Chapter VII: Field glasses and telescopes

Reflection 98
Refraction 98
Lenses 98
Focus 99
Optical center 99
Image 99
Conjugate foci 99
Law of foci 100
Formation of image 101
Spherical aberration 102
Chromatic aberration 102
Telescopes 104
Galilean field glasses and telescopes 106
Porro prism field glasses and telescopes 106
Field glasses 108
Properties of telescopes and field glasses 109
Power 109
Light 111
Field 114
Definition 115
Field glasses and telescopes issued by the Signal Corps 119
Type A 121
Type B 124
Type C 125
Type D 125
Field-glass specifications 126