% cercles concentriques de déclinaison :
\foreach \d in {10, 20, ..., 60}
	\draw [gray](0,0) circle ({rayon(\d)}) ;
% cercle polaire :
\draw [gray, thick] (0,0) circle ({rayon(90-\eps)}) ;
%
% tropique Cancer :
\draw [gray, thick] (0,0) circle ({rayon(\eps)}) ;
%
% rayons d'AD  10 en 10 :
\foreach \ad in {10, 20, ..., 360}{
\draw [gray] (\ad:{rayon(70)}) -- (\ad:\requateur) ;
}
%
% pôle de l'écliptique :
\draw (0,{rayon(90-\eps)}) circle (0.15cm) ;
\draw (0,{rayon(90-\eps)}) circle (0.5cm) ;
%%%%%%%%%%%%%%%%%%%%%%%%%%
% méridien de la Polaire
%%%%%%%%%%%%%%%%%%%%%%%%%
\draw [gray, thin] ({180+38.38}:\requateur) -- ({38.38}:\requateur) node [above, sloped, pos=0.04, darkgray] {Mérid. de l'Étoile Polaire} node [above, sloped, pos=0.96, darkgray] {Mérid. de l'Étoile Polaire};
%
%%%%%%%%%%%%%%%%%%%%%%%%%%
%---------- Graduations radiales, déclinaison et distance polaire
%%%%%%%%%%%%%%%%%%%%%%%%%
% lignes des damiers :
\draw [very thin, gray] ({rayon(0)},0.60mm) -- ({rayon(70)},0.60mm) ;
\draw [very thin, gray] ({-rayon(0)},0.60mm) -- ({-rayon(70)},0.60mm) ;
\draw [very thin, gray] (-0.60mm, {rayon(0)}) -- (-0.60mm, {rayon(70)}) ;
\draw [very thin, gray] (0.60mm, {-rayon(0)}) -- (0.60mm, {-rayon(70)}) ;
	% damiers :
\foreach \ra in {0,2,...,67}{
\draw [darkgray,line width=0.60mm] ({rayon(\ra)},0.30mm) -- ({rayon(\ra+1)}, 0.30mm);
\draw [darkgray,line width=0.60mm] ({-rayon(\ra)},0.30mm) -- ({-rayon(\ra+1)}, 0.30mm);
\draw [darkgray,line width=0.60mm] (-0.30mm, {rayon(\ra)}) -- (-0.30mm, {rayon(\ra+1)});
\draw [darkgray,line width=0.60mm] (0.30mm, {-rayon(\ra)}) -- (0.30mm, {-rayon(\ra+1)});
}
	% chiffraisons déclinaison :
\foreach \c in {10,20,...,60}{
\draw (0:{rayon(\c)}) ++ (0,0.07) node[anchor=south, black, inner sep=0.2pt] {\c};
\draw (180:{rayon(\c)}) ++ (0,0.07) node[anchor=south, black, inner sep=0.2pt] {\c};
\draw (90:{rayon(\c)}) ++ (-0.07,0) node[anchor=east, black, inner sep=0.2pt] {\c};
}
%
	% chiffraisons distance polaire :
\foreach \c in {30,40,...,80}
\draw (-90:{rayon(90-\c)}) ++ (0.07,0) node[anchor=west, black, inner sep=0.2pt] {\c};