The Last Quarter Moon of January 27 will be about as high north of the ecliptic as it can get. You can see why, in this detail from our Zodiac Wavy Chart for 2019.
See the end note about enlarging these diagrams.
The blue line is the ecliptic, curved in this projection in which the celestial equator – the red line – is straight.
On January 21, ascending node through the ecliptic coincided with Full Moon, so ther was a total lunar eclipse. Descending node on February 3 will come close to New Moon – though not as close as on January 6, when there was a partial solar eclipse. Half way between, at Last Quarter on Jan. 27, the Moon is at the top of its arch, about 5° (its orbital inclination) north of the ecliptic.
A result of this is that the libration is at a maximum for the year. This is interesting though, as we’ll explain, of limited observational advantage. Libration is the Moon’s apparent “rocking,” caused by its slightly inclined and elliptical orbit. It’s indicated in our chart by a red tab on the Moon’s limb (edge). The tab is at the part of the limb where libration allows us to see farthest into the Moon’s usually invisible far side. The libration maximum is at Jan. 27, 17h Universal time, about 3 hours before the Last Quarter instant, and the amount of libration is a little over 10°. The libration point has to be on the part of the Moon toward the ecliptic; from the ecliptic plane we are now looking slightly northward toward the Moon, so we see more at its southern limb.
Unfortunately the point is on the un-sunlit half of the Last Quarter Moon. So we can’t see past that part of the limb into luna incognita, the “unknown Moon.” But it’s not far from the Moon’s south pole. Therefore, a little to the left, where the sunlit half begins, it might be possible to see a little way into the mostly hidden South-Pole-Aitken Basin, where China’s Chang’e 4 lander is now exploring.
The libration continues approximately the same for several days, as the tabs show.
To see a Last Quarter Moon, you have to be looking after it rises around midnight. Better to be later than that, in the pre-dawn hours. The Moon is then higher, and risen behind it are the stars and planets it is going to pass in the next few dawns – Antares, Jupiter, Venus, Saturn.
As I was writing this, at about six this morning, I opened the window shutters beside me and saw in a black gap between roofs a light so brilliant that I almost thought the town cinema was on fire again – it was the Moon, a day before Last Quarter.
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DIAGRAMS in these posts are made with precision but have to be inserted in another format. You may be able to enlarge them on your monitor. One way: right-click, and choose “View image” Or choose “Copy image”, then put it on your desktop, then open it. On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping with three fingers). I am grateful to know of what methods work for you.
Right click and view image works. then use contl + to fill screen….thanks
We’ve had clear weather since a few hours *after* the lunar eclipse, so for the past six mornings I’ve been able to watch the Moon wane from full to barely gibbous as she sailed south toward and now past the equator. Movement relative to the ecliptic is more subtle, but the Moon passed a bit north of Regulus, and this morning she was pretty far north of Spica.
A few years ago I had an aha moment when I realized that the Moon’s north-south libration is analogous to the Earth’s seasons, and the Moon’s east-west libration is analogous to Earth’s equation of time. I enjoy looking at the Moon through binoculars or a small telescope at low magnification, so I don’t hunt down obscure craters that are barely revealed by libration. But I enjoy seeing how the maria move closer and farther to the Moon’s limb, and looking for the smaller maria close to the limb that are exposed by libration.
Those are insights worth adding to any chapter on libration!!
Thank you!
Thank you. Always have enjoyed understanding the magic of cosmic motion through your perspective and illustrations.
Spreading two fingers on an iPad Pro works great. Terrific diagrams and explanations as usual. Thanks!