Investigations into the Apparent Shape of the Sky

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Summary

It is shown that the quantitative estimates of the apparent shape of the sky cannot be explained by the geometric and physical conditions of the atmosphere. Observations of the angular elevation of the midpoint of the arc: Horizon-Zenith, show that with increase in cloudiness the sky appears to become flatter. The effect of different cloudtypes on the apparent shape of the sky is explained by the structure of the clouds themselves. However, no significant relation between the ceiling height and sky shape was found.

Aside from the influence of the angular elevation of the terrestrial horizon, an important factor determining our impression of the shape of the sky is the distance between observer and topographic horizon as well as the contour of the foreground, as is shown by special measurements. This conclusion is confirmed by the relation between visual range and the apparent shape of sky as well as measurements through red color filter.

* Pan American-Grace Airways, Inc., Santa Cruz, Bolivia.

** Geophysical Laboratory, The Pennsylvania State College.

Summary

It is shown that the quantitative estimates of the apparent shape of the sky cannot be explained by the geometric and physical conditions of the atmosphere. Observations of the angular elevation of the midpoint of the arc: Horizon-Zenith, show that with increase in cloudiness the sky appears to become flatter. The effect of different cloudtypes on the apparent shape of the sky is explained by the structure of the clouds themselves. However, no significant relation between the ceiling height and sky shape was found.

Aside from the influence of the angular elevation of the terrestrial horizon, an important factor determining our impression of the shape of the sky is the distance between observer and topographic horizon as well as the contour of the foreground, as is shown by special measurements. This conclusion is confirmed by the relation between visual range and the apparent shape of sky as well as measurements through red color filter.

* Pan American-Grace Airways, Inc., Santa Cruz, Bolivia.

** Geophysical Laboratory, The Pennsylvania State College.

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