Observer: Tony Donnangelo Date/time of observation: 2004/05/01 03:01 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: 250x Object: Clausius
It was very cloudy early in the evening. The weather map indicated a possible hole in the clouds occurring later and lasting approximately an hour. It would be necessary for the ray to start earlier than the predicted time of 04:37 U.T. to view it before the clouds moved back in. Dave Mitsky’s initial report stated the ray was cone shaped when first observed. There might be a chance to see it earlier and thinner.
I got lucky. At 03:01 U.T., the clouds parted. There was a slight breeze, still some haze from high thin clouds, seeing was poor, but I could observe. The ray was already in progress. It was 1 hour and 36 minutes before the prediction and possibly could be seen even earlier.
A very thin, long shaft of light emanated from a ridge west of Clausius at the red arrow. It extended to the craterlet indicated by the orange arrow. There appeared to be another very thin, short ray near the yellow arrow. Because of its appearance later on, I believe that sighting was actually the smaller of two ridges, west of the yellow arrow and running southeast to northwest, being illuminated. Poor seeing and the opportunity to observe it with the sun higher makes me uncertain.
Clausius’ rim and surrounding area was illuminated with its floor totally shadowed. The terminator was just west of the ridge’s crest where the ray originated. The eastern wall of this ridge and the ridge formation north and west of the craterlet were illuminated. The flat area between these two structures was shadowed, except for the ray.
Within five minutes, the ray began to widen. The rim and western interior wall of the craterlet was now illuminated. By 03:12 U.T., the ray was more cone-shaped and extended past the craterlet. Within ten minutes, it was considerably wider and continued to do so quickly. At 03:35 U.T., it became very cloudy. The ray was broader, and another very thin ray appeared just to the south of it. The craterlet was fully illuminated. Within five minutes, the sun rose considerably on the western part of the floor area. The pointed shadow of a peak was visible on the surface between the two widening rays. Seeing conditions now made it necessary to end my observing session.