SEPIA optics (in scale). Mirrors CMF1, CMA1, CMF2, CMA2 and Cabin A Instrument switch, NMF1, are part of earlier existing tertiary optics for the APEX multi-channel facility instrument SHeFI and PI instruments of the APEX Cabin A. Mirrors NMA1, NMF2, NMF3 (SEPIA channel switch), NMA2 are parts of the SEPIA dedicated relay optics. Letters A and F in the mirror name indicate active and flat mirrors, respectively. Gaussian beam visualization is done for the lowest ALMA Band 5 RF frequency 158 GHz. The entire relay optics (APEX Cabin A+C+SEPIA) provides frequency independent illumination of the secondary with − 12.5 dB edge taper and was designed to provide the beam clearance and optical element rims at 5ω.