Takahashi FOA-60 Extender 1.7XR

Product Overview

The FOA-60 Extender 1.7XR converts Takahashi's FOA-60 Ortho Apochromat to the same 900mm f/15.0 configuration published for the dedicated FOA-60Q optical tube, with the image circle opening to 88mm and back focus extending to 208.1mm. It is built into the optical path the same way the FOA-60Q's factory objective is, rather than mounting on the drawtube as a Barlow would.

Who It's For

This is a good match if you already own the FOA-60 and want the FOA-60Q's long-focal-length performance — high-resolution lunar and planetary imaging and high-power visual observing — without buying a second optical tube.

Key Features & Design

• Converts FOA-60 to FOA-60Q spec: 530mm f/8.8 becomes 900mm f/15.0, matching Takahashi's own FOA-60Q tube exactly.
• 88mm image circle at the extended focal length, with 208.1mm back focus.
• Preserves the FOA-60's correction: Takahashi states the resulting system holds a Strehl ratio above 99% across nearly the full visible spectrum.
• Supports high magnification: Takahashi rates it for visual magnifications up to 300x while keeping the image clean.

Optical / Mechanical Design

The FOA-60's 60mm fluorite doublet objective is built for correction quality over field width; the 1.7XR extender lengthens the light path to 900mm at f/15.0 — identical to the factory FOA-60Q configuration — while the doublet's inherent correction keeps the Strehl ratio high through the extended path. This is the same route Takahashi uses to build the FOA-60Q itself, applied to an FOA-60 already in the field.

Recommended Uses

High-resolution lunar and planetary imaging, and high-magnification visual observing of the Moon, planets, and double stars, on an FOA-60.

Compatibility and Accessory Notes

Takahashi publishes this pairing for the FOA-60 specifically.

The resulting figures match Takahashi's own FOA-60Q optical tube exactly. It is not combined with the FOA-60 0.93x Flattener, which serves the opposite, wide-field configuration of the same tube. See the Takahashi Back Focus Guide for general spacing reference.

Good to Know Before You Order

Not combined with the 0.93x Flattener: the two accessories serve opposite configurations of the FOA-60 and are not used together.

Frequently Asked Questions

Is it difficult to set up?

No — it installs into the optical path the same way the FOA-60Q's factory objective assembly does, with the resulting 208.1mm back focus fixed by the conversion.

What is it best used for?

High-resolution lunar and planetary imaging and high-power visual observing.

Does this make my FOA-60 an FOA-60Q?

Optically, yes — the resulting focal length, ratio, image circle, and back focus match Takahashi's FOA-60Q tube exactly.

Can I still use the FOA-60 at its native focal length afterward?

The extender is a conversion rather than a drop-in accessory; if you want to switch back and forth between native and extended configurations, send us your setup and we will confirm what that involves.

Bottom Line

The FOA-60 Extender 1.7XR turns an FOA-60 into the optical equivalent of Takahashi's FOA-60Q — 900mm at f/15.0 with an 88mm image circle and 208.1mm of back focus, for high-resolution lunar and planetary work.