sun (back)
        \draw[thick, dashed, rotate=23.5, color=blue, opacity=.6] (-6,0) arc (180:0:6cm and 1cm);
        % Celestial sphere
        \draw[thick] (0,0) circle (6cm);
        \shade[ball color=blue!10!white,opacity=0.20] (0,0) circle (6cm);
        % Earth
        \draw[thick] (0,0) circle (0.5cm);
        \shade[ball color=blue!60!white,opacity=0.80] (0,0) circle (0.5cm);
        % Sun
        \draw[thick] (5.5024,2.392) circle (0.5cm);
        \shade[ball color=yellow!60!white,opacity=0.8] (5.5024,2.392) circle (0.5cm);
        % Ecliptic of the sun (front)
        \draw[thick, rotate=23.5, color=blue] (-6,0) arc (180:360:6cm and 1cm);
        % Vernal equinox
        \node[fill = black, draw = black, small dot = {right: }] at (0.2,-1) {};


        \draw[red, very thick, ->] (.2,-1) arc (-90:0:5.8 and 1.02);
        \draw[green, very thick, ->] ++(6cm,0) arc (0:23:6cm);
    \end{tikzpicture}
\end{document}

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