Anthony Cook
Institute of Mathematical and Physical Sciences
University of Wales Aberystwyth, Penglais,
Aberystwyth, Ceredigion, SY23 3BZ, WALES, 
Email: atc "at"

A Transient Lunar Phenomenon (TLP) is a short-lived unexplained change in the normal appearance of a localized area of the Moon, and can include coloured and colourless glows, grey shadows, brightness changes and obscuration of detail on the lunar surface. One long standing debate in lunar science concerns whether these phenomena are real physical events in the vicinity of the lunar surface, or just observing artifacts or misinterpretations. During a couple of nights in late 1963, experienced observers at Lowell Observatory Flagstaff, Arizona made two of the most famous observations of TLP known as The 1963 Aristarchus Events. After five decades we re-examine the background and reliability of these observations and discuss possible terrestrial and lunar explanations for what was seen.
Revisiting The 1963 Aristarchus Events

Robert O'Connell and Anthony Cook

Journal of the British Astronomical Association123(4), pp. 197-208, (August 2013)

Robert O'Connell
Gainesville, Florida

Full paper PDF download
Click Here

(Permission granted
 JBAA July 29, 2013)

Please visit the BAA web site
James Clarke Greenacre charting the lunar surface in the early 1960s for Project Apollo at the 24-inch Clark refractor, Lowell Observatory, Flagstaff Arizona. Greenacre was the lead observer and official USAF spokesman for The 1963 Aristarchus  Events. (Image courtesy Greenacre Family).

Below are nine PDF files containing ​3,469 scanned pages
 of mostly lunar material from the
Journal of the Association of Lunar and Planetary Observers
"The Strolling Astronomer"
(1947 through 2000)

PDF file contents description

JALPO Vols. 01-05 (33 mb)

JALPO Vols. 06-​ 09 (32 mb)

JALPO Vols. 10-14 (26 mb)

JALPO Vols. 15-17 (27 mb)

JALPO Vols. 18-20 (30 mb)

JALPO Vols. 21-23 (29 mb)

JALPO Vols. 24-27 (29 mb)

JALPO Vols. 28-33 (28 mb)

JALPO Vols. 34-42 (38 mb)

Figure 6. Airbrushed chart identifying the locations, sizes, shapes, orientations and colours of the R1, R2, R3 TLP on 1963 October 30, IAU directions, North top right. This rendition was produced by ACIC scientific illustrator Patricia M. Bridges. Bridges noted she rendered the TLP with a great deal of input from Jim Greenacre and Ed Barr. (personal communication 2010). The solar illumination in this depiction is somewhat lower than that experienced by the observers on this night. NOTE: Baseline seeing was very poor (2) improving to better moments of 3-to-4 on USAF lunar seeing scale of 0-10. Event duration: 25 minutes. Lunar altitude range: 29 to 33 degrees. Magnification ~500X or ~21X per inch of aperture with zoom eyepiece providing ~430 to 1050X. According to USAF Lowell site director, William D. Cannell, "0 to 4 comprise the seeing range for the majority of the time" for the Apollo lunar mapping work done with the 24-inch Clark refractor. He also noted "We normally use a magnifying power of 500 ...". (1962 reference link). Also see Chuck Wood's August 25, 2013 LPOD discussion of this night's observation.
Figure 10. This Bridges rendition depicts R4, R4a and R5 TLP on Nov 28 in the same manner as was carried out for Figure 6 for the Oct 30 observation. The illumination here is higher than that seen by the observers during the reddish TLP episode on this night. NOTE: The four observers involved this night were Jim Greenacre, Fred Dungan, Ed Barr and Lowell Observatory Director John Hall. Event duration: 75 minutes. ​Seeing: became mostly "excellent". Lunar altitude: 25 to 39 degrees. Magnification: unknown. See Oct. 29, 2013 LPOD for our discussion of some observational anomalies on this night.
Below are Figures 6 and 10  from the paper with partial captions depicting the reddish TLP seen in  Oct. and Nov. 1963 at Lowell Observatory through the 24-inch Clark refractor. Additional notes have been added in white text.
Web site © 2021 R. O'Connell and A. Cook. All rights reserved.
 Last website update: 
October 22, 2017

- Paper references of particular note - 

'Langrenus: Transient Illuminations on the Moon' 
                                     Dollfus, A. 2000 Icarus 146 2 (abstract)

                                                 Full text PDF Icarus paper


Related articles/postings:
                    'A TLP in Langrenus Crater', J. Br. Astron. Assoc., 109, 6, 1999
                    Chuck Wood's LPOD "No Title", November 32, 2013 (sic)
Night 2 - November 28, 1963 UT
Night 1 - October 30, 1963 UT

Repeat Illumination Observations for 'The 1963 Aristarchus Events' 

Night 1 Repeat Illumination Observations    (revised Dec. 4, 2013)

Night 2 Repeat Illumination Observations    (posted Dec. 3, 2013)