Moonwatching

I was driving home from work a day or two ago, and I noticed the newly risen moon in my rear-view mirror.  I was trying to decide how close it was to being full, and also trying to stop paying attention to the (beautiful) moon in my mirror and look at the (boring) traffic on the highway in front of me.

I’m used to enjoying the beauty of the sunset during my drive home (only during some times of year, of course), but I don’t often see the moon rising. For a moment it threw me that I was seeing it, then I reminded myself that I was driving west but seeing the eastern sky in my rearview mirror.

That got me thinking about how to figure out when to look for the moon and where in the sky, and about the phases of the moon in general. I have a fairly long commute (at least forty-five to fifty minutes, depending on traffic), so I had plenty of time trying to construct diagrams in my head.

I understand how the different phases work in terms of the relative positions of earth, moon, and sun, in terms of how much and which part of the moon is illuminated, but I never remember how to factor in time of day. And the one thing I just couldn’t make sense of, in my mental diagrams, was the new moon.

Calendars show the new moon as a dark circle, since that is when there is no sunlight reflected off the side of the moon facing us. But that means the other side is facing the sun, and therefore as we look at the dark side we’re facing the sun … which means it’s daylight. How could we see that it’s a new moon, if we can’t see it because the sun is so bright?

I figured I must have things mixed up in my head somehow. So I googled the whole subject to find some diagrams better than the ones I could construct in my head while driving, and an explanation about seeing the new moon.

Well, I was right about not seeing the new moon. I guess we know it’s a new moon precisely because we can’t see even a glimpse of a crescent moon, as we can a few days before and after. And the night at that point in the month is moonless, not because the moon is a dark circle, but because the moon is not in the night sky at all, only in the day sky.

But of course a diagram still is helpful, especially for a visually oriented person like me. The one I found most helpful is this interactive one, which lets you see both how the movement of the moon relative to both the earth and sun affects how we see it, and simultaneously an example of how the sky looks to a viewer on earth, over the course of the entire lunar cycle.

It displays both a calendar and a clock, and you can pause the time or move it to a particular day and time. So if I want to see a crescent moon, I can move backward or forward from the new moon to see what time of day and where in the sky to look.

As it happens, there is a website telling people where and when to look for the new crescent moon at the end of this month, and encouraging them to report their observations. As it will apparently be February 1 that it will become visible where I live, I won’t be driving home from work that day (it’s a Saturday), but if I remember I will try to go check for the crescent moon.

If the weather is any more cooperative than it was for viewing the northern lights recently, that is.

 

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