Half of an Equation Equals Nothing

Gnomonic, it's
An amazement and an absence,
Unsullied by stained glasses,
Angle in a church hulled over a church,
The subtracted piece of an abstract
Whole. Do with it what you can
Redouble, and rejoice, lovely Anna
Lemma, shadow of the map maker's
Sun, ribbon of time floating
Somewhere over the empty
Pacific, not far from far Easter
Island, a dial for the north's
Passing over painted over the other
Hemisphere, parallel
To whatever was taken
Away.