PROCLUS

16.1 N by 46.8 E

LUNAR TRANSIENT PHENOMENA HISTORY

DAVID O. DARLING

"A brilliant crater west of Mare Crisium, 18 miles in diameter and 8000 feet deep. Proclus is one of the brightest points on the Moon, and is the centre of a ray-system; there is a low central mountain. The rays cross Mare Crisium, but not the Palus Somnii, which is bounded by rays to either side. There are both bright and dusky bands on the inner walls of Proclus." New Guide to the Moon 1976. By Patrick Moore.

Clementine image, NASA

The crater Proclus has a very interesting history when looking at the historic L.T.P. record. When looking at the most active days during the lunation three days stand out. They are eight, ten and fifteen day old Moon. My own experience with this crater is observing a strange electric arc blue color during a lunar eclipse and an extreme darkening event inside the crater. Also changes in albedo have been documented during extended monitoring of this crater. It was also mentioned in one of my many books on the Moon that in the early days of Selenology, observers reported that Proclus was a dark feature, not what it is today being one of the brightest on the Moon. The brightness of this crater can rival that of Aristarchus.

Graph © by David O. Darling, Director L.T.P. Research.

The graph below shows the apparent floor brightness using the Santa Barbara CCD software by doing a cross section of the lunar formation going from the outside wall through the center of the crater then going to the outside wall again. Extensive observations of this crater documenting the albedo off the cardinal points of the crater can produce some very interesting results. The crater Proclus has also had a history of fluctuating in albedo intensity in just a few hours time while other bright features remain constant.

Graph © by David O. Darling, Director of L.T.P. Research.

I personally have witnessed a number of L.T.P. events. The first took place during a total eclipse of the Moon when the crater appeared electric arc blue while inside the umbra shadow. I have seen this kind of response only once in all the eclipses I have documented. The second event was an extreme darkening inside the crater taking on the appearance of a shadow. This was incredible since the crater was in full sunlight with no shadows being cast. I have also observed twice the albedo fluctuation of the crater in just a few hours while other features remain constant. You can also learn more about the appearance of this crater by examining so of my drawings of Proclus.

I have also done extension evaluation of the possibility that lunar librations was a factor in the lunar transient phenomena. When taking the Earth's Selenographic Longitude and Latitude and plot it on a combined libration scale I found that a greater occurrence took place when the Moon librated toward the southwest. To give the reader a better understanding of what this means the Earth's Selenographic Longitude and Latitude is the position on the Moon that the observer would have to stand in order for the Earth to appear at zenith in the lunar sky. This process changes all the time, and no two months may be the same. I have completed a plot on Combined Libration Scale chart shown below. Each black spot represents a specific L.T.P. event. This highly useful tool was developed by the British Astronomical Association (B.A.A.) lunar section. To examine the L.T.P. events by 56 bin within the four quadrant. Click here to view.

If you graph the data presented in the libration chart and break it down to the four sections you find the south west quadrant is the most active. This would seem to indicate that libration is a factor. This may be caused by the brightness of the crater rim. The northwest rim is noted for its high albedo.

Continuing to examine this phenomena I want to conclude by showing which type of phenomena is the most reported. The two most common are brightening and darkening events, which is the two types of events I have also witnessed.

Conclusion: This crater has an extraordinary history of events. It is a crater in conflict with itself in that it has had some exceptional brightening events reported and some very dark events reported. This only deepens the mystery of what is going on with this crater. I certain that if you continue to monitor this crater you will not be disappointed when it comes to L.T.P. events