September 2014

Tony Martinez

                                    Tony Martinez

Each month I will describe sights of interest in the night skies of South Carolina. These sights will be broken down into three sections; what you can see with the naked eye, with binoculars, and with a small telescope. The best time to view the night sky is at and around the times when the Moon is not visible, what is known as a New Moon; which will occur this month on September 24. For September, your best viewing nights will be from September 15 to the 30. The Star chart below is set for Florence, SC on September 15 at 9 pm.


Lunar Observing:
For many years on my wall calendar I had black dots on at least one day of each month marking the dates of each New Moon. As an amateur astronomer, I used these dates to plan for astronomy viewing trips. My targets of choice were deep sky objects (DSO’s), usually Messier objects, and these faint fuzzy objects are difficult to view when the Moon is in the sky. As you notice every month in the introduction above, I give the best viewing dates based on the phases of the Moon.  This month I would like to discuss the Moon as a target and not a bothersome light in the sky.

Let us begin with the basics. I am always amazed that most people think the best time to view the Moon is when it is full. Actually, the full Moon is the worst time to enjoy observing. The Moon’s intense bright light overpowers your telescope. This brightness can be corrected somewhat by placing a Moon filter into the back of your eyepiece. These filters essentially act like polarized sunglasses, and you can now comfortably look at the full Moon. However, the Moon still lacks texture, or depth; the surface looks flat and drab like a standard black and white photograph. In the image below, left is unfiltered, and right is through a lunar filter.

01What the full Moon is missing is shadows. It is the shadows that define the depth of the craters and the heights of the mountains.

To enjoy observation of the Moon with your telescope you should use the following approach. The best time to look at the Moon with any telescope is from waxing crescent to first quarter. Allow me to digress and discuss the lunar phases. As the Moon phases increase toward the full Moon we say that the Moon is waxing. As the Moon phases decrease from full toward new Moon, we say the Moon is waning.  When the Moon first appears in the west, it is called a waxing crescent.  As the days progress, it reaches the phase called first quarter.  Between first quarter and full, the phases are called waxing gibbous.  After the full Moon it moves into waning gibbous until it reaches third quarter, and finally it moves through waning crescent until it reaches new Moon. Most amateur astronomers do not discuss the various phases of the Moon. Instead we measure the Moon by days. Scientists prefer to use numerical data when describing various events.  Example: A four-day Moon is in crescent in the west. A seven-day Moon is in first quarter. An eight to thirteen-day Moon is in waxing gibbous, etc.

I like to ask students the following questions: Where does the Sun rise and where does it set? Answer: It rises in the east and sets in the west. Now, where does the Moon rise and where does it set? This is not a simple question, so here is the complex answer. After a new Moon, the Moon does not rise, but it just appears low in the west, and then quickly sets in the west. Each night the Moon does not rise, but just appears in the sky farther east each night, and sets later and later in the west. At full Moon, the Moon rises in the east at sunset and sets in the west at sunrise. After the full Moon, the Moon rises every night in the east later and later, but it never sets. To summarize: After a new Moon, the Moon doesn’t rise but always sets. At full Moon the Moon rises and sets. After full Moon the Moon always rises but never sets.

Now, returning to my comments about lunar observation; the best time to observe the Moon through your telescope is between a three day and a seven day Moon. During this period, the Sun casts stark shadows, and the surface features are beautiful to see. Both the craters and the mountains show obvious depth. Below on the left is a five-day Moon as seen through large binoculars or a low power telescope. On the right is a six-day Moon with various lunar features labeled.

02If you develop an interest in lunar observing, you can find many sites on the Internet that will help you identify the many craters and mountain ranges.

Another good aspect of lunar observation, versus planets or deep sky objects, is that you can crank up the power on your telescope, and still have decent resolution. The images below represent the views of craters and a mountain range as seen through ScienceSouth’s ten-inch Dobsonian reflector at about 150 power.

03Finally, the next time you look at the Moon, try using your digital camera as a simple telescope to photograph the Moon. Most simple digital cameras have a significant zoom lens. I took the photo below with a simple handheld point and shoot camera. I am sure you can do much better. Don’t forget you can then improve the contrast using any standard photo editor.


Naked Eye Sights: The Moon.

Binocular Sights (7 to 10 power): The Moon through the first 10 days after New Moon.

Telescope Sights (60-100mm): The Moon through the first 10 days after New Moon. Concentrate on various craters and mountain ranges as they move into view each day.

See you next month!

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