0.85x Focal Reducer/Corrector for Sky-Watcher BLACK DIAMOND ED120 
Designed for serious Astro-Imagers. Optimized for the Sky-Watcher BLACK DIAMOND ED120, this superb quality accessory effectively reduces the telescope’s focal length by a factor of 0.85x and provides much improved field-edge correction. Use in conjunction with Sky-watcher’s M48 Sony, Canon or Nikon T-ring adaptors.