Note 7 — THE ASTRONOMICAL MESSENGER
Edward Stafford Carlos translation
The line C H in Galileo’s figure represents the small pencil of rays from H which, after refraction through the telescope, reach the eye E. The enlarged figure shows that if O P be the radius of the aperture employed, the point H of the object would be just outside the field of view. The method, however, is at best only a very rough one, as the boundary of the field of view in this telescope is unavoidably indistinct.