Ai'c.rsT, 1904.] 



KNOWLEDGE & SCIENTIEIC NEWS. 



177 



The •* Panorama " 



Military Telescope. 



1?V I)k. ALIKEU CiKAUKNU 1 I /. 



The field of view of a telescope is necessarily limited, 

 and whenever the observer wishes to inspect the w hole 

 of his horizon, lie is compelled to turn round his whole 

 instrument, while his body has to follow this rotation. 

 This drawback is obviated in the so-called 

 " panorama " telescope, where the desired range of 



"::1-4 — Q-9- 



Fig. I. 



vision is secured whilst the eye-piece part of the instru- 

 ment may remain immovable. It is obvious that the 

 necessary condition for practical use will be that, apart 

 from the magnification produced by the instrument, 

 the observer should receive the same impression of the 

 horizon as if he viewed it with the naked eye. If, 

 therefore, an ordinary telescope, either terrestrial or 

 astronomical, were arranged as represented in figures 

 I and 2, with a total reflection prism turning round its 



-1-^ — e-^ 



Fig. 2. 



vertical axis in front of the objective, in order to obtain 

 the panorama effect, the image produced would under- 

 go an angular distortion equal to the angle of rotation. 

 Anything placed on the top in figure i would, after a 

 I So" rotation of the reflection prism, appear to lie be- 

 low ; the image thus being turned also by iSo". 

 The prism combination to be chosen for the internal 

 optical construction of the panorama telescope had, 

 therefore, to fulfil the following conditions : — 



1. The image should be erected, simple astro- 

 nomical eye-pieces being used instead of the awk- 

 ward terrestrial eye-pieces. 



2. The image, whilst exploring the surrounding 

 horizon, should be kept in position, presenting itself 

 to the observer as it would appear to the naked eye 

 looking around. 



The Goerz firm has designed several types of 

 panorama telescopes, and the one described below was 

 especially intended to be used as a pointing telescope in 

 connection with guns. The optical elements of this 



I iiiiiiiiiKiinui ai e >lu)Wii ill liguic j, wlicie A i.-> a total 

 retlection prism, B the erecting prism, C the objective, 

 I) a prism separately represented in figure 4, and () an 

 astronomical eye-piece. 



The rays from the object, penetiating the prism A, 

 are deflected downwards into the prism U, erecting 

 them in one direction. After traversing the objective 

 C, the prism D will produce a lateral change as seen 

 from figiue 4. The image of the object is, therefore, 

 produced at the centre of the eye-piece diaphragm E, 

 in a position corresponding to reality, where it is viewed 

 through the astronomical cye-piecc in enlarged size. 



The prism B has a square cross section, an import- 

 ant feature being the fact that a rotation by iSo'' 

 around its longitudinal axis will result in the image 

 being turned by 36o''-, the image thus rotating at twice 

 the angular speed of the prism. In order, therefore, 

 to obtain an image corresponding to nature, the prism 

 H should be made to follow the movement of the prism 



Fig. i. 



\ at half its angular speed. To secure this effect, the 

 latter is inserted into the casing U, being fitted below 

 with a toothing and rigidly connected to the spiral 

 drum H. The latter may be made to rotate on the 

 box K, which is screwed inside to the casing V and 

 outside to the cap G. In the casing V rotates the 

 tube L, being also pro\ ided with a toothing at its 

 upper end, and bearing at the top the framing which 

 contains the prism B, and below the objective C. In 

 the two toothings the double pinion M engages, the 

 ratios of gearing being so designed as to impart to the 

 tube L an angular speed of the same direction as that 

 of the [)risni A and of half its value. 



By acting on a .screw .solidly mounted in the cap (i 

 arid engaging into the toothing J of the spiral drum II, 

 the reflection prism .4 and accordingly the prism B, are 

 turned round, thus producing in the field of view the 

 characteristic panorama effect. 



In the case of the panorama telescope being used 

 fiom a protected observing stand, the immovable [)osi- 



