PLATO

51.6N BY 9.3W

LUNAR TRANSIENT PHENOMENA HISTORY

DAVID O. DARLING

"At this phase of the Moon the Sun is just rising on one of the best known and most observed lunar formations, the walled plain Plato just on the north 'shore' of the Mare Imbrium. It is about 60 miles in diameter and has a smooth grey floor that seems to darken as the sun climbs higher. This makes it a prominent object, lying as it does in the light-colored upland area between the Mare Imbrium and Mare Frigoris. As H. P. Wilkins remarks, 'Everybody who uses a telescope looks at Plato'. There is a tiny craterlet nearly the center of the floor and two or three others elsewhere that are generally fairly easy to locate under good seeing and lighting conditions. Experienced observers using large telescopes have detected many more and the odd thing is that these craterlets seem to 'come and go' in a curious manner. On occasions when they should be visible they cannot be seen while at other times they are fairly easy objects. The floor of Plato is criss-crossed with delicate whitish streaks which have been carefully mapped but I have never really seen them convincingly, apart from one or two. The south-east part of the crater floor is occupied by a lighter area called the sector. Sunrise on Plato is a spectacle not to be missed. At first, when only the crater rim is catching the Sun's rays, Plato looks like a brilliant oval standing out in the blackness. Then, with startling suddenness, a shaft of light appears on the east part of the floor and quickly extends further west. Shortly afterwards others make their appearance. The floor is now crossed with long pointed spires of shadow and some of the most prominent crater-lets are now visible. Gradually the shadows recede uncovering other delicate details. When most of the floor is lit up, the whitish streaks and numerous white spots begin to appear on the dark floor." The Moon Observer's Handbook by Fred W. Price.

Lunar Orbiter 4 4-127H3 NASA

The graph below shows the number of events reported by age of the Moon, a very small group of events have been reported before sunrise. But on the sunrise period there is a dramatic jump in the number of events reported. This indicates that many of the reported events are sunrise events. Through out the lunation there are a steady number of events reported.

When comparing the phenomena being reported while the crater is in direct sunlight we get whopping 93.2% compared to events reported in the earthshine which is 6.7%. It easy to see that earthshine events are extremely rare. But due to the fact that they have been reported it is strongly recommended to check out this crater when ever you examine the earthshine region.

The crater Plato has an exceptional showing of all classifications of phenomena, making it the second most active formation on the Moon, preceded by the crater Aristarchus, with Proclus and then Schroeter's Valley being the most active after Plato. As you can see the most reported event is brightening followed by gaseous. The gaseous events are associated with the crater floor becoming misty and preventing the small craters on the floor from being seen. The brightening events are reports of star like lights and albedo brightening of the crater rim.

The graph below shows events reported by the month of the year. It is unclear as to why the month of April should dominate the year with all the other months being relatively close in numbers. It may be that during the history of these observations the individuals resided in the northern hemisphere and the extreme harshness of February weather kept observers from viewing. April is the spring month with better observing conditions thus more people were out taking advantage of the pleasant weather.

When examining the L.T.P. events on the libration plot you can see that there squares where the bunching of events takes place and regions on the chart where no activity has happen. When examining this using the 52 bin system. See Quadrant Plots.

The chart below shows the apparent brightness of rim and floor of Plato taken from Santa Barbara 6 image.

The Moon goes through many changes during its lunation. I have been observing the crater Plato for many years and have completed a number of drawings. Making drawings of the lunar feature is an excellent way to better understand and document the changes that take place when the lighting conditions change. Click on Drawings to view the many different aspects of this crater.

You can go to this hyper-link to read an article on History of Changes in Plato.