newbie here asking something about ...

[keeplookingup]

a few things.

hope all is well with everyone.

decided to start watching the moon because it is just so close to us.

I noticed that, maybe, tycho crater appeared to shift to me over the course of a few days. or is it my tired eyes?

I started googling and found someone mentioned this:

Lunar precession

the moon precession is 9 years?

if tycho actually did move do to this .

my questions are:

1. Does tycho ever go non-visible?

2. what objects could I watch that would be unseen for some time and then reappear later during the process

thanks

- newbie

in china we say niu bi but i cant say what it means other than...

its really cool

[oldfruit]

Hi, The moon always has the same side facing us. The moon does sometimes appear to turn slightly during its orbit but the ammount is so slight that i doubt it would be noticable to anyone but the most experienced observers, so must be your tired eyes.

[brianb]

The moon does sometimes appear to turn slightly during its orbit but the ammount is so slight that i doubt it would be noticable to anyone but the most experienced observers

Aw c'mon, it's a very noticeable effect - sometimes e.g. Mare Crisium is well clear of the limb, sometimes it's almost touching; libration in longitude runs up to approx 7 degrees either way and is due to the eccentricity of the lunar orbit; libration in latitude runs up to about 6 degrees either way and is due to the plane of the lunar orbit not coinciding with the earth's equator. There is also a bit of extra libration (up to one degree) caused by the observer (on the earth's surface) not necessarily being on line between the earth's and moon's centres. Altogether we can see almost 59% of the moon's surface, but obviously not more than 50% at any particular moment in time.

Libration effects can easily but accurately be simulated using the excellent, and free, Virtual Lunar Atlas program.

[oldfruit]

Appologies but my inexperienced eyes have seldom noticed the effect though i have read about it. I do feel though that whilst 7 degrees may sound a lot, to the inexperienced observer it would be hard to notice without a lot of time observing the moon.

[Talitha]

No apologies needed. You're absolutely right, casual lunar observers wouldn't recognize librational effects, but we moonatics notice it right away.

António Cidadão made a wonderful one month time-lapse sequence of the Moon which nicely illustrates the rocking motion caused by libration. It may take a while to load depending on your connection, but hang in there.. it's worth it.

APOD - August 10, 2003

[keeplookingup]

precession folks. what happened ?

i noticed it right away.

some nights tycho crater is in one area then seems to move to another after a few days. ive seen photos where the move is obvious. and last night i saw it after watching the moon for a while.

my question is:

precession of the moon.

the earths precession is about 26,000 years? when will Vega be our north star?

the moon appears to have its own and i wonder how large it is and will certain objects

(stated above) someone said mare crisium is close the the limb while other times it is very clear of it.

so that means the moon does actually have its own precession?

im totally new to this and just trying to get an idea of why i noticed something last night.

tired eyes also

haha thanks guys.