July 18: Another evening's visual observation from Cambridge with
30-cm refractor, starting before sunset using yellow and
polaroid filters.
Impact site G was very impressive - a large very dark spot, with two components, the Sp. one being a fairly dark 'coma' and the Nf. one being exactly like a satellite shadow. The whole complex transited from 19.51 to 20.19 UT (L2 = 297-314), and the Nf. black spot at 20.13 (L2 = 311). (Chodas prediction was L2 = 314.)
We saw no sign of any fireball from H (in daylight), but from 20.28 onwards, a dark spot emerged from the terminator. It was almost as large as site G but not as dark (intensity between SEB and NEB). It was in transit at about 22.13 UT, L2 = 23 (in bad seeing). (Chodas prediction was L2 = 26.)
There was NO dark spot at presumptive site B (predicted L2 = 360). As impact B was the one that failed to produce a fireball, can we infer that the dark stuff comes from below the clouds, not from the comet? The above transits were by John Rogers but Jonathan Shanklin and James Lancashire also observed all these features and made similar timings.
John Rogers British Astronomical Association. **************************