Lunar Transient Phenomena


The definition of Lunar Transient Phenomena (LTP) is a short term phenomena observed with respect to the lunar surface. Typically they have been seen as coloured glows, flashes, brightness variations, obscuration of underlying detail, and shadow effects.  There have been nearly 3000 reports of LTP, going as far back as AD 557. We now know however that many of these can probably be explained by: atmospheric / telescope optics effects, or observer misinterpretation. The general lunar science consensus is that the Moon is geologically dead, and apart from meteorite impacts seen in Earthshine, no other effects should be bright, or large enough, to be seen in a telescope from Earth. Nevertheless astronomers continue to report LTP, and it is the job of this observing programme to study these observations to see what scientific explanations can be offered or put to the test.




Given that LTP are still being observed, although many cast doubt upon their existence, the present day goals of the observing programme are as follows:


1)      Repeat Illumination/Libration Observations to Disprove Past LTP: To observe features, under the same illumination (and where possible libration too) to when LTPs were seen in the past in order to get an understanding of the “normal appearance” of these features. Sketches or even visual descriptions may be enough to show that the original observer was mistaken in their interpretation. However capturing images (or computer visualisations e.g. LTVT software), allows us to model the effects of atmospheric (seeing blur or scatter), spectral dispersion, or optical chromatic aberration, and find out if these can offer more down to Earth explanations of the LTPs

2)      Observational Archival: To archive all observations received, the vast majority being non-LTP, and to supply this material to other groups within the Lunar Section, for their use.

3)      Educate: To inform observers about the common mistakes that have been made in the past over LTP observing, and to offer some standard tests to perform at the telescope should anyone suspect that they have actually found a LTP.

4)      Systematic LTP Searches: TLP, if they exist, must be exceedingly rare e.g. one event per hundreds to thousands of hours of observing. Modern imaging cameras and automated change detection software are essential for such searches, and success is not guaranteed.

5)      Catalog and Analysis: The ultimate goal is to catalog, weight (according to reliability), and analyze all LTP reports for publication and use by lunar scientists or astronomical historians.



What do you do if you see a LTP?:

There are seven categories described below. Click on the most appropriate one to what you have seen and follow the instructions.

1)      Colors

2)      Brightness changes (day side)

3)      Brightness changes (night side)

4)      Flashes

5)      Movement

6)      Obscurations

7)      Shadow related



On-Line Resources:

1)      The Lunar Observer (TLO) newsletter with an LTP section

2)      Repeat illumination predictions for the coming month

3)      A Twitter LTP alert system

4)      Research work on LTP by Prof Arlin Crotts of the University of Columbia, NY, USA

5)      Lunar Impact Flash observing

6)      The 1963 Aristarchus Events

7)      The NASA catalog of LTP (1978)

8)      The 2006 extension to the LTP catalog

9)      Analyses of Lunar Transient Phenomena (LTP) Observations from 557–1994 A.D. by W.S. Cameron

10)   A Wikipedia entry on LTP



For further information contact the ALPO LTP coordinator: Dr Tony Cook on atc @