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moonbuggy
2002-Jan-27, 09:47 PM
Okay I have been lurking long enough.

Question 1. On recently viewing a near full moon with 7 x 25 binoculars I thought I could see slight undulations along the curvature at the edge of the moon's disk. Is this due to earth atmosphere, differences in the colour of the moon surface or can we really see slight differences?

Question 2. Early one morning I was again viewing the moon, this time a slight waning (sp?) crescent, with unassissted vision. I noticed that the dark area of the moon was quite visible and lighter than the surrounding sky. Again was this a trick of the light thanks to earth atmosphere or something else? The dark area was quite noticeable against the black of space - the whole disk of the moon could easily be seen.


Question 3. An easy one, but I have been unable to find the information. Was (is - after all it still exists) the Lunar Rover four-wheel steering? Was it four-wheel drive?


Thanks for the help,
Peter

David Simmons
2002-Jan-27, 10:05 PM
Question 2. Early one morning I was again viewing the moon, this time a slight waning (sp?) crescent, with unassisted vision. I noticed that the dark area of the moon was quite visible and lighter than the surrounding sky. Again was this a trick of the light thanks to earth atmosphere or something else? The dark area was quite noticeable against the black of space - the whole disk of the moon could easily be seen.



Thanks for the help,
Peter


You saw the dark part of the moon by reflected earthlight. This demonstrates that the moon surface can be composed of quite dark rocks and still look bright when illuminated by the sun. Even a small fraction of the earth's reflected light will illuminate the moon enough to be seen against the background of space.

GrapesOfWrath
2002-Jan-27, 11:48 PM
On 2002-01-27 16:47, moonbuggy wrote:
Question 1. On recently viewing a near full moon with 7 x 25 binoculars I thought I could see slight undulations along the curvature at the edge of the moon's disk. Is this due to earth atmosphere, differences in the colour of the moon surface or can we really see slight differences?
I like David's answer to number two. As far as this question is concerned, it sounds like you are actually seeing the variation caused by the shadows of craters. I find them to be visible in 7 x 50 power binoculars, and the moon is bright enough that the smaller aperature wouldn't make much of a difference.

DStahl
2002-Jan-28, 12:35 AM
The rovers had individual electric motors for each of the wheels, and both front and back wheels were steerable, again using electric motors. Excellent site from whence came this info: Nasa lunar rover page (http://nssdc.gsfc.nasa.gov/planetary/lunar/apollo_lrv.html).

Don Stahl

RMallon
2002-Jan-28, 01:16 AM
http://antwrp.gsfc.nasa.gov/apod/ap001228.html

Two cents worth....
I think GofW got the first one right with the terminator line. As I've looked with binocs for years, I've noticed some little undulations at this shadow line along with typical mountain/crater wall shadows. This area of the moon is receiving a low angle of sunlight, hence the heavy contrasts; details emerge. This would also accentuate different terrain altitudes, lending to the wavering effect. The moon is far from having smooth surface features.
Randy

<font size=-1>[ This Message was edited by: RMallon on 2002-01-27 20:25 ]</font>

moonbuggy
2002-Jan-28, 02:01 AM
Okay folks, thanks for the info.

I was thinking about light reflected from earth but forgot to put that in my original post.

RMallon... I think I should try and clarify where I believe I saw the undulated line. It was along the edge of the moon's disk or horizon, if you will, and not along the terminator. The moon was almost full so there was little, if any, terminator to see. Unless the terminator was very close to the edge of the disk, which it always would be in a full moon, but maybe this night it was a little less than perfectly along the horizon - not 100% full.
I will have to keep my eyes open and try again and then repost with some better notes.

DStahl... Great link, that was just what I was looking for.

Peter

photonbucket
2002-Jan-28, 02:12 AM
As I'm new to this site I think I just posted a blank answer, sorry! Anyway, these undulations will be because of surface relief on the Moon and should be particularly evident along the southern edges.

GrapesOfWrath
2002-Jan-28, 02:20 AM
Good one photonbucket, welcome to the BABB. I see you either didn't, or figured out to use the delete post feature.

Weren't the original Galilean telescopes worse than a modern pair of binoculars?

ToSeek
2002-Jan-28, 02:49 PM
On 2002-01-27 20:16, RMallon wrote:
http://antwrp.gsfc.nasa.gov/apod/ap001228.html

Two cents worth....
I think GofW got the first one right with the terminator line. As I've looked with binocs for years, I've noticed some little undulations at this shadow line along with typical mountain/crater wall shadows. This area of the moon is receiving a low angle of sunlight, hence the heavy contrasts; details emerge. This would also accentuate different terrain altitudes, lending to the wavering effect. The moon is far from having smooth surface features.
Randy



The unevenness is also the source of the "Baillie's Beads" (I hope I spelled that right) effect during a total eclipse, when the Sun shines through just a few bits around the edge of the Moon.

GrapesOfWrath
2002-Jan-28, 03:08 PM
On 2002-01-28 09:49, ToSeek wrote:
The unevenness is also the source of the "Baillie's Beads" (I hope I spelled that right)
I don't think anyone knows how to spell it. When I searched for Baily's Beads and Solar Eclipse, I got 365 hits. When I used "Bailey's" instead, I got 221 hits. Uh, Baillie's had none.

Maybe they were looser with orthography back then.

<font size=-1>[And Bailly's had 9 hits--nod to Donnie B. below]</font>

<font size=-1>[ This Message was edited by: GrapesOfWrath on 2002-01-28 12:08 ]</font>

Donnie B.
2002-Jan-28, 05:03 PM
There was a French astronomer named Bailly, has a crater named after him; he's best known for studies of Halley's comet and the Jovian satellites.

However, "Baily's beads" are named after an 18th century British astronomer, Francis Baily.

I don't think there's any "Baillie" associated with lunar studies.

Russ
2002-Jan-28, 11:11 PM
On 2002-01-27 16:47, moonbuggy wrote:


Question 1. On recently viewing a near full moon with 7 x 25 binoculars I thought I could see slight undulations along the curvature at the edge of the moon's disk.

I've got a bit of a whine to toss out here. "undulations" could mean alot of different things.

There are mountains that are visible on the limb of the Moon. These could also cast undulating shadows depending on Sun angle. It could also have been heat convection motion from Earth's atmosphere. It could have been a combination of these. It all depends on what you mean by undulations.

photonbucket
2002-Feb-07, 04:13 PM
Good point but it would have to have been awful seeing in x25 binos.

GrapesOfWrath
2002-Feb-07, 04:21 PM
LOL! I used x24 for a long time, not so bad. 'Course, photonbucket, you don't bend over for anything less than x400, right?

photonbucket
2002-Feb-09, 02:55 PM
Ah Ah, you have totally got the wrong end of the stick. As you increase the magnification and aperture the seeing becomes more and more of a factor-that's what I meant. I used 7x50s and they are fantastic.

GrapesOfWrath
2002-Feb-09, 03:39 PM
Yes, I did misinterpret. Your point was that it would have to be severe seeing conditions in order for it to be a factor in observing undulations on the moon surface through x24 binos. I get it now. Sorry.