Experimental process:

Important foreword : The LASER power of a LASER pointer is small enough as not to damage the CCD sensor of a camera or its electronics. As a matter of fact its light flux density is much smaller than the SUN shining and burning through your front lens. However this author is not responsible for possible subsequent consequences of the repetition of this experiment by anyone else.

When the LASER pointer is aligned on the optical axis, the LASER ray illuminates the CP990 through the center of the lens. The Aspect Angle is null.
The CCD is then completely saturated by the red LASER and this can be observed on the LCD on the camera itself. A picture shows that effect.

Turning the LASER pointer (even slightly) away from this position shall desaturate the CCD. The picture shown on the LCD is normal. The LASER is shown as a very small red dot.

Move the LASER pointer in front of, but offset from the center Optical Axis of the Fisheye. Then, by slowly rotating the pointer assembly around itself, a specific new position shall produces again saturation of the camera CCD.

Record (protractor) the corresponding Aspect Angle ß between the Optical Axis projection and the line on the ruler by reproduction of the same line on the paper sheet.

The intersection of this line with the Optical Axis is the nodal point for this ß aspect angle.

Repeat this step for various angles on each side of the optical axis from ß0 to ß95deg which is the limit of the lens field-of- view (FOV).

The test result is shown here.