Raffaello Lena,Piergiovanni Salimbeni, Massimo Cicognani, Stefano Basso, A. Bares.
Among the many lunar sites where different visual observers of the past claimed to have recorded a possible LTP, or reflectivity variations, Alphonsus is certainly one of the best known. Tha NSSDC catalog includes all reported phenomena regardless of value of the observation (1-Lunar Transient Phenomena Catalog July 1978 NSSDC W. Cameron July 1978).
Alphonsus crater has been reported as the site of Lunar Transient Phenomena (LTP) in the past.
In NSSDC catalog to the number 705 is reported an event recorded
by Poppendiek, Bond on 1958, November
19 at 04h 00m - 04h 30m UT.
The observers reported a diffuse cloud over central mountain, like a plume.
The Physical Data are reported below
Date & Time (used in calculations): Nov. 19th 1958 at 04:00
Event position: Lat. -13.3° Long. -2.8°
Event illumination: Solar Alt. 1.6° over Alphonsus and Solar Az. 88.7°
Moon status: Phase 0.60 (Waxing) Age 8.3d Colong. 4.6°
Librations (geocentric): Lat. -4.7° Long. 6.5° Total 8.0°
The Geologic Lunar Research group (GLR) set out to coordinate its team
of observers for this possible LTP event.
The lighting conditions of that date were to be duplicated
UT Date Time
Alt° Semi-diam" Long° Lat°
2001/ 8/26 20: 8 19.92 927.43 7.48 -2.09 4.63 1.35
2001/10/24 21: 0 13.78 899.27 3.68 4.38 4.63 1.34
This opportunity would help to verify if any unusual brightening would occur again.
On August 26 a bright spot was recorded by Massimo Cicognani. It appears like a bilobated spot. It appeared to fluctuate sometimes due to the subtle oscillation of the seeing.
This observation was carried out under a seeing very poor using a Cassegrain
41 cm f/17.
Massimo Cicognani photo obtained using a Cassegrain 41 cm F/17 . Observation carried out on 26 august 2001 at 20:05 UT
This bilobated feature was observed again by Lena and Salimbeni
on October 24 at 21:20 and 20:50 UT respectively
Its albedo estimate was 6.5 on the Elger scale. The peak of Alphonsus was 8.5 Elger scale. A bilobated spot very brigth was recorded.
Piergovanni Salimbeni-SCT 20 cm f/10
Raffaello Lena -same date 24 october 2001 at 21:20 UT , Refractor 10
cm f/15 300x.
Our conclusion is that the bright effect recorded in 1958 by Poppendick is not a LTP.
Alphonsus has some ridges and hills near the peak along
the meridian . These could account for the bright spots bilobated detected
by our group.
Images carried out for the GLR project are reported below
Stefano Basso, observation carried out on 30 may 2001 at 20:10 UT SCT
20 cm f/10 at 250x.
Alessandro Bares CCD image - mewlon 250 mm.
Small elevations seen under raking sunlight can appear as bright spots . The whole was an interesting interplay of sunlight and shadow.
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