Takahashi Collimating Eyepiece for Newtonians & Cassegrains

Product Overview

The Takahashi Collimating Eyepiece is a machined aluminum sighting tool that inserts into a standard 1.25″ (31.75 mm) eyepiece holder or focuser drawtube. Looking through the central peephole, you see the reflection of your primary mirror (on a Newtonian) or secondary/corrector assembly (on a Cassegrain or Ritchey-Chrétien) centered on the sighting hole when the optics are aligned. It has no lens elements — this is a mechanical collimation tool, not a viewing eyepiece. At 35 mm in diameter, 45 mm long and 45 g, it threads onto the Newtonian Collimating Tube with Crosshair for a combined Cheshire-eyepiece setup, or works on its own for a quick sighting check.

Who It's For

This is a good match if you own a Newtonian reflector and adjust your own mirror collimation, or if you run a Cassegrain or Ritchey-Chrétien telescope and check secondary mirror alignment between imaging sessions.

Key Features & Design

• Machined aluminum body: holds a consistent, repeatable fit in the focuser or eyepiece holder.
• Fixed 1.25″ barrel: drops straight into any standard visual back or drawtube, no adapter needed.
• Reflective sighting face: shows the primary mirror or secondary assembly reflected back through the peephole, centered when collimation is correct.
• Compact and pocketable: 35 mm diameter, 45 mm long, 45 g — easy to keep with your other collimation tools.

Optical / Mechanical Design

The tool is a simple sighting tube: a small peephole at the eye end and a reflective surface at the objective end, with an M36.4 x 1 male thread on the objective side. Used alone, it gives you a fast go/no-go check of primary mirror centering on a Newtonian. Threaded onto the Newtonian Collimating Tube with Crosshair, the two work together as a Cheshire eyepiece — the tube supplies a wire crosshair reference, and this eyepiece supplies the sighting hole, giving you a repeatable reference point for centering the secondary mirror shadow on Takahashi Epsilon astrographs and other Newtonian designs.

Recommended Uses

Pre-session collimation checks on Newtonian reflectors; secondary mirror centering on Cassegrain and Ritchey-Chrétien telescopes; a first-pass sighting reference before fine-tuning with a laser collimator or star test.

Compatibility and Accessory Notes

Fits any 1.25″ (31.75 mm) focuser drawtube or eyepiece holder. The M36.4 x 1 male thread on the objective end mates with the Newtonian Collimating Tube with Crosshair for combined Cheshire-eyepiece alignment on Newtonian and astrograph optical tubes.

Good to Know Before You Order

It has no lens elements. It is built for sighting down the optical axis, not for viewing the night sky — a standard eyepiece handles that job.

It does not include a crosshair. The crosshair reference for secondary mirror centering comes from the paired Newtonian Collimating Tube, which threads on separately.

Frequently Asked Questions

Is it difficult to set up?

No. It inserts into the focuser exactly like an eyepiece, with nothing to calibrate before use.

What is it best used for?

Checking whether a Newtonian primary mirror or a Cassegrain/RC secondary is centered on the optical axis.

Does it work for astrophotography setups?

It is a visual alignment tool used before imaging, not a component of the imaging train itself.

Do I need the collimating tube as well?

For a full Cheshire-eyepiece setup with a crosshair reference on a Newtonian, yes — the two are designed to thread together.

Bottom Line

A machined 1.25″ sighting tool for checking mirror alignment on Newtonian, Cassegrain and Ritchey-Chrétien telescopes, usable alone for a quick check or threaded to the collimating tube for a full Cheshire-eyepiece reference.