The WIFD Apochromatic series is part of William Optics’ CAT (Central Axis Tube) design concept, which places the focuser mechanism at the center of the optical tube assembly (OTA), rather than at the rear. This design helps to minimize the effects of flexure and image shift, ensuring a stable and reliable imaging platform. The internal focuser design also eliminates the need for a traditional drawtube, which can cause image shift and vignetting, especially when using heavy cameras and accessories. With the WIFD series, the user can enjoy a smooth and precise focuser within the optical tube assembly (OTA), with no visible movements from the outside. This makes the WIFD series an ideal choice for astrophotographers who demand the highest level of performance and reliability from their equipment.