The Astrophysical journal . Fig. 2 weredrawn. From these two curves it is possible to construct graph-ically the form of the diffraction pattern of the image of a sliteither bright on a dark background, or dark on a bright back-ground, either seen directly or through a prism ; provided onlythe slit is long in comparison with its width, which is the case ofall solar spectroscopes. The case where the slit is replaced bythe diffraction image of a star, as occurs in all stellar spectroscopesexcept the objective prism, I have not yet succeeded in reduc-ing to formulae which are practically applicab
The Astrophysical journal . Fig. 2 weredrawn. From these two curves it is possible to construct graph-ically the form of the diffraction pattern of the image of a sliteither bright on a dark background, or dark on a bright back-ground, either seen directly or through a prism ; provided onlythe slit is long in comparison with its width, which is the case ofall solar spectroscopes. The case where the slit is replaced bythe diffraction image of a star, as occurs in all stellar spectroscopesexcept the objective prism, I have not yet succeeded in reduc-ing to formulae which are practically applicable. In whatfollows I shall confine myself entirely to the case of circularaperture. The case of rectangular aperture is exactly thesame, it only being necessary to start with curve (i) in placeof curve (2). Case I.—A bright slit of angular width cr on a dark back-ground. This case has been treated analytically by Wadsworth and we have See previous footnote, also other papers by VVadsworth. EFFICIENCY OF SPECTROSCOPES 195. 6 6 ^ «b ^
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectspectru, bookyear1895
