Untersuchungen der inneren Struktur interstellarer Wolken. I. Photographisch‐photometrische Methode

For investigation of the inner structure of interstellar clouds with aid of the photographic photometry the dust density in the clouds must be higher than a minimum value depending on the diameter of the clouds and on the size of the structure elements to be recognized. There is also a highest value of the density for these observations depending on the extent of the clouds, on the spatial distribution of A‐type stars, and on the used observing instrument. The calculations were done for an instrument of about 24 inches aperture (Schmidt‐camera of the Jena Observatory). The smallest clouds, which can be investigated with an instrument of this aperture and reasonable demands of the size of structure elements, must have a diameter of 15 pc. The mean dust density of this cloud has to be about 4 · 10 −25 g cm −3 . The density of bigger clouds can vary within a determined interval, e.g. 10 −25 g cm −3 < gD < 10 −24 g cm −3 for D = 50 pc. The considerations were done for clouds with constant density and with a density gradient depending on the distance to the centre of the cloud.