Hadley, disclosed test for true figure, 27 John, real inventor of reflector, 25 Hadley’s reflector, tested with satisfactory results, 26 Hall, Chester Moor, designed first achromatic telescope, 27 had telescopes made as early as 1733, 27 Hand telescope, magnifying power, 150 monocular, 151 Hartmann test, 213 on large objectives, 267 principle of, 214 Hartness, turret telescope, 130, 131 Heliometer, principle of, 171 Hensoldt, prism form, 163 Herschel’s discovery of Uranus, 32 forty foot telescope, 34 Sir John, 35 Sir John, proposed defining condition, 81 Sir William, 31 Herschel’s time, instruments of, 35 Hevelius, construction for objective of 150 feet, 17 directions for designing Galilean and Keplerian telescopes, 14 invention of first periscope, 15 Johannes, 13 mention of advantage of plano convex lens, 14 mentions telescope due to DeRheita, 14 Housing reflector of 36 inch aperture, 243 rolling on track, 242 simplest instrument for fixed, 241 Huygens, Christian, devised methods of grinding & polishing, 16 Huygens’ eyepiece, introduction of, 24 Huygens, sketch of Mars, 16 I Image, correct extra focal, 208 critical examination of, 204 Image, curvature of, 87 seen without eyepiece, 134 showing unsymmetrical coloring, 208 Interference rings, eccentric, 205 Irradiation, 262 J Jansen, Zacharius, 4 K Kellner, ocular, 145 Kepler, astronomical telescope, 10 differences of from Galilean form, 10 Knife edge test of parabolic mirror, 212 L Lacquer, endurance of coating, 223 Latitude scale, 232 Lenses, determinate forms for, 80 Lens, magnifying power of, 134 “crossed,” 24 polishing the fine ground, 70 power of, 78 triple cemented, a useful ocular, 138 simple achromatic, 137 single, has small field, 137 spotted, cleaning of, 217 Light grasp and resolving power, 265 small telescope fails in, 264 Light ratio of star magnitudes, 264 Light transmitted by glass, 53 Lippershey, Jan, 2 discovery, when made, 5 retainer to, 3 Lunette à Napoleon Troisiéme, 154, 155, 162 M Magnifying power, directly as ratio of increase in tangent, 135 powers, increase of, 273 Marius, Simon, 5 used with glasses from spectacles, 5 Marius, picked up satellites of Jupiter, 5 Meridian photometer, 194 Metius, James, 4 Metius, tale of, 4 Micrometer, double image, 171 square bar, 171 Micrometers, 168 Micrometry, foundations of, 12 Mirror’s, aberrations of, 92 adjustment of, 206 concave spherical, 92 final burnishing of, 226 hyperboloidal, 96 lacquer coating for surface, 221 mounting, by Browning, 49 parabolic oblique, shows aberration, 95 surface, prevention of injury to, 220 Mittenzwey ocular, 141 Mountain stations, good or very bad, 254