The Moon will swing through the last-quarter point of its orbit on Monday June 8, at 10 by Universal Time.
Here is the pre-dawn scene for an American location, close to the exact time of the last-quarter phase.
See the end note about enlarging illustrations. An arrow through a moving body shows its movement (against the starry background) from 2 days earlier to 2 days later. Saturn is exaggerated 150 times in size, to show the current attitude of its rings. The Moon is exaggerated 4 times in size. It is shown at its apparent position for the location on Earth, displaced by parallax; the arrows are along its path as seen from the center of the Earth.
In the twilight sky, you aren’t likely to see stars or planets dimmer than Mars, Saturn, and Fomalhaut, but it’s worth having a sense of which part of the celestial realm you’re looking at.
And notice “Earth’s direction of travel,” which I mark with a symbol like a steering-wheel. We are driving toward that place where the Moon at this moment is.
As shown in the “Moon’s orbit” and “Moon as Signpost” sections of the Astronomical Companion: the Moon at its first-quarter phase is crossing Earth’s orbit outward, behind us, therefore is seen from the evening side of Earth; at last quarter, it is crossing inward, ahead of us, therefore seen from the morning side.
The first-quarter moment two weeks ago happened to coincide rather closely with a node passage, that is, one of the moments when the Moon slides through the ecliptic plane; which was why we discussed it. Fred Schaaf had pointed out that this is when we can truly say that Earth will be at that point, rather than above or below it.
On that occasion, there was a lapse of only about 4 hours from first quarter to the descending node. This time, the interval from ascending node to last quarter is more than a day, nearly 28 hours. This is shown, if you look carefully, at the arrows in our sky scene, which represent the Moon’s movement corrected for parallax.
One of the closes of these phase-node “Schaaf effect” coincidences will come on November 17. I hope before then to prepare an Astronomical Miscellany” page about the topic.
Earthlight department
Though I had the chance to talk for hours with Freeman Dyson, I didn’t make a sketch of him, probably because he was sitting too close in front of me and I couldn’t attempt it in my surreptitious way. But here is my quick portrait (on a library catalogue-dividing card) of another influential thinker who, like Dyson, died in 1988: Caleb Gattegno.
He was an introducer of imaginative new approaches in education. He must have visited, about 1968, the Navajo school at Rough Rock in Arizona, where I was supposed to be in charge of “TESL,” the teaching of English as a second language, and also of the school’s library. I have no note about him from that time, only that Miranda, aged five and addicted to reading, “was discovered in semi-darkness in her parents’ bedroom, reading The Teaching of English as a Second Language by Gattegno.”
__________
This weblog maintains its right to be about astronomy or anything under the sun.
ILLUSTRATIONS 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 ”Open image in new tab”, then enlarge. 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 and dragging with three fingers). Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.
Sometimes I make improvements or corrections to a post after publishing it. If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version. Or, if you click ‘Refresh’ or press function key 5, you’ll see the version change to the latest.