  The Earth's Shadow to Cosmic Rays offer a windows to Tau Neutrino Astronomy
at the Horizon edges. Inclined and Horizontal C.R. Showers (70^o-90^o zenith
angle) produce secondary (gamma,e) mostly suppressed by high column atmosphere
depth. The shower Cherenkov photons are diluted and filtered by air opacity,
but secondary penetrating, muon pairs and their decay into electron pairs,
revive additional Cerenkov flash lights. Most largest GeVs gamma telescopes may
detect such UHECR horizontal showers. Arrival angle and column depth, shower
shape, timing may inform on the altitude interaction and on primary UHECR
composition. At larger zenith angle (90^o-99^o) more rare up-going showers are
traced by muon (as well electromagnetic) bundles that would give evidence of
rare Earth-Skimming neutrinos, tau and anti-tau neutrinos, at PeVs-EeVs
energies. Their rate may be comparable with 6.3 PeVs anti-neutrino electron
induced air-shower originated in interposed atmosphere, by W^- resonance at
Glashow peak. Additional and complementary UHE SUSY neutralino or staus may
blaze. Their nature might be disentangled by Stereoscopic Telescopes array.
Magic and Hess telescope in present set up may be already comparable to AMANDA
underground neutrino detector. Such telescopes pointing at the horizons toward
active sources (AGN,BL Lac Objects, GRBs or SGRs blazing micro-quasar jet, and
SNRs) do experience in those directions an air mass corresponding to a km^3
water one. Therefore Horizontal Showering is already the most sensitive windows
to Neutrino Astronomy possibly pointing to AGN,GRB or SGR events.
