Near Ross D (23E, 12N) 1964 May 18 UT 03:54-04:53 Observed by Harris, Cross et al. (Whittler, CA, USA, 19" relector x720, 8" reflector x322, S=G) "White gas obscuration. Moved 20mph, decreased in extent. Phenom. repeated. Drawing." NASA catalog weight=5 (very high). NASA catalog ID 811.
Theophilus 1964 May 18 UTC 01:05-01:15 Observed by Dieke (Baltimore, MD, USA, 6" refractor, x125) "Crescent of crsimson color on SW between rim & flor. Was not present at 0500, nor did it reappear from 0115 to 0245h" NASA catalog weight=3 (average). NASA catalog ID #812.
Linne 1867 Aug 06 UT 21:00? Observed by Buckingham (England?) "Crater in darkness, he saw a "rising oval spot". Other obs. saw it as a triang. Bold black spot pointing to earth, slowly diffused white & drift of white on slope of pyramid. (indep. confirmation?)" NASA catalog weight=5 and catalog ID #155. ALPO/BAA weight=2.
Plato 1964 May 20 UT 01:00-01:30 Observed by Bartlett (Baltimore, MD, USA, 2.4" refractor x117, S=6, T=5). "Orange-red color on W. wall. Vivid" NASA catalof weight=4 (high). NASA catalog ID #813.
C. Brook of Plymouth UK, using a 4" refractor x216, noticed at UT 20:10 dark patches coming and going (in terms of visibility) on the floor of Plato. Occasional views of the central cratelet (seen as a white spot) were glimpsed. The dark patches seen lasted about 1-2 seconds before fading out during each visibility cycle. Teneriff Mountains were checked but no sign of seeing effects that might explain the dark floor patches. By 20:26UT the dark patch effect was fading and by 20:31UT floor detail was visible. Observations ceased at UT 20:34. Seeing conditions were II and the Moon was at a high altitude. Other observers were alerted but came on-line after the effect had finished. ALPO/BAA weight=2.
On 2011 Oct 07 UT 21:45 Gassendi observed by P. Grego (St Dennis, UK,300m Newtonian, x150, seeing III, intermittent cloud) - whilst producing some sketches of the crater - observer noticed a faint point of light inside the shadow filled interior, two thirds of the way out from where the central peaks should have been, towards the SE rim. Some uncertainty in being sure about this spot and after interuption by cloud it was not seen later that evening. ALPO/BAA weight=1 to refelct uncertainty of observer.
M. Cook of Frimley, UK observed a brightening of the crater during this observing session. The cameron 2006 extended catalog ID=346 and weight=3. ALPO/BAA weight=2.