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


Rilles, Strings, Domes, Mountains, and Craters

David North

There are really only two significant "Moon Events" this month (unless I missed something).

First, around full there will be a strong libration of the eastern limb; this will be best just before the actual full moon on the 21st. If you wait until after full, it will be in shadow!

The moon won't be at its very highest, but that won't matter all that much because you'll be looking for things that don't require great seeing or high magnification: the eastern Maria. In particular Smythii, Australe and Humboldtianum should show you dark patches that usually aren't seen, and the smaller darkenings around Crisium (Anguis et al) should be spectacular rotated around like this.

Even fair Endymion will look more obvious and round than usual.

Also, this is the month that you'll probably get your best looks at the area of Copernicus (just after first quarter, which is on the 14th). This is, of course, the great spectacle of the moon.

Here you can see all manner of the most magnificent rilles, secondary impact strings, domes, mountains and the best defined craters on the moon. Just look near the center of the disk for the next few nights and (weather and seeing permitting) you'll get a shot at what real mooning is all about.

I'm not going to go into great detail about what you should look for. Eventually, you have to strike out on your own, get a reasonable map, and start finding stuff. There's really no substitute.

There was an incredible talk at the January general meeting by Michael Light about his book Full Moon. It is, of course, the wonderful collection of pictures he culled from those shot by astronauts. He cleaned them up a bit, and the results are stunning.

He turns out to be a fascinating speaker. I don't think there was anyone there who wasn't stuck to their seat, fascinated by his talk about the moon and the stories of the astronauts.

I wish I could do that!

One curious problem came up when nobody could figure out for sure what the cover picture was. In the ensuing debate I surely got the answer wrong, didn't hear anything that turned out to be correct, and even the author had the facts a bit muffed.

Turns out the main Maria showing is Mare Smythii. Akkana and I sat around with a globe trying to get the images to mesh, and you can duplicate her feat (she spotted it first) by holding the globe with Smythii toward you and the poles almost horizontal. Then look at the photo, and imagine the lower half (eastern) is dark.

The author's error? He thought it was a picture of the far side, but in fact most of what you see is nearside viewed from a very strange angle, with the wrong stuff foreshortened!

Every time you look you see a different moon.

I wasn't able to see the January eclipse, and since I have to write this at the beginning of February, I have no idea how last month's best nights went - whether we could see Humorum and environs or not.

I hope so.

But don't let that slow you down. There really need be no schedule for when you look at the moon, save for that imposed by the moon itself.

When it's up, look at it!

If it's still in the east at nightfall, wait a bit and it will get higher. If it's near the meridian already, start looking now!

Make sure your scope is out and cooling at sunset, or as soon as possible.

Find the terminator and work your way up and down. See if there's anything interesting - using this approach you don't actually need a map. You can just look.

But if you want to identify your finds, or see where something else might be, or just discuss things with other folks using common terminology, you'll need something.

Rukl's Atlas Of The Moon (usually available at Orion) is best. If you can't get that, head for Akkana Peck's "Hitchhiker's Guide To The Moon" at:

That will get you off on the right foot.

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

Previous | Contents | Next