Takahashi FC-35 0.66x Reducer for FC / FS Series

Product Overview

The FC-35 is Takahashi's 0.66x reducer for the FC and FS series refractors. On the FC-100DF it produces a 480 mm focal length at f/4.8, with a Ø44 mm image circle that covers a full-frame sensor. It was designed for digital imaging rather than adapted to it.

Each compatible telescope reaches a different focal length behind it, and each requires its own CA ring to set the correct backfocus. The CA ring is a separate purchase — see the table below for which one your telescope takes.

Who It's For

This is a good match if you image with an FC or FS series refractor and want a faster system with a flat field across a full-frame sensor.

Key Features & Design

• 0.66x reduction: the FC-100DF goes to 480 mm at f/4.8.
• Ø44 mm image circle: covers a 35 mm full-frame sensor, and it is the same figure on every compatible model.
• Six compatible telescopes: FC-100DF, FC-100, FS-102, FC-125, FS-128 and FS-152.
• Model-specific CA ring: sets backfocus for your particular telescope. Sold separately.

Optical / Mechanical Design

A reducer shortens the effective focal length and speeds up the focal ratio — the same target in less exposure time, over a wider field. What separates a good one from a poor one is what happens away from the optical axis: reduction tends to introduce field curvature and enlarge star images at the edges. The Ø44 mm image circle is the answer here, and it holds across all six compatible telescopes rather than shrinking on the longer ones.

The CA ring is what makes one reducer serve six telescopes. Each model presents its optics at a different distance from the focal plane, so the ring — in 100D, 102 or 130 form — sets the spacing correctly for that tube. Get the ring right and the reducer performs as specified; use the wrong one and the corner stars are where it shows.

Recommended Uses

Wide-field deep-sky astrophotography on an FC or FS refractor — large nebulae, extended galaxies, and mosaic panels where the extra field and the faster ratio both count.

Compatibility and Accessory Notes

We stock the Takahashi CA rings. Tell us which telescope and camera you are pairing this with and we will send the matching ring alongside it, so the train is complete when it arrives.

Good to Know Before You Order

The CA ring is a separate item: Takahashi supplies the reducer on its own, and the ring that sets backfocus for your telescope is bought with it. We will pair them for you — just tell us the model.

An imaging corrector, not a visual one: the FC-35 is designed for a camera at the focal plane and has no application in a visual train with an eyepiece.

The ring is telescope-specific: 100D for the FC-100DF, 102 for the FC-100 and FS-102, 130 for the FC-125, FS-128 and FS-152.

Frequently Asked Questions

Is it difficult to set up?

No — the CA ring does the work of setting the spacing for your telescope, so once you have the right ring it threads together directly. Getting the right ring is the step to take care over, and we will confirm it with you.

What does it do to my focal length?

Reduces it by roughly a third. On the FC-100DF that is 480 mm at f/4.8.

Will it cover a full-frame camera?

Yes — the Ø44 mm image circle covers a 35 mm full-frame sensor.

Is the CA ring included?

No. Takahashi sells the ring separately and it is specific to your telescope. We stock them and will pair the right one with your order.

Which telescopes does it fit?

The FC-100DF, FC-100, FS-102, FC-125, FS-128 and FS-152.

Bottom Line

A 0.66x reducer that turns an FC or FS refractor into a fast, flat, full-frame imaging system — 480 mm at f/4.8 on the FC-100DF, with the matching CA ring ordered alongside it.