Thursday, October 28, 2010

Another Moon

Another clear night so another Moon photo. But this is no quick and easy post as there were many trials before took this one.

The moon is rising very far to the North at the moment - an explanation at the Natural Navigator site here, though to be honest I can't quite get my head around it so will email Tristan for more.


Tillerman said...

Just think that the rising full moon is always opposite the setting sun. You know the sun sets further to the south in the winter and further to the north in the summer. (If you don't, come and sit on my deck for a year and watch some sunsets.) So naturally as we near the winter solstice the full moon is rising further and further to the north.

JP said...

Hmmmm... yes, but the orbit of the moon is more complicated than that - see:

It is inclined to the plane of the ecliptic in a plane that rotates 360 deg every 18.6 years.

Yes, the full moon is rising as the sun sets but where is not that obvious to me (yet - am still pondering about this)

I might have missed something really obvious though, but predicting the position of the Moon is very complicated (pages and pages of tables containing parameters for equations)

Tillerman said...

Well yeah, it's hard to predict the moon's position for sure. Maybe I'm over simplifying, but if the moon is full, it must be opposite the sun or very close to it, mustn't it? If it were anywhere else it wouldn't be full.

Tillerman said...

Here's another way to think of it. The moon's orbit is tilted from the plane of the ecliptic by about 5 degrees. The earth's axis is tilted from the plane of the ecliptic by about 23 degrees. The movement of the position of sunset with the seasons is caused by that 23 degrees, which also changes the position of rising and setting of all other astronomical bodies.

Not sure what the 5 degree tilt does to affect the position of rising and setting of the moon during the year if at all (I can't get my head around that one), but the 23 degree effect is bound to be bigger than the 5 degree effect.

Verification word: surcul. What planetary orbits are not.

Tillerman said...

And when the moon is new it is close to the sun in the sky so it must rise further south at this time of year. (I think.)

And when they were only half-way up,
They were neither up nor down.

No wait. That's something else.

Carol Anne said...

And there is never such a thing as a completely full moon, since if the sun and earth are perfectly lined up with it, the earth casts a shadow on it, causing an eclipse.

JP said...

Err..... still trying to ponder it. But as Carol Anne says the moon is never exactly full as that would be an eclipse.

So it could appear to be full when rising somewhere in the East as the sun sets in the West whether its slightly north or south of East.

my2fish said...

jp - are you planning to photograph the lunar eclipse (coinciding with the winter solstice - 1st time in 372 years or something like that)??

I thought about it, but it will be really cold, and very early in the morning (for me, anyway).

cheers, my2fish

my2fish said...

I set my alarm for 3AM and woke up to look out the window and see nothing but clouds.

as I laid back down in bed, I thought to myself... if it's 3AM in Michigan, it's daylight across the pond, so it might have been pretty hard to see the lunar eclipse. argh...mental fart.

oh well - I guess we can both Google it now.

cheers, my2fish