*****************************************************************

Week of Oct. 22, 2001

A MOON WATCHER’S GUIDE

(PASTE THIS TO YOUR REFRIGERATOR!)

Many sky watchers derive their greatest observing pleasure from the Moon: the fastest-moving celestial body in our night sky (meteors apart).

You will notice that the Moon’s position changes quite dramatically from one night to the next. If you don’t pay attention, it is easy to lose track of our natural satellite.

Any calendar or almanac will list lunar phases for you, but this listing doesn’t always help when you want to know exactly WHEN you can go out and see the Moon.

Thus, this week we present

THE SOUTHWORTH PLANETARIUM’S

MOON WATCHER GUIDE

We’ll take you step by step through the phases to tell you what you how much of the Moon you can see. It will also tell you what time of night you can actually see the moon during any given phase.

NEW MOON: (CONJUNCTION)

Zero percent of the illuminated Moon half-visible

Moon’s solar elongation angle is 0 degrees

This one is easy. When the Moon is new, it is in the same region of the sky as the Sun and cannot be seen. If you had a bird’s eye view (or spacecraft view) of the Solar System, you’d see the Moon passing between Earth and the Sun.

WAXING CRESCENT:

Less than 50 percent of the illuminated Moon half-visible; Moon’s solar elongation angle is between zero and 90 degrees.

This phase follows New Moon and precedes First Quarter. When the Moon is in the waxing crescent phase, it can be found in the western evening sky. You generally won’t be able to find the Moon until a night or two after the New Moon phase. Even then, it will only appear as a thin crescent enshrouded in evening twilight.

Each successive night, the waxing crescent moon appears to move eastward away from the Sun.

During the latter days of the Waxing Crescent phase, you’ll be able to see the Moon during most of the daylight hours.

FIRST QUARTER MOON. (QUADRATURE)

Fifty percent of the illuminated Moon half-visible

Moon’s solar elongation angle is 90 degrees

Return to that spacecraft view and during the first quarter phase, the Moon would appear to be at a right angle in relation to the Earth-Moon line.

We see the HALF MOON at first quarter. The First Quarter Moon rises around noon in the east and sets around midnight in the west. (These times are approximate, for the rise/set times of the different lunar phases varies with each cycle)

WAXING GIBBOUS:

More than 50 percent but less than 100 percent of the illuminated moon portion visible.

Moon’s solar elongation angle is between 90 and 180 degrees.

The Waxing Gibbous Moon phases precedes FULL MOON.

The waxing gibbous Moon rises in the afternoon as our natural satellite continues to increase its elongation away from the Sun. During the last day or two of this waxing gibbous phase, the Moon appears to be full.

FULL MOON (OPPOSITION)

100 percent of the illuminated Moon portion visible. Moon’s solar elongation angle is 180 degrees

Spacecraft view: Now, the Moon is on the opposite side of Earth with respect to the Sun. We are able to see the entire illuminated Moon. The Full Moon rises around sunset and will remain in the sky until sunrise. (Again, the correlation between moonrise-sunset and moonset-sunrise is not exact.)

WANING GIBBOUS:

Less than 100 percent but more than 50 percent of the illuminated Moon portion visible Moon’s solar elongation angle is between 180 and 90 degrees

The Waning Gibbous Moon follows full moon. Each successive night during the waning gibbous moon phase, the Moon is rising later and later each night: (as a rough rule of thumb, during each night of waning gibbous, add between 40 minutes and one hour to the moonrise time.)

THIRD QUARTER (QUADRATURE)

Fifty percent of the illuminated moon half is visible

Moon’s solar elongation angle is 90 degrees.

The third quarter moon rises around midnight and sets at noon.

WANING CRESCENT

Less than 50 percent of the illuminated moon half is visible.

You’ll see the waning crescent moon in the post midnight and early morning sky. The waning crescent moon will appear as a thin crescent in the pre-dawn a couple of days before NEW MOON. You generally won’t be able to see the Moon during the final day of the waning crescent phase. Of course, at times, you can.

We then return to NEW MOON and the cycle begins anew.

Try this guide for the next few weeks:

The Moon will be at the first quarter point on Oct. 24; will be Full on Nov. 1; last quarter on Nov. 8, new on Nov. 15 and at first quarter again on Nov. 22.

CALL 780-4249 for planetarium show times.

Or, look on our Web site at www.usm.maine.edu/planet

LEAVE A REPLY

Please enter your comment!
Please enter your name here