Diagram (not drawn to scale) showing plotted compass directions to the last visible point on a fireball path. (The point denoted by L in [next diagram].) Black dots represent positions of various observers. Each arrowed line is directed toward the last visible point as it was estimated by the individual observer. The oval area, which includes points of intersection of all observed lines of sight taken in pairs, marks out region in which meteorites have probably fallen.
If, in addition to compass directions to the observed endpoint, scientists can also obtain the apparent elevation, in degrees, of this point as seen by the various eyewitnesses, then with the help of a little trigonometry, they can fix the position in space of the end-point itself rather than the position of its projection on the surface of the earth.
This same procedure can be followed in fixing the space-position of any well-observed point on the fireball path. It therefore becomes possible when both elevations and compass directions are reported for several points on the fireball path to determine the flight-path or, as it is technically called, the trajectory, of the falling meteorite through the atmosphere. Trajectory determinations are of great scientific value.
You can estimate the compass directions and elevations to the important points on a meteorite trajectory at the actual time of fall. Or you can have the scientific field party make or check your measurement at some later time by setting up a surveying instrument at the very point from which you saw the fireball.
The accuracy of your measurements can be improved if you have been able to “line up” the point, L, at which you saw the fireball disappear, with some familiar object on the horizon, such as a church steeple, a tall tree, a telephone pole, or a lightning rod on a farm building. You will recall that an eleven-year old girl provided one of the field parties from the Institute of Meteoritics with an excellent observation of the point of disappearance of the Norton fireball. She was able to do this because she remembered just where it went out of sight behind a familiar landmark.
Method for locating a point on a fireball path. (In this case the point of disappearance, L.)
O₁ First observer. A₁ Apparent height of point of disappearance (50°). C₁ Compass direction of point of disappearance (N 62° W). O₂ Second observer. A₂ Apparent height of point of disappearance (45°). C₂ Compass direction of point of disappearance (N 42° E).
If the fall occurs at night, you can help investigators greatly if you are familiar enough with the brighter stars to use them as “skymarks.” You simply note as quickly and sharply as you can just where the fireball path was in reference to those prominent stars. This alert observation of yours will at least be a great aid to investigators who are searching for meteorites that may have fallen from the fireball; and, moreover, there is no telling what else your quick eye might have captured for science.