FIG 1 Clementine Image
A study about the Valentine
dome : observations and classification.
PRELIMINARY ARTICLE
Submitted By: Raffaello Lena, KC Pau and Cristian Fattinnanzi.
Geologic Lunar Research group- GLR
Introduction
In a previous paper [1], we have described Mons Rumker reporting the diameter,
position and slopes of 4 single volcanic forms on its summit.
In this study we describe another complex dome located to the east of Caucasus
Montains and west of crater Linnè B. The dome, known as "Valentine dome", appears
flat with a series of protrusions on its summit.
Interestingly, this dome is reported in ALPO list without specific details
as to the position and diameter of the protrusions and the presence of a rille
(Rima).
As described by Harold Hill in [2], the presence of a rille was reported
and drawn by Alika Herring. His observation was carried out on june 25
1966 using a 61'' reflector [2].
By the way , in the Clementine imagery a rille clearly crosses the dome.
To our knowledge the presence of the rille is difficult to ascertain;
in fact several images we examined don't show the presence of a central rille
as in Clementine image
The "Valentine dome" has been well monitored from
1999 to 2003 during an observational program carried out by the GLR group. The
rille is a difficult feature for visual and CCD observations (though Herring's
drawing matches the Clementine image for the position of the rille) .
Recently the rille was imaged by one of us under a setting sun,
near the moon's last quarter. Since this is period during lunation when comparatively
fewer observers are active,this rille could have generally eluded detection
(though it is noted in Clementine imagery and in Herring's drawing).
In this study we report further
measurements and include our CCD imaging where the rille crossing the
dome was detected.
This has made it possible to extract additional information for the classification
.
Instruments and Measures
Table 1 lists the observers, their instruments,
and the number of the observations they supplied. For each observation,
we calculated the solar altitude (H), azimuth (A), and colongitude, as seen
from the dome, using the Lunar Observer's Tool Kit software by Harry Jamieson.
Furthermore we used CLA, LOPAM and Clementine imagery.
The best images were rotated so that the shadows were oriented orizontally
along the pixel rows. On these images the position and the diameter of the positive
forms was measured in units of pixels.
Furthermore the scale of the images were obtained which allowed diameters
of the concerned features A-D to be expressed in km.
Our results are summarized in Tables II and
III.
Table I Contributing observers and
instruments
contributing
observers
telescope
type Number
of submitted reports
Bares A. Mewlon 250 mm f/10 CCD 2
Cicognani M. Cassegrain 410 mm f/17 Visual and CCD 2
Fattinnanzi C. Newton 250 mm f/6 Web-cam 1
Giuntoli M. SC 200 mm f/10 Visual 1
Lena R.
Refractor100 mm f/15
Visual
3
SC 250 mm f/10
Mengoli G. SC 250 mm f/10 CCD 2
Pau KC
Newton Cassegrain 200 f/11
Web Cam
2
Newton 250 f/6
Table II- Valentine dome
Longitude Latitude
Xi Eta
Diameter (km)
+10.18 ° +30.66 °
+0.152 +0.510
27 x 33
Table III- Prominences located on the surface of the Valentine dome
Prominence Longitude
Latitude Diameter (km)
1
+10.25 ° +31.00 °
5.2x5.6
2
+10.03 ° +30.88 °
5.4x4.8
3
+10.11 ° +30.70 °
4.8x4.6
4
+10.19 ° +30.49 °
5.4x5.2
Observations
Fig. 2 reports the Valentine dome. This image was
obtained by Mengoli on 29 may 2001 at 18:57 UT ( H= 5.34 °, A = 94.06°,
C = 356.47° ) using a SCT 250 mm f/10.
In addition Fig. 3 shows the Lunar Orbiter frame (LOIV-098) taken on May, 17,
1967 at 18:16 UT (colongitude 12.66°).
The image proposed in Figure 4 reveals much finer detail in the dome including
the rille.
This image was obtained by Pau on 16 september 2003 at 21:11 UT using
a Newton 250 mm f/6 ( H= 8.69 °, A = 266.03°, C = 160.43° ) .
FIG 1 Clementine Image
Fig.2
Fig.3
Fig4
Discussion
The coordinates and the diameter of the Valentine dome is reported in Table
II. From our measurement (coordinates 10.18° E and 30.66 º N) we estimated a
diameter of 27 x 33 km. It should be noted that we have found differing coordinates
for the same dome in the ALPO dome list . Furthermore, close inspection
of several our images reveals diameter and , position of 4 single prominences
on its summit (likely cones or tumuli, or peaks).
This dome is a difficul subject and, as reported by Hill in [2]
it has been described by observers variously "as circular, elliptical as well
as heart shaped in outline".
Figure 4 (PAU) reveals the presence of a transversal rille crossing the summit of the dome that "matches" the figure 1.
Using all our available images this dome
may be newly classified, according to the Westfall classification scheme,
as DW/3a/5g/8p 9 n.
The fact that there have been, to our knowledge, only two previous reported observations of this rille in correct position, strongly suggests that this may be a very difficult object requiring specific lighting conditions in order to be clearly defined (appendix 1).
Conclusion
This report demonstrates that lunar domes are difficult features for the
lunar
observer. They require extreme patience and specific conditions of lunar solar
altitude
and good seeing.
Finally the rille was correctly imaged, suggesting it can be detected
also in smaller earth-based telescopes.
This combined effort clearly shows that the
study and classification of these volcanic structures on the moon is far from
being complete.
More observations and observers are needed worldwide in order to observe these
important geologic lunar formations.
appendix 1
dates and times to reproduce
UT Date Time
2003/10/16 9: 5
2003/11/14 21:38
2004/ 1/13 0:55
2004/ 3/12 5:33
2004/ 7/ 8 7:56
2004/ 9/ 5 6: 7
UT Date Time
2004/11/ 3 5:48
2005/ 1/ 1 8:55
2005/ 1/30 23:30
2005/ 3/31 4:20
2005/ 5/29 6: 0
2005/ 7/27 4:22