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common to the two index mirrors, and the sighting telescope are mounted on an arm, which moves about the same axis as that of the lower index mirror. Thus the horizon mirror in all positions reflects the axis of the index mirror to the eye. If the horizon mirror is placed as far towards the zero end of the scale as it will go, this position will be found convenient for observing all angles up to about 70°, the rays from both objects passing to one side of the horizon mirror. For greater angles, the horizon mirror is turned through an angle less by about 20° than that estimated for the new angle, so that it avoids the paths of the observed rays, which now pass on different sides of the horizon mirror.

Each line of vision is reflected from its own index mirror and the horizon mirror, and the divergence of the lines of vision is measured by the angle between the two index mirrors. With this instrument the parallax possible is negligibly small.

The instrument is useful for use in open country and for roughly taking altitudes.

Wide Angle Pocket Sextant. Fig. 4.

9. Nautical Sextant. (Fig. 5.)

Brazed metal frame of triangle pattern giving increased rigidity. Arc 185 mm, radius divided on silver and reading by vernier to 10 seconds. Star telescope. Inverting telescope

Le texte affiché peut comporter un certain nombre d'erreurs. En effet, le mode texte de ce document a été généré de façon automatique par un programme de reconnaissance optique de caractères (OCR). Le taux de reconnaissance estimé pour cette page est de 99,46 %.

La langue de reconnaissance de l'OCR est l'Anglais.