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The Follow-up telescope (FXT) is one of the instruments on board for the Einstein Probe mission, a dedicated mission to the study of the time-domain high-energy astrophysics due to launch end of 2023. The full calibration tests were carried out at the PANTER X-ray test facility, of the Max-Planck Institute for extraterrestrial Physics in Germany, to validate the performance of the fully flight-compatible optics, both the Qualification Model (QM) and the Flight Model (FM). The eROSITA Wolter-I-type telescope, consisting of 54 X-ray mirror shells was characterised in terms of the angular resolution and effective area. The effective areas were measured using the “Glucksrad” that allows quasi-parallel beam measurements to simulate the in-orbit scenario. The TRoPIC and PIXI detectors were used to take the exposures. A silicon drift detector mounted sidelong in the tube, out of the optic’s field of view, was installed to monitor the X-ray beam simultaneously. The QM telescope experienced a slight degradation of the half energy width (HEW) at Al-K energy (1.49 keV) during the thermal cycle test while the FM satisfied the requirements. Both modules satisfied the effective area requirement at this standard energy. In this work, we discuss the full calibration tests at different energies for the Einstein Probe FXT - QM and FM. The measured HEW, effective area, vignetting, and final focal length at PANTER will be summarized.
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