Thanks for taking a look!


> Figure 1.3 , page 11
> 
>  From the point gamma on ICRF equator, starting sphere, the axis of 
> rotation of the planet is located at 90°+alpha, for an amount of 
> 90°-delta. (a single tilting of the planet axis, along a single 
> perpendicular axis)
> 
> If I assert +x is gamma at start, +z north, you have to apply a rotation 
> along v_rotate( y, alpha*z) of 90°-delta, then a rotation of W along the 
> new pole axis.
> 

I can't quite understand your steps. Do you want me to do this?

   #declare sphere_coo = vrotate(y, (90+alpha_0) * z);
   #declare sphere_coo = vrotate(sphere_coo, (90-delta_0) * x);

OTOH, I have attached my scene so far if you would please look at it. 
The result is not similar to what I see in the program Celestia for the 
same Julian day. (I have attached a screenshot of that program as well.)


Mike

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