[ 156 ] 

 XXV. Intelligence and Miscellaneous Articles. 



ON A SIMPLE OCULAR-SPECTROSCOPE FOR STARS. 

 BY F. ZOLLNER. 



rPHE annexed figure shows, of the natural size, the section of a 

 -*- compendious form of star-spectroscope in combination with 

 the ocular of a telescope. 



It consists of a small direct-vision prism fixed in a tube C D, the 

 dispersion of which is about 

 equivalent to that of the sys- 

 tem of prisms of a Browning 

 miniature spectroscope. The 

 tube CD is movable in a se- 

 cond tube, AB, which can be 

 screwed upon the head of the 

 eyepiece and contains a cylin- 

 drical lens L of about 100 

 milliins. focal distance. As 

 the length of the line of light- 

 produced by this lens depends both on its focal distance and also 

 on the dimensions and proportions of the optical parts of the tele- 

 scope, it is advisable to have in readiness several cylindrical lenses 

 ol different lengths of focus, so as to be able to employ them ac- 

 cording to the length of the line of light (and consequently the 

 breadth of the spectrum) desired. 



1 and 0„ are the two lenses of the eyepiece, and hence do not 

 belong to the spectroscope. 



If with this instrument the spectrum of a star is to be observed, 

 the tube C D with the prism is first removed, and the ocular so ar- 

 ranged that when the eye is at a sharp line of light is seen. It 

 is essential, in doing this, that the eye should be at about the same 

 distance from the lens L as w T hen the prism is employed. The 

 tube C D is now inserted, in such a manner that the refracting 

 edge of the prism lies, as usual, parallel to the luminous line, and 

 consequently the spectrum attains its greatest breadth. Self -evi- 

 dently, for a given telescope, the suitable arrangement need only 

 be once ascertained ; so that then by a small screw S the prism can 

 be fixed in an invariable position with respect to the cylindrical 

 lens L. The prism is manufactured by M. Merz, of Munich ; and 

 he prefers to use it in this compendious form for microscopes. 



The intensity of the light of this ocular-spectroscope is so consi- 

 derable, that, in combination with a small portable telescope, the 

 objective of which has only 35 millimetres aperture and about 400 

 millims. focal distance, it shows distinctly the lines of stars of the 

 first magnitude, such as "Wega, a Orionis, and even a Herculis ivheu 

 the state of the atmosphere corresponds, as Professor "Winnecke and 

 Dr. Yogel convinced themselves and others on the occasion of their 

 visit to Leipzig in the course of the past year. When Yenus ap- 

 pears as a slender crescent, its spectrum is singularly beautiful. 



Although, according to the well-known methods employed by 



