Takahashi Collimating Telescope for Refractors, Cassegrains & Ritchey-Chretiens

Product Overview

The Takahashi Collimating Telescope is a 6x18mm sighting scope built for aligning refractor, Ritchey-Chrétien and classical Cassegrain optics, including Takahashi's own Mewlon-250CRS, Mewlon-300CRS and CCA-250. It threads directly into the focuser on an M36.4 x 1 male thread and uses a 45-degree angled eyepiece for a comfortable viewing position while sighting down the optical axis. At 210 mm long, 40 mm in diameter and 235 g, it comes with a four-page instruction manual.

Who It's For

This is a good match if you own a Takahashi Mewlon Dall-Kirkham telescope, a CCA-250, or a refractor with a focal length of 820 mm or longer, and you check collimation as part of your setup routine.

Key Features & Design

• 6x18mm sighting optics: a magnified, focused view down the optical axis for precise alignment.
• 45-degree angled eyepiece: keeps the viewing position comfortable regardless of where the focuser points.
• M36.4 x 1 male thread: threads directly into the focuser drawtube, the same interface as the Collimating Eyepiece and Collimating Tube.
• Manual focus: extend or retract the eyepiece to bring the sighting image into focus.

Optical / Mechanical Design

Unlike the Collimating Eyepiece, this is a true 6x18mm achromatic sighting telescope rather than a bare peephole. You focus it by extending and retracting the eyepiece tube by hand, and the 45-degree mirror redirects the view for a comfortable angle regardless of where the telescope is pointed. The magnified image makes fine centering errors easier to see than a direct sighting tool would.

Recommended Uses

Collimating Mewlon-180C, Mewlon-210, Mewlon-250CRS and Mewlon-300CRS Dall-Kirkham telescopes; centering the secondary mirror on the CCA-250; checking objective alignment on refractors of 820 mm focal length or longer.

Compatibility and Accessory Notes

Threads via M36.4 x 1 male into any focuser accepting that thread, matching the interface used by Takahashi's Collimating Eyepiece and Collimating Tube. Also compatible with GSO, PlaneWave and RCOS Cassegrain and Ritchey-Chrétien tubes that have a marked secondary mirror for collimation reference.

Good to Know Before You Order

It isn't built for relay-lens Cassegrains. Takahashi doesn't recommend it on Cassegrain designs that use a relay lens as part of the optical path.

Third-party RCs need a marked secondary to use it. On GSO, PlaneWave and RCOS tubes that means a secondary mirror with a collimation mark; if you're not sure your tube has one, send us the model and we'll help you check.

Frequently Asked Questions

Is it difficult to set up?

No — it threads into the focuser exactly like an eyepiece, and focus is a simple extend-and-retract adjustment.

What is it best used for?

Aligning the optical axis on Takahashi Mewlon Dall-Kirkham telescopes, the CCA-250, and refractors of 820 mm focal length or longer.

Does it work on Cassegrains generally?

On classical Cassegrain and Ritchey-Chrétien designs with a marked secondary, yes; not on designs that use a relay lens.

What comes in the box?

The collimating telescope and a four-page instruction manual.

Bottom Line

A 6x18mm sighting scope for aligning Takahashi Mewlon, CCA-250 and long-focal-length refractor optics, threading directly into the focuser and focusing by hand.