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Mooning

New Moon

Dave North


Old folks in the astronomy world can tell you it happens just about this time every year: a flood of new telescopes, often owned by the newly star-bitten who are still trying to figure out the basics, find some place to go observing, figure out what kind of eyepiece they really need, how to adjust this or that...

Usually it's Santa's fault, but he ain't going to come by to show you how all this stuff works, so it's up to us to take up the slack.

Let me cut to the chase: point it at the Moon.

This avoids many of the problems you'll run into with other targets.

For one thing, light pollution (what's that? Wasted light blowing up into the sky, that's what) won't wash it out.

It's very easy to find, except when you can't find it at all.

And it will give a tremendous, detailed view in just about any telescope (except the very worst, where it will still give about the best view possible, but it may turn out that what's possible just isn't good enough. Can't help you there).

Every answer raises another question, though. What did I mean by "when you can't find it at all?"

The Moon is visible on the same basic principal as the Sun: you can see it when our side of the earth is facing it, and you can't when we're not. The schedule may be different, but the idea is the same.

Sometimes, from our point of view, it's night with respect to the Moon, too.

This means you won't be able to just pop out any time you want to look at it, any more than you'll have much luck seeing Scorpius right now. For some things, you have to learn the schedule.

This month is going to be a tad frustrating at first. We start it just past full, which means it won't even be rising until after sunset, and won't get high enough for viewing until midnight or so. And that situation will get worse as time goes by.

In fact, you'll soon find the best time to see it is actually early in the morning. If you're like me, though, there is no early in the morning, so it will be later a couple of weeks before you can really get into full swing.

Just about the ides of January, to be exact.

On the other hand, we've been a little behind getting the Ephemeris into the mail lately, and there will have been the usual Post Office Panic at the same time, so the odds are that isn't all that too far away as you read this.

If you start on the fifteenth (and weather permits) you'll have a short night. The Moon will be setting as night falls, and you'll see a nifty little crescent with a fat helping of earthshine in the bowl.

You've heard of moonshine, but earthshine? Yup, it's the reflection of the earth projected onto the Dark Side Of The Moon, lighting it enough to make it stand out from the True Dark Of Space behind it.

If you look closely, you'll be able to see some darker spots in the earthshine - those are Maria, or the dusky "seas" of the Moon. Okay, they're actually massive basaltic flows, but let's not get too technical just yet.

These nights early in the lunation are in some ways the best kind of New Telescope (or even Old, Lazy Telescope) viewing.

Why? For one thing, you won't be out long. For another, anything low in the sky is more affected by Bad Air than things higher up, so you won't be able to do any high-power observing.

What's so good about that? It means any old average eyepiece and telescope will give you a spectacular view of this lowdown Moon. Finding, focusing and tracking are very easy, and your tube will probably be nicely aligned for sitting and pondering a bit.

Another good thing is, there just aren't that many features visible. So if you have a decent map, globe or reference, you can get familiar with some of the easier eastern features without a lot of other Moon to complicate and confuse.

Like most people, you'll probably cop to Mare Crisium first, and perhaps go on to learn Langrenus and Friends, and maybe a few other things.

After that, as each night progresses, you'll be able to look a little longer, pick up a few more names and locations, and find your way around.

Also, as time goes by and you get familiar with your equipment (and the Moon gets higher in the sky, out of that Bad Air We Breathe) you'll be able to use More Power, Captain.

In the long run, that will be the name of the game: power. Getting a real taste for the Moon will require magnification, so you can see all those nifty little things are are just hinted at by low-power gazing.

Which means the Moon is friendly to new scopes in many ways, not the least of which is it introduces itself politely and gives you a chance to get to know it.

The First Big Tip: to see detail, hunt the terminator. And no, I don't mean Arnold. The "terminator" is luno-techno-speak for the line where light meets darkness. A little logic will tell you that's also the area of long shadows, right?

Shadows are your friend when looking at the Moon. It doesn't have much in the way of color contrast, so the best feature contrast is generated when one side is lit and the other dark - it will look at first as if it were an impossibly pearly white and a deep, endless black. But after a while, you'll be able to pick out the rich greyscales involved.

I should mention two things more: an upside and a downside.

The upside is, this time of year the interesting parts of the Moon will be well lit when it's higher in the sky than in summer, so there will be less turbulent air to look through. So when you get a calm, clear night you stand a chance to really crank up your power and get a look at some amazing detail over a quarter of a million miles away.

The downside is, the weather will probably fight you. It may rain, it may be windy, or it may be horribly cold. The good part of Moon observing, however, is the last may not matter much. You can get fine views right from your back yard, and keep a warming device handy (electric blanket, hair dryer, spouse, whatever).

Oh, one last thing. You'll hear from some supposed experts that the Moon is "too bright to look at through a telescope" and might "burn your eyes."

This is the worst sort of idiocy: can't happen. I won't go into scientific proofs right now, I'll just tell you I've looked at the Moon through scopes up to 60-inches with no difficulty.

You may find (if you get dark adapted by accident) that the view can be uncomfortable, particularly at lower powers. This is the same effect you get when walking out of a dark theater to the sunlight - not dangerous, but bothersome.

There are two easy ways to avoid this.

First, use higher powers. This will "dim down" the image and make it more comfortable. If that's not practical, the other possibility is actually fun ... and sinful!

Turn on a light! Use a nice, bright light to read your charts by. That will keep you from getting dark adapted, and you might actually find you have to turn the light down because the image in the eyepiece is getting too dim.

Give it a shot. Everybody is stunned by their first telescopic images of the Moon, but if you approach it right, you may find that surprise and wonder can last a lifetime.


Mail to: David North
Copyright © 2002 San Jose Astronomical Association
Last updated: July 19, 2007

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