368 



ERECT IMAGES IN DRAWINGS 



[CH. X 



POSITION OF THE OBJECT FOR ERECT IMAGES ON A HORIZONTAL 



SURFACE WITH AN OBJECTIVE OR WITH AN OBJECTIVE AND AN 



AMPLIFIER AND A 45 DEGREE MIRROR OR PRISM 



520. For an opaque horizontal screen. (A) If for a drawing 

 table and mirror (fig. 182), place the object on the stage so that 

 it faces the objective and is right edge up. The image on the 

 horizontal surface will appear erect when the observer looks at it 

 facing away from the light. 



The object on the stage will appear erect when the observer looks 

 at it facing toward the light. 



Fip 208. KEPLER'S METHOD OF PRODUCING ERECT IMAGES BY MEANS 

 OF Two PROJECTION LENSES. 



(From Scheiner's "Oculus" , 1619). 



