Vieta Lunar Light Ray Reports


Observer: Tony Donnangelo
Date/time of observation: 2004/06/30 01:30 U.T.
Site location: Hummelstown RD 3, PA, USA (40.26° N., 76.75° W.)
Site elevation: 479 feet (146 meters)
Site classification: Suburban
Instrument: Takahashi FS-102 f/8
Magnification: 117x, 158x, 234x
Object: Vieta (Crater)

The sky was generally fair. There were some thin clouds and haze. Seeing was very steady at the beginning of the evening, but deteriorated slightly as the night went on. There was no wind and slight dew.

I started observing at 01:30 U.T. The ray was already in progress, two hours and forty minutes before the predicted time of occurrence. It would likely be visible at an even earlier time. The photograph supplied with the original report showed the ray wider than when I first observed it. Therefore, it may have been advanced and aided in the discrepancy of the times.

The surrounding outer area of Vieta and the western most section of the interior wall were illuminated. The western wall cast a shadow into the terminator. A summit of a raised area within the crater was illuminated, which appeared as a small dot. The ray began just west of this peak. The floor of the crater was totally shadowed except for the ray. There was a thin dark area between the peak and the ray, which was probably caused by the darkened western wall of the raised formation or a shadow cast by the peak. A craterlet was visible within the ray.

The ray was cone shaped, fanning out, and extending to the western wall. It may have been thinner earlier. By 02:15 U.T., the ray broadened significantly, and more of the western wall was illuminated. Within another forty-five minutes, the eastern end of the ray widened further to the south, no longer looking like a pointed cone. There was another craterlet visible to the south of the first one. The western half of the interior wall was illuminated down to the floor, where it met the ever-broadening ray. It was no longer recognizable as such. It was still one hour and ten minutes before its predicted occurrence.