SJAA Ephemeris January 2000 | SJAA Home | Contents | Previous | Next

Mooning

David North


Eclipse!

Not only that, high in the sky, at a good time, with clear air! If the weather holds, this will be about as good as you can hope for.

The first hints of duskiness will appear at around 6pm [Thursday, January 20, 2000], when the moon is low and darkness has barely set in.

Just a little after 7pm, the inkiest part of the earth's shadow should start to creep across the Moon.

At that point, it will be about 20 degrees elevation - not bad.

Over most of the next hour, the shadow will travel across the Moon until it's completely eclipsed a little before eight.

By then, it will be 30 degrees up in the east, and getting out of the thicker atmosphere: colors will be more accurate.

Keep some coffee and maybe popcorn handy, because this will be a long one - about 90 minutes!

Near the end, it will be almost 50 degrees elevation, which is pretty darn good.

And when it gets all the way out of the umbra almost an hour later, elevation will approach 60 degrees.

Another half hour for the penumbra to drift off, and the show's over, but the moon is now near 65 degrees up.

But all this timeline stuff is hardly necessary: the simple approach is to set up around sunset and watch what happens. You can't miss it!

So, what will you need?

Not much. In fact, the less the better.

First, you'll want to see the color. There's no telling what shades will show up, but whatever it is (yellowish, reddish, greenish or even toward the blue) it's spectacular.

However, the best way to see it is usually binoculars. A mount is nice (tripod and bracket, or more elaborate if you can).

The more you can concentrate the light, the better. This means low mag and big aperture - it's one of those rare times when 7x50s might be better than 10x50.

You won't have much use for high mag in any event. The shadow traveling across the moon won't give a sharp terminator like we usually see, so details will be fleeting at best.

In fact, near an eclipse is when one of my silly platitudes fails: There's Always A Terminator. Not when the Sun is directly behind you!

A medium telescopic view might be a plus, just for the fun of it, but don't expect too much - and make sure you have your binos (or Short Tubes or anything like that) primed and ready.

I'm going to experiment with a larger scope, just to see what happens, but in the past the 12.5-inch hasn't been all that great. We'll see.

You might pay particular attention to the leading and trailing edges of the umbra. There, it's often possible to see odd colors due to the effect of our atmosphere on the diffuse light at the edge. All manner of strangeness has been reported in the past.

Another fun pastime is checking out stars being occulted; they're pretty easy when the moon isn't so bright.

And another favorite pastime is wandering through your favorite dark sky objects during the full Moon! Even I have fallen prey to this obtuse indulgence...

What location is best? Well, if you want to see dark sky sights, you'll need a dark sky location. But for the eclipse itself, nothing could be easier.

You won't need seeing, and darkness will only be marginally useful. Basically, anyplace where you don't have bright lights in your eyes should be fine.

Darkness might help a little with color vision, but you can get most of the same advantage just by covering your head with a black cloth, or otherwise blocking the local light.

After the show's over, you might take a crack at some ray tracing (use a moon filter) if you want to keep going; this will be a high moon.

In general, this is the beginning of Evening Moon Season.

During the days just before full moon, elevations will be very high.

That means good seeing, particularly when the terminator is crossing the area of Mare Humorum or Schroter's Valley, two of the most spectacular areas on the moon.

Be there or be square!

One final note: when I was mulling over the question of who I know that might know most (or all, or even a heck of a lot) of the named features on the moon, I somehow forgot the obvious:

Our own Robert Garfinkle!

Most people think of him as a dark sky guy (the observer's classic book Star Hopping, of course) but he's been working on a book about lunar observation for about 100 years now. No book yet, but he does know just about every name there is...

So, in the Moon Scholarship department, things aren't quite as grim as I suspected...


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

Previous | Next