Minmus and tidal lock

[Cykyrios]

So, we all know/think that Minmus is tidally locked to Kerbin, which is mostly true. However, due to the way it is locked (it will face Kerbin but its equator will stay parallel to that of Kerbin, while its orbit is not), libration would make it appear to rotate over the course of its orbit.

From Minmus, Kerbin appears to move in the sky, while it does not when seen from the Mun, which is perfectly tidally locked to Kerbin.

And here\'s a short video showing the movement of Kerbin in Minmus\' sky:

http://youtu.be/2a9-Xgf3joo

[Nooblet68]

This is probably due to Minmus being on a 15* tilt with it\'s orbit.

[PakledHostage]

This is probably due to Minmus being on a 15* tilt with it\'s orbit.

I think that was Cykyrios\' point...

Great video!

P.S. As usual, Wikipedia has a good article on this effect.

Edit: Added link to Wikipedia Analemma article.

[Nooblet68]

I think that was Cykyrios\' point...

Oh, yeah. Sorry Cykyrios; I didn\'t read it properly.

[Cykyrios]

No problem

Ah, analemma, I had already seen this but didn\'t know too much about it, thanks for the link! (though Kerbin only moves along a straight line here)

When other planets are added, there will be some good-looking things, I guess (and we\'ll have to align them all with Kerbol, which turns out to be pretty hard when they are not all in the ecliptic plane).

[PakledHostage]

Ah, analemma, I had already seen this but didn\'t know too much about it, thanks for the link! (though Kerbin only moves along a straight line here)

It only moves along a straight line because Minmus\' orbit is circular. An analemma\'s shape is defined primarily by the eccentricity and obliquity of the observer\'s orbit. Obliquity causes the north-south motion (declination), while eccentricity causes the east-west motion (equation of time).

Sorry if that\'s too much detail... I can\'t help it; I\'m a navigation geek. (I suspect that I\'m the only member of the KSP forum who owns and knows how to use a sextant...)

[Thiel]

(I suspect that I\'m the only member of the KSP forum who owns and knows how to use a sextant...)

As the owner and frequent user of an Celestaire ASTRA IIIB I\'m happy to prove you wrong.

[PakledHostage]

As the owner and frequent user of an Celestaire ASTRA IIIB I\'m happy to prove you wrong.

I\'m happy you\'ve proven me wrong too! I have the same sextant. It’s brilliant.

Now back on topic... Sorry mods.

[Zephram Kerman]

Beautiful video. I find these things fascinating!

I don\'t have a sextant. But, I did stay at a Holiday Inn last night...