BAA Lunar Section
Dedicated to amateur research and observation of the Moon
Geological lunar research
By Raffaello Braga
Introduction
The Geological Sub-section of the BAA Lunar Section is involved in the study of the volcanic features of the Moon, notably domes and Dark Halo Craters (DHC). This study is carried out by observing, describing, photographing and measuring these features which, with few exceptions, are not very apparent and thus often overlooked by amateurs. However they are extremely important for the understanding of the geologic history of the Moon and of the extention of the lunar volcanism, and they are also one of the very few fields in which an amateur astronomer can do a useful job, for example by refining the size and height of lunar domes, which are directly related to the characteristics of lunar magmas and their modes of eruption.
To timely plan observations and to promptly exchange them in this field is essential, this is the reason why I have founded a discussion group which will help in organizing the work at the telescope.
http://tech.groups.yahoo.com/group/domilunari/
By joining this group observers can:
Share their observations, drawings, images, etc.
Receive the monthly observing schedule for the domes in the BAA LS observing program (which is also published in the Lunar Section Circulars)
Receive the list of suspected domes to be confirmed
Receive any alerts about urgently needed observations
Discuss any related topic(s)
The group is configured in order to allow members to share small image files (up to 100 Kb, JPEG format). The Yahoo! server works with an updated antivirus that should prevent the diffusion of dangerous files. Moreover the membership is restricted, this should allow me to keep spammers out of the door. It is shared with the participants to the lunar volcanism program of the UAI Lunar Section.
Observations of domes in particular will be collected on the Digital Lunar Dome Archive (also shared with UAI), a bilingual (English/ Italian) Internet web site intended to collect images, drawings and reports. It also includes useful articles and tools for the serious lunar observer.
I invite all BAA lunar observers to participate in geological research, to join the discussion group and to visit the above website. Comments and suggestions to improve it are very much welcomed.
The
Westfall dome classification system
The
classification system itself is designed to describe the physical
characteristics of a doe by means of a combination of letters and
numbers. A brief outline of this system:
Broad
Category:
D
— Dome
DC
— Dome complex (several dome in physical contact e.g., Rumker)
Surroundings:
U
— Uplands
W
— Maria
UW
— Uncertain if uplands or Maria.
Plan,
major axis:
1.
Less than 5 km
2.
5 to 20 km
3.
20 to 35 km
4.
Over 35 km
(always
try to give a more exact size in your written notes)
Border:
a.
Circular (major:minor axes 1.00-1.25)
b.
Elliptical (major:minor axes 1.26-2.00)
c.
Polygonal
d.
Irregular
e.
Too ill-defined to classify.
Profile,
average slope:
5.
Gentle (under 2°)
6.
Moderate ( 2-5°)
Profile,
cross-section:
f.
Hemispherical
g.
Flat summit (platykurtic)
h.
Sharp summit (leptokurtic)
i.
Multiple summit (more then one summit, but of single type)
j.
Hemispherical, asymmetric
k.
Flat summit, asymmetric
l.
Sharp summit, asymmetric
m.
Complex summit (more than one summit and of different types)
Surface
detail, type
7.
Depression (pit, craterlet or saucer)
8.
Elevation (hill, ridge or peak)
9.
Cleft or valley
10.
No observable detail
Surface
detail, position
j.
Central
k.
Off-centre
l.
On margin
m.
Transverse (crosses dome)
n.
More than one such feature
An example of the Westfall system in use would be DW/2b/6f/7j9m8p. Translated, this describes: A dome on a mare, 5 to 20 kilometers in diameter, elliptical in shape with an average slope angle between 2° and 5° and a hemispherical cross section. Its surface contains a central depression, a cleft that cuts across its margin, and several elevations.