Specific to the TOA-130F and TOA-150 refractors, the 645-RD reducer is simply an optical piece of art, as only Takahashi can conceive some. On the TOA-150, it reduces the focal length of 1100mm (F/7.3) to 840mm (F/5.6). The deep-sky wide-field astrophotographers will make this accessory as a first choice.