THE MOON, APRIL 2013
SPECIAL NOTE: Daylight Savings Time (in the US) occurred on March 10 (second Sunday in March). When that happened, local time zones became 1hr closer to UTC (where applicable). Thus, on the east coast, EST (Eastern Standard Time) is now EDT (Eastern Daylight Time) and only 4hrs behind UTC instead of the usual 5hrs behind. I believe Europe hits Daylight Savings Time (called “Summer Time”) on March 31 (last sun of March).
APRIL 1 (Mon) – Entering the month at 0001 UTC on the 1st of April the Moon is 20 days old in the constellation Ophiuchus.
APRIL 1 (Mon) – Moon is at its Greatest Southern Declination of – 20.2 degrees.
APRIL 3 (Wed) – LAST QUARTER MOON occurs at 0437 UTC (0037 EDT).
APRIL 4 (Thurs) – The CURTISS CROSS, an effect of shadows along craters Gambart and Parry which create an “X” shaped illumination will begin to occur at 1237 UTC (0837 EDT). Because of the times this month’s occurs it may well be too light in the US and Europe. The “X” formations occur along the Terminator (where “day” meets “night” along the Moon).
APRIL 5 (Fri) – LATITUDINAL LIBRATION (see definition below) is at MINIMUM of (-6.8 degrees).
APRIL 8 (Mon) – LONGITUDINAL LIBRATION (see definition below) is at MAXIMUM of (+5.1 degrees).
APRIL 7-13 – As of the 7th we are on the verge of the New Moon, this week presents nights that are the absolute BEST nights to get out and observe Deep Sky Objects (DSOs) because you won’t have to look through the spotlight that is the Moon. Night skies without the Moon are significantly more productive for viewing and photography ANY night sky object (besides the Moon itself of course). For the lucky ones, this week offers the amazing spectacle of the extreme Crescent Moon, both waning & waxing.
APRIL 10 (Wed) – NEW MOON (Lunation 1117) will occur at 0939 UTC (0539 EDT).
APRIL (15) – Moon is at greatest northern declination of +20.3 degrees.
APRIL 15 (Mon) – APOGEE MOON occurs at 2223 UTC (1823 EDT) where the Moon is at its furthest point from Earth in its current orbit and will be subtending at 29’ arc minutes from a distance of 404,864km (251,571mi).
APRIL 17 (Wed) – LUNAR-X also known as the PURBACH or WERNER CROSS is scheduled to begin at 2357 UTC (1957 EDT) this should make it easily visible in Europe and in the eastern US but probably tough for the western US. The Lunar-X is the big, more prominent brother to the Curtiss Cross. This “X” is created by the effect of shadows along rims and ridges of craters LaCaille, Blanchinus and Purbach. The “X” formations occur along the Terminator (where “day” meets “night” along the Moon).
APRIL 18 (Thurs) – FIRST QUARTER MOON is the Moon watchers paradise. Occurring at 1232 UTC (0832 EDT), First Quarter Moons and the waxing crescent phase leading up to it offer some of the most visually stunning views the Moon has to offer. Most of us will take the beautiful curves, valleys and shadows of a 1st Quarter Moon over a Full Moon ANY day.
APRIL 20 (Sat) – LATITUDINAL LIBRATION (see definition below) is at MAXIMUM (+6.8 degrees).
APRIL 21(Sun) – LONGITUDINAL LIBRATION (see definition below) is at MINIMUM (-6.6 degrees).
APRIL 25 (Thurs) – FULL PINK MOON occurs at 2000 UTC (1600 EDT) – This name came from the herb moss pink, or wild ground phlox, which is one of the earliest widespread flowers of the spring. Other names for this month’s celestial body include the Full Sprouting Grass Moon, the Egg Moon, and among coastal tribes the Full Fish Moon, because this was the time that the shad swam upstream to spawn.
APRIL 27 (Sat) – PERIGEE MOON occurs at 1953 UTC (1553 EDT) and is when the Moon is at its closest point to Earth in its orbit. It will be subtending at 32’arc minutes from a distance of 362,267km (225,102mi).
APRIL 28 (Sun) – The Moon is once again at its Greatest Southern Declination of -20.2 degrees.
APRIL 30 (Tues) – As the clock strikes midnight, the Moon will exit the month of March at a 19 day old waning-gibbous Moon.
***Definition of LIBRATION (basically) – Is an oscillation of an orbiting body relative to another. OK, so…We know the Earth/Moon system is tidally locked so we always see the same side of the moon. Due to libration, we ACTUALLY see about 60% of the Moon instead of what you may intuitively think of as a 50% measurement. That’s because the Moon oscillates slightly as it rotates and orbits Earth. So, on occasion and with a keen eye we can see a little further “around the corner” north, south, east and west on the moon by a couple degrees.
***SUBTENDING Explained – Definition: The angle formed by an object at a given external point. The moon subtends an angle of approximately 0.54° (32 arc minutes) to an observer on the Earth. Of course, the moon’s orbit is not constant or exactly circular, so this varies a little, but not by very much.
If you hold up your thumb at arm’s length, you can easily cover the full moon. This means your thumb subtends a larger angle to your eye at arm’s length than the moon does at 380,000 kilometers.
In general, the closer you are to a particular object the larger that subtending angle.
NASA Lunar Cycles for 2013