@dynamicv  
Calling it now: third movie has Principal Luna shift the moon’s orbit, influenced in a way by the Equestrian magics.

@dynamicv
 
Clearly a bug that they will patch in a hot fix.
 
A very hot fix.
 
-Lumino

@PonyPon  
The stars aren’t manual… well besides the Equestrian sun.
 
And even if they are, don’t forget that the moon on the human side isn’t being raised and lowered by a magical sparkling blue moon-butt pony.

@dynamicv  
So it was the manually controlled heavens that dictated the mirror?
 
_{And how did no other pony think of it if it was so simple?}

So Pinkie Pie made a reasonable observation that inspired Twilight to use the link between the two books as a substitute for the lunar/stellar alignment that normally opens the portal?
 
GENIUS!

“What’d ya do with th’ mirror, Twi?”
 
“I took it and turned it into a Starga-”
 
{And then they were sued…}

Twilight Sparkle: Behold, girls! I scienced the fuck out of this mirror and now we can all go to the human world!
 
Spike: Uh, Twilight? I thought the mirror wouldn’t work again for a while. How do we know it will work?
 
Twilight Sparkle: Because I’m Twilight Fucking Sparkle! I could science our way to the human world through a toaster if I wanted to! Now hop in! All of you!
 
Spike: But Twilight!!!
 
Twilight Sparkle: ♪Spi-ike. Tommorrow is experiment night and I still need a guinea pig…♪
 
>Sound of little dragon claws scampering quickly through the mirror.

@Background Pony #8DE0  
They moved it. She’s in charge of it now.

So that thing’s supposed to force open the mirror?  
Didn’t 10 tell her anything about the barrier between universes?

Okay, so the mirror just so happens to be in Twilight’s castle now? Why?