Waves in the OH emissive layer: photogrammetry and topography

The waves in the OH emissive layer, which appear on photographs of the sky in the near IR taken with large aperture cameras, are distorted by atmospheric refraction and by a perspective effect. Two methods have been developed to allow restitution of the topography of the waves in a simple way. In the first method a grid is computed, which is superimposed on an enlargement of the original 24 x 36-mm negative frame. In the second method the image is projected on an aspherical surface that is tilted with respect to the enlarger beam. The topography of a wave display, photographed from the Pic du Midi Observatory during the night of 19-20 November 1976, is obtained using both methods. The photometric aspect of the photographs may be interpreted under the simple assumption that the emissive layer has a constant thickness and is ruffled like the wavy surface of the sea.