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How To Look At The Moon

Dave North

December is a good time to give a quick overview of How To View The Moon. Why?

Some of you will have just acquired new toys and be curious how best to use them. Others will be kept nearer to home by the weather, where dark skies are hard to find.

But best of all, December is when the tide turns and Moon Season starts up - the half of the year when the Moon is best viewed in the evening.

It doesn't hurt that the sun sets earlier, so there's more dark time ... but the real point is the Moon will be higher in the sky between now and June (basically) with the high point late in the cycle now (near full) and moving toward first quarter around March or April.

New telescopes, especially those with good optics, can cut their teeth very nicely on the Moon.

Sure, Jupiter and Saturn are up there (and you absolutely should spend time with them), but there just isn't an object as "telescope friendly" as the moon.

It has hard edges on the shadows of mountains and craters, and this creates practically the maximum contrast aside from a star against a black background.

Contrast is a good thing, especially to scopes with central obstructions (such as Newtonians and catadioptrics: SCTs, Maks, etc). The secondary mirror cuts contrast a hair, and having strong contrast in the image itself is a real plus.

More detail can be seen on the moon than any other celestial object, save perhaps the Sun with some very expensive equipment. For most of us, that means the Moon is the obvious starting point.

First, the issue of filters: you don't need any.

No doubt you'll try a low-power view at first, and that might prove to be pretty bright. But in the long run, you'll find the high-power views are most satisfying, and they cut some of the glare.

Then, you start working the terminator (the zone of high shadows where the "lit" side of the moon meets the "dark" side). Here the reflected light is not very bright at all, and you'll find it reasonably comfortable in just about any scope (I run my 12.5-inch wide open like this regularly, and have used the 30-inch at Fremont Peak full bore ... for those who have doubts about this, I just got my eyes tested last week and my doctor says they are still exceptionally sharp. So don't sweat it).

What kind of scope? Any kind! That's one of the great things about the Moon. From smallest to largest, you'll get something worthwhile (though seeing can be an issue if you're packing an 18-inch or so -you might want to consider an off-axis mask for "nervous nights."

Anything smaller, just point and shoot.

I find the useful magnification range runs between 125x to 400x fairly often, with the most typical views between 180x and 225x due to seeing pains. If your eyepieces work that range adequately, you're okay for now.

This being winter, consider eyepieces with fairly significant eye relief. I find the moisture from my eye tends to fog up eye lenses when I get too close to them - this is not much of a problem in summer.

Books? There aren't any "ideal" maps, and I find most of them frustrating due to the reference numbers or other weird labeling systems.

In the long run, Antonin Rukl's Atlas of The Moon (under whatever publishing rubric you find it) is the best overall. And for more general finding, a Moon Globe is an unbeatable aid.

But any rough chart will work at first - when I started "mooning," I hated all the maps so much that I traced one out and labeled it myself. With your computer, you can probably make this project a little simpler if you decide to duplicate my effort.

If you do, publish!

I think it's best to start by memorizing a few major features, particularly Mare Crisium, Mare Nectaris, Mare Imbrium, Clavius, Tycho, Ptolemaeus, and Mare Humorum.

I know you'll find Mare Tranquilitatis - who could resist?

If you have just these landmarks down, you'll be able to navigate to less familiar places ... so let that be your first project, after the obvious one:

Just looking.

If you are a new telescope owner, and don't know what they can do yet, there are at least four experiences that will be completely unforgettable:

Your first view of the Moon (unbelievable detail), your first view of Saturn (is that real?) your first view of Jupiter (you can see the bands and moons?!) and M42 (what, deep sky? Yup).

And of course, there will be more. But don't forget your first best friend ... the Moon.

Mail to: Dave North
Copyright © 2000 San Jose Astronomical Association
Last updated: July 19, 2007

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