The ZWO ADC (Atmospheric Dispersion Corrector) improves your visual observation experience and is still a staple in 2025! Optical dispersion occurs when light passes through the atmosphere, spreading into a spectrum of colors due to its wavelength and the angle of light. The dispersion causes a bluish fringe at the top and a red fringe at the bottom of objects when atmospheric conditions are severe.
This ZWO ADC improves image resolution by applying the opposite amount of dispersion caused by the atmosphere. This adapter has a 1.25” barrel adapter with brass compression rings for a secure connection. Two slots overlap to allow both levers to move together over a wider range to accommodate a changing orientation of the null location (without having to rotate the body). A convenient feature is the white locking screw on the scale marking the horizontal position and the rotatable scale. This allows the null point to be readily seen to set the levers symmetrically on either side and allows you to finely position the null point without having to rotate the body.
The two H-K9L (BK-7 equivalent) prisms in the device each have 2° deviation angles and are said to be of 1/10 wave accuracy.
