An account in Moselle, France

On February 4, 1979 at around 1:15 in the morning, a witness observed from his vehicle for 30 seconds a luminous object in the sky. This object had the shape of a half-sphere, orange in color, moving from the southwest to the northeast on a horizontal trajectory. The object disappeared gradually, shrinking. This observation case was initially published by GEIPAN in category C, due to lack of information. An internet user, an astronomy enthusiast, spotted this case as possibly being a misidentification with the Moon at moonset; to verify whether this hypothesis was correct, he returned to the observation site in February 2015, 36 years after the facts. Earth and lunar orbits are such that the period when Earth and the Moon find themselves in the same relative positions with respect to the Sun corresponds to 223 lunations, that is, 6,585.32 days: this period is called a Saros; it is used to calculate the interval between lunar or solar eclipses. It is noted that, after this period, which is not a whole number of days, the solar time is therefore not the same. In our case, between the date of the observation and the day of the reconstruction, this period of nearly 18 years had to be counted twice: the exact date falls on February 25, 2015 at 16:36, therefore at a local time notably different from the time of the observation. To choose the best reconstruction date, one must find, near that date, the moments when the azimuth and angular height (elevation) of the Moon are closest to those of the observation. Two dates prove suitable: - February 23, 2015 at 23:55, with a Moon at 1.1° angular height and an azimuth of 288°, a lunation of 5 days and a phase two days before the First Quarter. - February 25, 2015 at 1:00 (therefore the night of February 24 to 25), with a Moon at 1.5° angular height and an azimuth of 292°, a lunation of 6 days and a phase the day before the First Quarter. For comparison, the position of the Moon during the observation at Boulay-sur-Moselle was 1.4° angular height and an azimuth of 286° (the reconstruction was therefore done with a Moon position perfectly similar to 1979), with a lunation of 6.7 days and a phase at the First Quarter. GEIPAN publishes in full the observation report of this amateur astronomer, a very well-documented report, of which here is the conclusion: "The testimony of the time corresponds in many points to the observation made during the reconstruction: the shape is indeed a half-sphere of an orange color tending toward red, its inclination is indeed almost horizontal. The duration of the observation could indeed be short, the Moon being low and located close to the horizon. Moreover, one can suppose the presence of clouds that could hide it at any moment. The observation site shown on the map attached to the gendarmerie report presents a topographical feature that could surprise the witness. Indeed, this site has a slope where one goes from a point at an altitude of 324m to a point at an altitude of 340m over an almost straight distance of barely about 250m. The slope is therefore about 6%. This relief configuration can, for example in the case of driving a motor vehicle, give an illusion of elements located at the horizon bursting forth, which until then were hidden by the rise. These various elements therefore support the hypothesis of a confusion due to the Moon seen under particular conditions (unusual appearance of the Moon at moonset, impression of bursting forth at the top of the rise)." This entirely convincing reconstruction allows this case to be classified as "A": observation of the Moon at its moonset.