  Viewing two astronomical sources at large enough distance and angular
separation can assure, by light-travel-time arguments, the acausality of their
emitted photons. Using such photons to set apparatus parameters in a
laboratory-based quantum-mechanical experiment could ensure those switch
settings are independent and fair, allowing a loophole-free test of Bell's
inequality. Quasars are a natural choice for this task, yet at ultimate extent
it involves their simultaneous photometry towards opposite directions on the
sky, which is untried. Cosmic isotropy can be invoked to set limits there,
leaving fairness intact for causal pairs, but with a testable consequence of
asymmetric bias: mean brightness correlations found less flat in sky angle than
random, more acutely so inside a horizon of 90 degrees. Analysis of one dataset
from the Gemini twin telescopes is presented, using over 14 years of archival
broadband-optical images, serendipitously sampling thousands of quasars up to
180 degrees apart. These data reject a null result of no correlation with 97.7%
confidence, instead consistent with a 3-sigma residual signal of 0.21 mag
peaked at 65+/-3 degrees separation. Possible confirmatory observations are
pointed to along with the improved experimental protocol of an Earth-wide test.
