No. 133: JAN-FEB 2001
At 1832 UTC an azimuth of Jupiter was taken shortly after sunset. The sky in the vicinity of Jupiter was completely clear, no cloud of any type, with but a few small cumulus dotted around the horizon.
About five minutes later, having completed the calculations, the observer again looked out to see a ribbon type cloud, broken in formation, stretching almost from [the] eastern horizon to [the] western horizon. If the estimated height (see below) is reasonably correct, then the bandwidth couldn't have been more than a few hundred feet, apparently more cigar-shaped in cross section than flat, the maximum axis being horizontal, the minimum vertical. The cloud was fairly consistent in density, and at a fairly stable altitude, not undulating or rippled, having the consistency of a small cumulus cloud (white and fleecy), but also translucent.
Initially, it was thought to be a condensation trail, but this was shortly dismissed as it was considered too low (estimated to be less than 10,000 ft altitude, probably around 7,0008,000 ft). Both ends of the cloud were checked with binoculars but no aircraft was evident; however, as a yardstick, and by good fortune, one did appear around 1910, presumed to be at the usual 30,000 or so feet, heading west-south-westward.
(Bennett, Paul; "Ribbons in the Sky," Marine Observer, 70:177, 2000.)
Comment. If not a condensation trail, the next best guess would be a meteor trail, although the altitude is also very low for one. A bolide streaking across the sky at such a low altitude at night would have created a spectacular luminous display and probably considerable sound as well.
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