All about size — But what size?

On June 23 this year, Midsummer’s Day as it happens, we’re having an extra full full moon: A Superfull Moon. In fact, at time of writing this, the actual moment of super-fullness happened a good nine and a half hours ago. That doesn’t really matter, because at that time it was well below the horizon where I’m sitting, and won’t rise until a little later in the evening. Not to worry, the difference will be so slight, I won’t even notice. Come to think of it, with the clouds we’re having tonight, I probably won’t even be able to see it.

Good thing that I got a good look at it last year:

Extra full
My camera and I already had a good look at last year’s Supermoon.

Most news sites will tell you that the Moon is amazingly much bigger than usual, to the point where it sounds like you might hit your head on it if you’re not careful. Accompanying photos will give the impression that the Moon will fill half the sky, such as this one which I lifted from the web:

He better watch where he’s running, or he might run into a headache!

A good telephoto lens and a bit of planning and timing is all you need for this. The Moon is still a good 362,570 km away (225,291 miles), though. A mere 21,829 km (13,564 miles) closer than the average, making it some 14% bigger than at its smallest. Mind you, it’s already so little in the sky, 14% of not very much is slightly less than a sixth of not very much, which is … not a whole lot.

Just to give you a clue:

The graphic below represents a 20 degrees wide view of the horizon shortly after moonrise. In the middle is the Moon at its average distance from the Earth. On the right is the Moon at its farthest. The one on the left is the Superfull Moon when the Moon is at its closest to the Earth.

To view it as intended, show the picture as large as possible on the screen (click a suitable one of the links). Then move back until the width of the picture matches the width of your thumb and little finger spread out as far as you can, at arm’s length. This makes the picture about 20 degrees wide to your eyes, and the images of the Moon about half a degree, the same size as they would be in the sky. Can you tell the difference between the moons?

Pick a size: 1920×1080 | 1280×720 | 1024×576

Don’t get me wrong. I love a good moon, half or full, with clouds around or alone in the sky. Another thing is that this occurs about once every fourteen full moons, so if your weather doesn’t allow for decent moon-watching tonight, you may have another go next time 🙂


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