Takahashi 65D FU Reducer 0.65X for Takahashi FCT-65D telescope

Dedicated 0.65x RD-FU reducer for the FCT-65D telescope. New FU reducer series incorporates FLUORITE lens elements for highest performance possible. It is necessary to have #18. 65D FU Reducer 0.65× (TKA11580F) and the #19. CA-35 (FURD) spacing ring in order to image.

The Takahashi FU RD focal reducer is the ultimate tool for deep sky imaging with the Takahashi FCT-65D telescope. It reduces the focal length of the telescope to 260 mm (F4). The instrument then becomes the equivalent of a very high quality fluorite telephoto lens. On a APS-C format chip, the covered field is around 5° x 3.5°. It reaches almost 8° x 5.5° on a sensor in full-frame format! The nebulae of Orion (M42) and the horse head (IC434) in the same field or the entirety of the lace of the swan, with an unequaled dive and contrast.

An original design

Usually Takahashi uses the artificial fluorite crystal (CAF2) for its glasses targets. For the first time, the Japanese company adopted it in the design of one of its optical accessories. The goal is to optimize the performance of the objective/reducing association as part of imaging with sensors with small pixels.

The FU reducer is made up of 4 lenses, one in fluorite, divided into 4 groups. Due to his design, it fits into the focus tube, which reduces flex and imbalances in the entire optical tube. The reduction coefficient is 0.65x; The FCT-65D focal length of 400 mm (f/D 6.2) to 260 mm (f/D 4).

As shown in the curve of the size of the RMS spot, the chromatic aberration is perfectly corrected, even on the edge of the field. The same goes for field curvature. The spot radius is approximately 1.5 µm on the optical axis and 2.5 µm in the extreme periphery of coverage in the APN format (24x36).

Attention ! Even if the three models of FU reducer (65D, 60CP and 76DP) seem to have the same appearance, their optical design is different. Each model is optimized for a type of telescope lens in order to best reduce its optical aberrations. Use an unsuitable reducer will significantly reduce performance.

Connecting the FU reducer to the FCT-65D

A specific CA-35 photo adapter is supplied with the FU RD reducer. For convenience, it is delivered already screwed to the reducer but it must be removed before doing the final assembly. The 56mm classic back focus is obtained by adding the rotary photo frame necklace (CAA-S, delivered with the FCT-65D telescope) then the CA-35 FURD photo adapter (delivered with the reducer) at the back of the focal reducer. The mechanical output is a male thread M52x075.