By Daniel Del Valle and Raffaello Lena

 In this age of CCD imagery the visual observer seem to be a throw back to another era. Yet in spite of the many technological advances in amateur astronomy, it is still the human eye connected to that marvelous computer, the human brain that must make the final determination as to what is being seen.

There are moments when the human eye can discern better certain details than a light sensitive computer chip, but there are also moments when perception can be clouded by what an observer expects to see. A balance must be attained if our observing is to be of any value.On the other hand the sheer aesthetic pleasure of observing has much to be said for it.

 These aspects of observing were brought home for me one night, July 26, 2001, as I was contemplating the stark beauty of the waxing lunar landscape. The crater Pitiscus attracted my eye. The compulsion to attempt a representation of what was in the eyepiece was paramount rather than any scientific intent. Pitiscus is located at 50.4E and 30.9S. It is 82 km and a fairly prominent crater.

 I started my drawing at 00:17 UT. The crater's floor was totally in shadow. A craterlet on the rim was in total darkness also. The whole was an interesting interplay of sunlight and shadow. The seeing was good, II on the Antoniadi scale. The transparency was 3.0.  At 00:33 UT my sketch was finished and I was satisfied that I had captured a "lunar moment".
           Just as I was about to put away my drawing materials I took one last look through the eyepiece. My jaw dropped. I blinked a number of times and looked again. There in the darkness of the crater's floor were three bright spots aligned roughly in the shape of a triangle. During the 16 minutes drawing I did not see any bright spots. Immediately I opened my sketchbook and added the bright spots and adjusted the time of my observation.

 Daniel Del Valle observation carried out on July 26, 2001
colongitude 335.8

 My excitement at this unexpected discovery started to wane as I realized that I had seen changing solar illumination on a lunar feature, probably the peaks within Pitiscus catching the sunlight as the terminator slowly moved. A possible TLP never occurred to me at the time.
 After putting my 8- inch Schmidt-Cassegrain and other equipment away I took my trusty Rukl's atlas and looked up Pitiscus. To my surprise there were no prominent peaks in Pitiscus. Its floor had merely a craterlet and a small ridge near it. This was intriguing. Could I have seen and even drawn a real TLP?
 I communicated my observation to Raffaello Lena and the Geologic Lunar Research group with the purpose of confirming or not the possible TLP event. Lena checked the group's archives and Lunar Orbiter photographs. He found that Pitiscus has some low hills near the rim and near Pitiscus A. These could account for the bright spots. Small elevations seen under raking sunlight can appear as bright spots and combined with the shadow be quite impressive.

You can look at Consalitated lunar atlas http://www.lpi.usra.edu/research/cla/menu.html.
 

At colongitude 328.7 Pitascus is visible below (L175 pic. of the Atlas)

 

With higher sun an other spot appears in the center- At colongitude
339.8

At  sunset , colongitude 134.2,  Pitiscus is visible below

http://www.lpi.usra.edu/research/cla/images/
 
Some bright feature on the floor east of Pitiscus A, probably is a  small hill or ridge.
These features are  highly reflective.

 Daniel Del Valle observation carried out on August  24, 2001 at 23:56 UT SCT 20 cms f/10 (225-339 X). Colongitude 341.9.
  A TLP is a event on the lunar surface that an observer could record for just a very limited (short) period of time. There are a number of different explanations to the causes of such an event. A theory is that of an outgassing event . This might indicate the last traces of lunar geological activity. There are also reports of "Lunar impacts" like possible flashes. An other possible theory is connected with the specular reflection of the bright region. Example of a (terrestrial) TLP was seen from the Galileo spacecraft in 1992 (Sunlight reflected on the Pacific Ocean). It might be that some locations on the lunar surface appear brighter than usual just because the light of the sun is reflected in it at that moment. Small elevations seen under raking sunlight can appear as bright spots. This interesting observation is an example.

 This experience shows that the scientific approach with regards to TLP is essential. A network of connected observers with adequate resources can make serious contribution to clarifying TLP reports.