No text, but a visual code

[Antonio García Jiménez]

The image on f88 of the Tratado de Astrologia is not confusing.The equinox line is drawn: the intersection of the celestial equator with the ecliptic. At the Earth's equator the pole star is on the horizon, latitude 0º. The stars in f88 appear to come out of both poles, which are drawn as tubes. Note the difference with de axis above which is rectangular. It is the same idea of tubes that we see in the Rosette of the VM.
  The text of the Tratado de Astrologia reproduced by aStobbart talk about the city of Arim in the equatorial line, the place where the hours of the day are the same as those of the night.
Arin (or Arim, Arym) is the center of the world at equal distance from North, South, East and West. Latitude 0º, longitude 0º.
   The Arabs took the concept of the Indians and called it Qubbat al-Arin, dome of the world. Western science picked up the idea of the Arabs and incorporated it into their Geography and Cosmography.  Roger Bacon was one of the first to talk about Arin, and Pierre D'Ailly did it in his Imago Mundi, a contemporary work of Voynich. 
  I believe that the city drawn on the Rosette folio of the VM represents Arin. Obviously, the author drew a western city that he knew well.