Plato a study about albedo variation
by Raffaello Lena ( GLR group)
Data collected by R. Lena, C. Fattinnanzi, KC Pau, Pg Salimbeni, M. Cicognani, G. Mengoli, L. Comolli and A. Zanazzo
Introduction
The NSSDC catalog includes all reported phenomena regardless of the perceived weight of the observation.
During a GLR project we studied a preceding observation by Kelsey, 1967 April 18.
The event is described: " Streak on Plato's floor showed slight enhancement in red filter
compared to blue filter. Later, a 2nd streak formed. Probably the sun shining thru a valley in the rim. Red enhancement permananet? (Wise suspected a blink here 6h eaelier). Weight=3"
The observations carried out on May 9 2003 match the lighting condition to within +- 0.1 for the
Plato event by Kelsey.
The local altitude of the Sun H, azimuth of the Sun , A, and its colongitude C, were calculated with the Lunar Observer's tool kit software by H. D. Jamieson.
For may 9 2003 at 19:00 UTC
Solar Altitude over Plato = 1.101°
Solar Azimuth = 91.933°
Co-longitude = 11.499°
An event described by Kelsey
Lena reported :"At 20:15 UTC i saw 2 streaks on the Plato's floor. The floor was in shadow.
Over the next 30 minutes i saw the shadow's retration, showing how rapidly the appearance of this area changes with increasing solar elevation.
The reported streaks by the Kelsey, 1967 April 18, were very well visible.
The streaks showed an "apparent blink" using blue filter (W 80A) and red filter (W 25A).
In fact the 2 streaks on Plato's floor showed slight enhancement in red filter compared to blue filter. Blink was conducted every 5 minutes
The observation by Lena was carried out using a refractor 100 mm f/15 at 150-170 x , under a seeing of II-III Antoniadi .
Using the Elger scale their albedo values was estimated as follows:
Blue light= 2.0 +- 0.5
Red light= 3.0 +-0.5
So the streaks show a red component.
This GLR observation that match the Kelsey's event, on different date but at the same colongitude, suggest strongly that this phenomenon is a normal effect
Albedo Variation
We have studied , and documented , the albedo changes in response to conditions of varying solar illumination. Furthermore the following notes and drawings are a representative selection of these features and give a basis for further observations.These data may be used in order to study future TLP events.
KC Pau 13 november 2002 11:10 UT - 13:46 UT, Takahashi CN212 colongit. 12.77° - 14.09° - H 2.56° - 3.37°.
C. Fattinnanzi , 20 may 2002 at 19:31 UT, Newton 200 mm C= 16.46° H= 4.03°.
R. Lena , 12 may 2000 at 18:30 UT, Refractor 100 mm, C= 18.60° H= 4.90°.
R. Lena , 15 september 2002 at 20:10 UT, Refractor 100 mm, C= 18.80° H= 6.60°.
M. Cicognani , 2 february 2001 at 19:00 UT, Cassegrain 41 cm C= 22.52° H= 7.60°.
C. Fattinnanzi , 22 april 2002 at 20:10 UT, Newton 200 mm webcam Vesta Pro, C= 34.95° H=14.67°.
M. Cicognani , 23 april 2002 at 21:00 UT, Cassegrain 41 cm C= 47.55° H=21.68°.
M. Cicognani , 5 february 2001 at 22:00 UT, Cassegrain 41 cm C= 60.46° H=28.32°.
M. Cicognani , 20 octobre 2002 at 20:00 UT, Refra ctor 120 mm, C=84.89° H= 38.10°.
M. Cicognani, (sunset) 8 august 2001 at 03:00 UT, Cassegrain 41 cm C= 135.81°
H= 30.91°.
M. Cicognani, (sunset) 9 august 2001 at 03:00 UT, Cassegrain 41 cm C= 148.01°
H= 25.12°.
M. Cicognani, (sunset) 10 august 2001 at 03:00 UT, Cassegrain 41 cm C= 160.22°
H= 18.46°.
A. Zanazzo e L. Comolli, (sunset) 30 august 2002 at 05:00 TU , Trischiefspiegler 30 cm and webcam Vesta pro, C= 175.11° H= 9.98°.
G. Mengoli, (sunset) 31 august 2002 at 02:50 TU , Takahashi Mewlon 20 cm HX516 Starlight-Xpress. C= 186.21° H=3.12°.