Takahashi Multi-Reducer 0.85x-M for FCT-65D / FC-50

Product Overview

The M version of Takahashi's 0.85x Multi-Reducer, matched to the FCT-65D and FC-50. On the FCT-65D it gives 340 mm at f/5.2; on the FC-50, 340 mm at f/6.8. The image circle is Ø44 mm, which covers a full-frame sensor.

The Multi-Reducer comes in three versions, and the letter is not a size preference — it identifies which telescope family the reducer is computed for. M is the FCT-65D and FC-50; S is the FS-60 series; L is the FC-76 and FC-60/65 series.

Who It's For

This is a good match if you image with an FCT-65D and want the matched reducer — the one Takahashi computed for that tube.

Key Features & Design

• 340 mm at f/5.2 on the FCT-65D: the configuration this version is built around.
• Ø44 mm image circle: covers a full-frame sensor.
• Four elements in three groups: reduces and flattens together.
• M55.9 (P=0.75) telescope side, M52 (P=0.75) camera side.
• Ø60 × 54.7 mm, approx. 215 g.

Optical / Mechanical Design

A 0.85x reduction takes 15% off the focal length and speeds the focal ratio to match — modest next to a 0.6x or 0.7x reducer, and one that keeps image scale usable rather than collapsing it. The four-element, three-group design is what holds the Ø44 mm circle: it corrects field curvature across a full-frame sensor while reducing, which a simpler design would not manage at this speed.

On the FCT-65D specifically, this takes a 65 mm fluorite triplet from f/6.2 to f/5.2 while keeping full-frame coverage — a meaningful gain in exposure time on an already well-corrected tube.

Recommended Uses

Wide-field deep-sky imaging on the FCT-65D: large nebulae, extended objects, and framing that benefits from field rather than magnification.

Compatibility and Accessory Notes

Takahashi computes this version for the FCT-65D and FC-50. The threads are M55.9 (P=0.75) on the telescope side and M52 (P=0.75) on the camera side.

Note that the FCT-65D also has a dedicated 65D FU Reducer 0.65x, which is a different and stronger corrector. The 0.85x-M is the gentler option; the FU reducer takes the focal length down further. We stock both — tell us what you are framing and we will talk through which suits.

Good to Know Before You Order

The letter identifies the telescope, not the length: S, M and L all reduce by 0.85x. Ordering by telescope model is the way to get the right one.

Two reducers exist for the FCT-65D: this 0.85x and the dedicated 0.65x FU reducer. They give different focal lengths and suit different targets.

An imaging corrector: designed for a camera at the focal plane rather than an eyepiece.

Frequently Asked Questions

Is it difficult to set up?

No — it threads into the train on M55.9 at the telescope and M52 at the camera.

What will my FCT-65D become?

340 mm at f/5.2.

Will it cover a full-frame camera?

Yes — Ø44 mm image circle.

How is this different from the 65D FU Reducer?

The FU reducer is 0.65x and takes the focal length down considerably further. This one is the gentler 0.85x. Both are matched to the FCT-65D.

Bottom Line

The FCT-65D version of Takahashi's 0.85x Multi-Reducer — 340 mm at f/5.2 over a full-frame field.