Crescent Moon and planets

The Moon on its way out into December’s evening sky passes as many as six planets in as many days (if you count Pluto as a planet).

Sky scene 2016 December 4 evening

The arrows through the planets and Sun show their change of position, against the starry background, over 5 days.

A timetable of the Moon’s appulses (nearest approaches) to the planets:

Nov 30 – 3.6° north of Saturn (only about 9° from the Sun)
Dec  1 – 7.1° north of Mercury (about 18° from the Sun)
Dec  2 – 2.8° north of Pluto (35° from the Sun)
Dec  3 – 5.8° north of Venus (44° from the Sun)
Dec  5 – 2.9° north of Mars (66° from the Sun)
Dec  6 – 0.67° north of Neptune (84° from the Sun)

Those angular distances are as measured from the center of the Moon.  From our northern part of the Earth, the Moon appears somewhat farther south, so the angles are wider.

Only Venus and Mars are bright enough, and far enough from the Sun, to make a showing for the naked eye.

By December 6, the Moon will have sloped down to the ecliptic (it is at its descending node on that day), so the encounter with Neptune is the closest.  Indeed the Moon will occult Neptune, as seen acrpss North America though after sunset only on the northeastern fringes.

Occultation of Neptune 2016 December 6

Detail from the “Occultations” section of Astronomical Calendar 2016, showing very approximately the path from within which Neptune becomes hidden by the Moon.

Somewhere on the website of the International Occultation Timing Association (IOTA) there must surely be a detailed map and predictions of timing for this event, but I have not found it; perhaps someone can point us to it.


6 thoughts on “Crescent Moon and planets”

  1. I made my first sighting of the waxing crescent Moon at sunset yesterday. She was a dramatically thin crescent, only two and a half days old, and quite lovely to the naked eye and through mounted binoculars and a 70 mm f/6 refractor. The telescope at 42x magnification showed the eastern edge of Mare Crisium and four craters on the limb south of Crisium. I forgot to bring my Moon map out with me, I forgot to check it later, and now I’m at work and the map is at home (and I can’t find a decent labeled map online), so I hope to remember to check the map this evening and learn, or re-learn those craters’ names.

    Yesterday was also my first telescopic glimpse of Venus during her current evening apparition. At 42x through a 25% neutral density filter stacked on a polarizing filter, she showed a distinctly gibbous phase. I’m looking forward to following her waning and waxing phases these next few months.

    E pur se muove.

    1. Anthony means that this kind of observing is like reliving the exploratory experience of Galileo. He is said to have murmured “Eppur si muove” (I thought it was spelled like that, perhaps an alternative) as he left the chamber in which he had just been forced to recant his belief that the Earth is a planet that moves around the Sun: “And yet it – the Earth – does move.”

      1. I was writing from memory and I don’t know Italian, so I’m sure you’re right. I thought “E” means “And”.

        1. E, “and” + pur, “yet, though, while”. Italian tends to geminate (double, lengthen) a consonant before a stressed vowel.

          Pur mai non sentesi
          Felice appieno
          Chi su quel seno
          Non liba amore.
          (I expect some opera-lover to correct some of that.)

  2. Thanks for the literal “heads up” on the planet alignments, Guy! If I use a large telescope to see Pluto, then look at my feet, I may see 7 planets!

    1. Gary, after a session of showing folks in the hood the planets in the sky, I ask if they want to see one more, and after a resounding “YES!”,, I tell them to just look down at their feet. Yes, we’re just another one of ’em circling ’round our Sun.

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