In some recent columns, I've listed a few dates when the moon will appear near some bright evening sky planets. The idea was that being close to the moon would make it easier to locate a planet near the moon. We could then point our telescope at this planet and examine it in detail.
But if you do not aim your riflescope at Saturn, the moon is the most breathtaking target you can bring into the field of view of your telescope.
Most any small telescope will show the dramatic landscape of the moon with craters, mountains and smooth lava lines. Even good binoculars will show some of the larger features of the moon.
The Moon is just small enough and just far enough away to make its smaller surface features invisible to the naked eye. Take a small magnification into the equation with a small scope and you will see remarkable lunar details.
The reason is twofold. First, the moon is about 2000 miles wide and relatively close to 240,000 miles. Apollo astronauts traveled the Earth-Moon range in three days. The second reason for the clarity of a telescopic moon view is that there is no atmosphere around the moon that could darken and hide lunar surface details.
Changed moon faces
If you look at the moon through your telescope, it can greatly affect that, you'll see.
Surprisingly, the full moon, while in many ways a favorite phase, is currently the worst time to observe the moon through a telescope. The full moon has few, if any, shadows.
It is a deep sun casting shadows over the face of the moon that really brings out details. During a full moon, sunlight hits the entire earth side of the moon. Moonbeams, these bright stripes that emanate from some lunar craters, can be more visible during a full moon. The full moon in September falls on the 24th of September and is called Harvest Moon
A thin crescent moon just after a new moon is an irresistible telescope target. The fingernail thin arc of a moon two days after new often reveals a dimly lit "dark" side of the moon. It is a phenomenon called "earthshine" and is caused by reflected sunlight from the earth. It is also known as "DaVinci Lighting" because Leonardo da Vinci was the first to explain the effect. Search for the moon at this stage on the evenings of September 1
For most amateur astronomers, the preferred phase of the telescopic viewing of the Moon is about one week after the new moon around the first quarter phase. In the first quarter, the moon shows us a half-lit face. Of particular interest during the first quarter phase is the lunar terminator, the dividing line between the shaded and sunlit portions of the moon. For places along the lunar terminator, the sun is just rising. This low sun casts long shadows and this makes moon details in bold relief. On the evening of September 16, look for the imminent first quarter of the Moon.
A certain spot on the moon makes about two weeks of darkness, followed by two weeks of sunlight, which is the result of the months-long orbit of the moon around the earth. The moon is "locked" in its orbit around the earth and this keeps the same side of the moon always pointed at the earth. We did not get a glimpse of the other side of the moon until the Soviet unmanned spacecraft Luna 3 photographed the back of the moon and returned a blurred image showing only major features in 1959.
When I was in elementary school, we were taught that the moon is a dry, waterless world, but the exploration of unmanned spacecraft in recent years has revealed ice in the crater floors at the poles of the moon. In these dark, ever-shaded areas where the sun never shines, water in the form of ice is present in surprisingly large quantities.
If you look at the moon through your telescope, you may wonder (or be asked): "Can I see the flag?"
Not by any means, not by a terrestrial telescope. All Apollo airfields with some of the US flags planted by Apollo astronauts have been mapped in the years since the landings of unmanned moonborne missiles. They reveal the lunar module bases as well as human and lunar rover tracks in the lunar soil around the landing sites.
As for backyard observers with the best modern amateur telescopes, features as small as about 1/2-mile across the smallest features we can expect on the lunar surface are features.
Fayetteville State University will offer a free telescope observation of the Moon and Evening Sky planets on the evening of September 15 at the university practice football field off Langdon Street in the northeast corner of the campus. Telescopes are set up there and offer a clear view. The session is canceled when the sky is cloudy. For more information, call the FSU Planetarium at 910-672-1759 or 910-672-1926
If you have questions about astronomy, send them back to Backyard Universe, P.O. Box 297, Stedman, NC 28391 or email [email protected]