It is the angle between the X-ray direction to the center of the detector and the sample surface. Logically this take-off cannot exceed a maximum of 90°, which is when the X-rays are emitted from a sample perpendicular to the surface (in other words, the detector axis is perpendicular to sample surface).

The take-off angle is the angle from the vertical of a seismic ray as it emerges from the earthquake focus. These angles are calculated from a standard set of tables that describe the relationship between the take-off angle and the distance between the focus and the observing station.

In the case of EDS analysis, "take-off angle" means that the angle at which characteristic X-rays emitted from the specimen are received with a detector placed above the specimen. This angle is defined by the angle of the line connecting the specimen center and the center of the detector against the normal plane to the optical axis.

Other than the collection angle in EDS system, another important parameter is the take-off angle (α). As shown in Figure 4630a, the take-off angle is the angle between the specimen surface (at 0 ° tilt of specimen) and a line to the center of the detector (detector axis).