Selective electron beam melting (SEBM) is a powder-bed based additive manufacturing technology which allows to process the non-weldable superalloy CMSX-4 into single crystals (SX) using specific process strategies. These additively manufactured SX of remarkably high homogeneity show improved creep and high-temperature strength, fatigue life or oxidation resistance.  The process window of CMSX-4 and the underlying SX selection mechanism are well understood. However, for building complex parts, conventional SEBM-machines lack the required process controllability by continuous in-situ imaging. For this purpose, multiple researchers propose a novel SEBM-cycle with electron-optical (ELO) imaging by detecting backscattered electrons after an additional scan of the build area. In the present study, ELO imaging is successfully demonstrated under the harsh process conditions of CMSX-4 at build temperatures of roughly 1000°C for almost 30 hours. Different imaging modes are used for optimized process control by monitoring surface features like pits or cracks.