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Bad Moon On The Rise

Dave North


If it looks like you’ve had several martinis too many, probably best to forget it for tonight.



This month you'll get an opportunity to see a really bad moon, first hand.

One of the worst, actually.

It will happen June 21, the last day of Spring and the first day of Summer: the Solstice. On that day, the Sun will be highest in the sky for us northerners.

On the other hand, the Moon will be just about as low in the sky as it gets, and further there won't be much darkness (shortest night of the year). That, of course, means we'll probably have completely rotten seeing.

And if that wasn't enough, it will also be only three days short of full, with the terminator just past Mare Humorum, offering a minimum of targets.

And if that isn't enough, since it's getting on to full, the Moon won't even manage to haul itself up to its modest maximum elevation until later in the evening.

So why would I even suggest you check out such a thing?

Well, for one thing it's just kind of fun to get out and look at something on the Solstice. For another, it's a mechanically visible representation of how the orbital dynamics of the Sun and Moon relate to each other.

And if that isn't enough, it's probably going to be warm and pleasant, and you can keep all your lights on while looking at the Moon.

Okay, so maybe there's another minor point: since it's not going to be very good anyway, you can just catch a glance early on and see if you're interested.

This Moon theme is also useful in pointing out that, though the weather is better and there will be more clear nights, this is not going to be a very good season for Moon observing in great detail, since the evening Moon will generally be pretty low in the sky for quite a while.

The best way to approach it is to set up each night, and take a look around sunset (when near the first quarter). We often get our best seeing just as twilight fades to dark — for some reason the air is particularly calm.

Later in the lunation (as we approach full) the Moon will be so low near sunset that it will be hard to get a good look until it's further up. So there you just set up and let stuff sit around until later, then take a glance to see how the seeing is behaving. If it looks like you've had several martinis too many, probably best to forget it for tonight.

But the paradoxical bonus is, sometimes in summer the air just goes dead still for some reason, and even at low elevations you can still get spectacular Mooning nights.

So that's the basic technique for the devoted Moon junkie: check it out every night and soak up what you can when it works well.

It's also fun to note how many times you get clouded out — some years it's fairly surprising how few clear nights we get, even in Summer. If none of that sounds like fun to you, there is another possibility that's actually pretty pleasant. Get any book or decent reference that shows you the larger features on the Moon, and sit down with a nice reading light, your telescope, and make sure you have a comfortable chair.

Look at the items visible and check their names from the chart, and if there are any descriptions, note what you think of the author's impression.

Cherrington's Moon Through Binoculars and Small Telescopes is pretty good for this game.

It will give you a feel for how things relate, how their sizes compare, and what may have been the cause of many objects you see. This is, curiously, best done at lower powers — where poor seeing is not so important. What ever you do, have fun with it. Even people who get paid to look at the Moon seem to enjoy it, so you should too!


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