On the photogoniometric method of examining crystals with complex surfaces (II). Determining the spherical coordinates of poles of points on the photographs

Abstract The paper discusses methods of determining the spherical coordinates of the poles of reflections recorded on photographs obtained with the photogoniometric attachment, which is described in the first part of this paper, and examines the accuracy of the determined values as compared with the accuracy of the visual measurements with a two‐circle goniometer. One of the methods permits determination of (φ, ϱ) without making use of any measurements on the photographs obtained, viz. the reflection pattern of a portion of the surface recorded on the photograph is observed in the telescope‐microscope system of the goniometer, then some typical, easily recognizable points in it are selected and the (φ, ϱ) of their poles are determined through visual goniometric measurements, and after that these points are identified on the photographs and are marked there. It could be claimed that the accuracy of this method is equal to that of the visual measurements. The other method requires measurements of certain values on the photographs. The values measured are introduced in formulae for the particular type of camera used, from which the (φ, ϱ) are calculated. The accuracy of the method, the possible sources of systematic errors and some ways to eliminate them are considered.