Transient Lunar Phenomena TLP

Since the 1950s, various controversial glows and obscurations have been reported on the lunar surface by amateur astronomers. In general, these "events" have been associated with specific craters such as Alphonsus, Plato, Aristarchus, and Gassendi, although much more obscure craters, like the diminutive Torricelli B, have also generated alerts. Undoubtedly TLP "hunting" is on the very fringe of amateur astronomy, on the borderline between science and pseudoscience and, as such, it attracts a fair number of cranks. There is no shortage of weirdos out there who are convinced that alien abductions really occur or that astrology means something. There is also no shortage of cranks who want to be regarded as the next Einstein or Stephen Hawking, but without putting in the mental effort to indulge in mainstream science. For 11 years (1980-1991) I was an active member of the BAA Lunar Section TLP network: a network of lunar observers dedicated to responding quickly to claims of glows and obscurations on the Moon. I had a rather unique role in that team. I was determined to photograph, and later videotape, craters during TLP alerts, in order to try to prove or disprove what was happening. What did I gain from that experience? Well, the main thing I learned was that not only does the Moon look different every night due to librations, lunar distance, and the position of the terminator, it looks very different due to the effects of atmospheric spurious color. If you look at the crater Plato when the Moon is high in the sky, at lunar perigee (closest to Earth) and with a libration moving it nearer to the center of the disc it looks perfectly normal. However, if you look at it when low down, close to apogee and when librations make the crater look highly elliptical it looks blurred and fringed with color. It is under those latter circumstances that TLP alerts were normally generated. The imaging situation in the 21st century is far removed from the situation in the early 1980s when I was a keen lunar observer. In those days the human eye could easily see more detail than a photograph could capture. Now the situation is reversed. A stacked composite of hundreds of webcam frames can capture all the details that even the keenest observer can see, and more . . . and guess what . . .? Mysteriously, there are virtually no TLP being reported! I think this reveals TLP for what they really are: effects of the Earth's atmosphere.

However, the BAA Lunar Section is now analyzing all those old TLP reports and alerting interested parties to repeat illuminations of features that generated TLP

alerts in the distant past, to try to see whether the illumination angle of the feature is the critical aspect. A list of these features is generated by Dr. Tony Cook and is available at www.lpl.arizona.edu/~rhill/alpo/lunarstuff/ltp.html.

Some of the historic TLP were reported by some quite famous names in astronomy so it would be nice to think that there was some substance to them, even if I remain rather sceptical, despite being a past member of the BAA TLP team! The red glow in the crater Gassendi, on April 30, 1966, was a particularly well-documented mystery and a handful of other cases make me wonder whether I should be such a cynic!

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