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The discovery of the Eye of Horus (EoH), a rare double source-plane lenssystem ($z_{\rm lens}=$ 0.795; $z_{\rm src}=$ 1.302 and 1.988), has also led tothe identification of two high-redshift ($z_{\rm phot}\sim$ 0.8) galaxyclusters in the same field based on the subsequent analysis of the Subaru/HyperSuprime-Cam (HSC) optical and XMM-Newton X-ray data. The two brightest clustergalaxies (BCGs), one of which is the lensing galaxy of the EoH, are separatedby only $\sim$100$"$ ($=$ 0.75 Mpc $<$ $r_{200}$) on the sky, raising thepossibility that these two clusters may be physically associated. Here, wepresent a follow-up optical spectroscopic survey of this EoH field, obtaining218 secure redshifts using MMT/Binospec. We have confirmed that there indeedexist two massive ($M_{\rm dyn}$ $>$ $10^{14}$ M$_\odot$) clusters of galaxiesat $z$ $=$ 0.795 (the main cluster) and at $z=0.769$ (the NE cluster). However,these clusters have a velocity offset of $\sim$4300 km s$^{-1}$, suggestingthat this two-cluster system is likely a line-of-sight projection rather than aphysically-related association (e.g., a cluster merger). In terms of theproperties of cluster-member galaxies, these two $z\sim0.8$ clusters appearwell-developed, each harboring an old (age $=$ 3.6-6.0 Gyr) and massive($M_\mathrm{*}$ $=$ 4.2-9.5 $\times$ $10^{11}$ M$_\odot$) BCG and exhibiting awell-established red sequence (RS). This study underscores the importance ofconducting a spectroscopic follow-up for high-redshift cluster candidatesbecause RS-based cluster selections are susceptible to such a projection effectin general.

MMT/Binospec Spectroscopic Survey of Two $z\sim$ 0.8 Galaxy Clusters in the Eye of Horus Field