pro calculate_emission_angles,planet,pl_center,polar_r_versus_equat_r,norm_ring_plane,em_angles_rad

	;create a 3d_planet(n_pixels_x(planet),n_pixels_y(planet),3)
	;with 3d vectors of half-ellipse
	@~\lightning\idl\iss\scattered_light\get_three_d_planet.pro

	sz=size(planet)
	nx=sz(1)
	ny=sz(2)
	em_angles_rad=planet*0.
	for ix=0,nx-1 do begin
	for iy=0,ny-1 do begin
		;r_xy=float([ix,iy]-pl_center)
		r=transpose(three_d_planet(ix,iy,0:2))
		if (norm(r) ne 0.) then begin
			norm_planet=transpose(three_d_planet(ix,iy,3:5))
			r_xy_norm_abs=(norm_planet(0)^2+norm_planet(1)^2)^.5
			em_angles_rad(ix,iy)=asin(r_xy_norm_abs)
		endif
	endfor
	endfor
	;erase
	;tvscl,em_angles_rad,15
	;print,em_angles_rad(nx/2,*)
end