Detailed Maps of the Umbral Path

In previous NASA eclipse bulletins, the umbral path was plotted on maps from the Defense Mapping Agency's GNC (Global Navigation and Planning Charts) series which have a scale of 1:5,000,000 (1 centimeter = 50 kilometers). For the current bulletin, we have elected to use maps from the ONC (Operational Navigation Charts) series. The ONC's higher scale of 1:1,000,000 (1 centimeter = 10 kilometers) provides better coverage of major cities, highways, airports, rivers, bodies of water and basic topography required for eclipse expedition planning including site selection, transportation logistics and weather contingency strategies. Charts of the ONC series use the Lambert conformal conic projection.

The path of totality has been plotted on the following ONC charts:

Sections of the above charts where the path crosses land have been selected and divided into 10 maps appearing in the last section of this publication. Northern and southern limits as well as the center line of the path are plotted using data from Table 7. Although no corrections have been made for center of figure or lunar limb profile, they have little or no effect at this scale. Atmospheric refraction has not been included as its effects play a significant role only at very low solar altitudes. In any case, refraction corrections to the path are uncertain since they depend on the atmospheric temperature-pressure profile, which cannot be predicted in advance. If observations from the graze zones are planned, then the zones of grazing eclipse must be plotted on higher scale maps using coordinates in Table 8. See PLOTTING THE PATH ON MAPS for sources and more information. The ONC paths also depict the curve of maximum eclipse at five minute increments in Universal Time from Table 3.

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