may be pointed out that the atmosphere was relatively clear (between the clouds) so that the 32' arc solar collimation angle should produce a sharply defined shadow on the ground. Of course, the greater the altitude of the disc above the ground the more diffuse would be the shadow edge due to light scatter/diffusion effects. It should also be emphasized that if the disc was located at the earth's surface one would not expect to find a significant shadow.

This negative was also subjected to digital enhancement. A region measuring 13 X 13 mm centered on the disc was digitized using an aperture of approximately 1 micrometer diameter and 16 bit resolution. A number of color assignments to the density distribution were made to emphasize different features. Unfortunately, the following 4 figures are printed in black and white and do not show all of this rich detail.

Figure 7 is a high reverse contrast image to illustrate two features. First, the density gradient on the left-hand side of the disc which is not visible on the photographic prints (Figures 4 and 6). The same density was found on the left and right sides of the disc. The left side of the disc is not a circular extension of the rest of the disc but is flattened to some unknown extent. Second, the brightness of the lake behind the disc varies regularly from the top of the photograph to the bottom which is consistent with its reflection of collimated sunlight over the range of angles involved.

Fig. 7. A high reverse contrast image (f = 4, t = 1/8 sec.).