Mission Statement

The Study of the Lunar Surface

The Moon is the Earth’s only known natural satellite and occupies an elliptical orbit at a mean distance of 384,400 km (238,855 miles) from its parent planet. With a diameter of 3,476 km (2,160 miles) it is larger than the planet Pluto and over 70% the diameter of the planet Mercury.

Because the Moon revolves on its axis exactly once during each orbit about the Earth, the same side of this large satellite always faces the Earth. The inclination of the Moon’s orbit and other factors allow us to see approximately 59% of its total surface. It is this surface, larger than that of the United States and Australia combined, that is the object of study by the A.L.P.O. Lunar Topographical Studies Section.

To the naked eye the appearance of the Moon exactly repeats itself every month as the terminator (the dividing line between lit and unlit regions) marches across the surface of the Moon. Because of the orbital mechanics involved, however, a telescopic view reveals that changes in the lighting, and the resultant shadows, are not exactly duplicated each month. This slight change in lighting can provide a surprisingly different view of the same feature each month for many years. This, combined with the almost infinite detail available to even modest backyard telescopes, can make the topographical study of the Moon a lifelong adventure.

It is the mission of the Lunar Topographical Studies Section to observe, study, and record the many surface features of the Moon. These features include such broad categories as mountain chains and isolated peaks, impact rays and bright spots, lava flows and wrinkle ridges, domes, rills, and scarps, and craters of every conceivable size. The instrumentation used by Section participants varies from modest 60mm refractors to massive Dobsonian mounted reflectors. Lunar observers utilize imaging equipment that ranges from traditional film cameras to the latest in digital and video systems. Filar micrometers, photoelectric photometers, and a host of other specialized tools are brought into play in the pursuit of topographic studies but such sophistication, useful as it is, is not a prerequisite. Many insightful and valuable observations are still being performed by those with telescopes of modest size who sketch what they see.

Because of the broad nature of topographical observations, this Section also stands ready to assist other A.L.P.O. Lunar Sections in the pursuit of their research programs. Requests for corroborating observations from the Lunar Transient Phenomena Section and Selected Areas Program are always quickly researched through the Section’s computerized archives and assistance provided whenever possible.

In order to be of scientific value, all observations submitted to the Section Coordinator should include the following:

  • Name and location of the observer
  • Name of feature
  • Date and time (UT) of the observation
  • Size and type of telescope used
  • Seeing: 1 to 10 (1-Worst 10-Best)
  • Transparency: 1 to 6
  • Magnification (for sketches)
  • Medium employed (for photographs and electronic images)
  • Any other vital technical data as it relates to the observation made
   Lunar Selected Areas Project

Introduction

The percentage of sunlight reflected by the surface of the Moon varies as the phase angle changes throughout the lunar month. Taken a step further, observers are well aware that one area of the Moon reflects more light (e.g., a crater rim or central peak) than another region (e.g., the maria), regardless of the phase angle. These areas, in turn, also vary in appearance as the illumination changes. These differences in tone are generally more conspicuous at Full Moon, and the investigation of light and dark areas of the Moon is an interesting observational endeavor.

While there is a definite requirement to know how various lunar features change their normal appearance throughout a lunation in response to variations in phase angle, even more intriguing are those lunar features that behave in an unusual, sometimes unpredictable, and non-repeating manner as solar illumination changes. The A.L.P.O. Lunar Selected Areas Program (SAP) is chiefly concerned with systematically monitoring regular and cyclical long-term variations during many lunations of specifically designated, or “selected”, areas on the Moon. In general, the SAP is designed to intensively study and document for each of these features the normal albedo changes in response to conditions of varying solar illumination.

For additional information see: Program Overview

Selected Areas Program Observing Documents:

   Suggested Areas of Study

Members of the Lunar Topographical Studies Section observe, study, and record the many surface features of the Earth’s Moon. Some observers make their observations based upon the lunar features which are well placed at the time, others prefer to work on observing projects having a more formal structure. In order to enhance the observing experience of all lunar enthusiasts, we have listed here several areas of study which can be undertaken.

All observers should be aware that several formal programs related to topographic features are currently active within the A.L.P.O., they are:

  • LUNAR TRANSIENT PHENOMENA – The study of short-lived events on the Moon such as lights, glows, mists, and obscurations.
  • SELECTED AREAS PROGRAM – The study of albedo changes in selected features.
  • BRIGHT AND BANDED CRATERS – The study of craters identified by their bright appearance and/or having bands of light and dark on their interior walls.
  • DARK HALOED CRATERS – The study of craters surrounded by dark ejecta.
  • LUNAR DOME SURVEY – Observations of low-profile swellings on the lunar surface to catalog their positions and properties.
  • BRIGHT LUNAR RAYS PROJECT – The study of the bright splash patterns formed by impacts on the Moon.
  • GENERAL TOPOGRAPHICAL STUDIES – Any observations of the lunar surface which do not fit into any of the above categories.

Submitting an observation to one of these programs does not preclude the submission of duplicate observations to other programs for inclusion in their studies.

Lunar observers seeking areas of topographical study for their own satisfaction might consider some of the following, keeping in mind that sufficient interest and submissions to the Section Coordinator could lead to the adoption of the program as a formal project.

  • VERTICAL STUDIES (1) – Using imaging equipment or micrometers to determine the heights of lunar mountains and the depths of craters is well within the capabilities of backyard astronomers especially when utilizing the software in Harry Jamieson’s Lunar Observer’s Toolkit.
  • VERTICAL STUDIES (2) – Those not suitably equipped to directly measure lunar heights and depths can utilize images produced by orbiting spacecraft, particularly for those features too small for typical amateur equipment.
  • INNER SLOPES – Using the shadow method to determine the inner slope angles of small (10-15 km) craters.
  • VOLCANIC CONES – High resolution electronic images now make it possible to detect and catalog lunar volcanic cones.
  • RILLES – Another area for potential discovery of uncataloged features for those capable of truly high-resolution imaging.
  • FARSIDE STUDIES – All of the above studies (and more) can be conducted on the farside of the Moon using appropriate spacecraft images. There is no logical reason why the analysis of such data should be strictly the province of the professional community.
  • PHOTOMETRIC STUDIES – Those having photoelectric photometers or suitable CCD imaging equipment could perform valuable studies related to the brightness differences and/or changes of various lunar features.
  • COLORIMETRIC STUDIES – Similar to photometric studies, work also can be done on the color differences of the lunar terrain.

These are only a few of the specialized areas open to observers of the lunar surface. Your observations in these or any aspect of lunar topography are always welcome.