Takahashi FCT-L CO 114D Adapter for Reducer and Corrector

The Takahashi FCT-L CO 114D ring is the connection adapter designed for use with the FCT-L 0.8x reducer or the FCT-L 0.99x field corrector in conjunction with the FCT-114DF, FCT-114DS, and FC-100DZ telescopes. It is part of the photographic setup defined by Takahashi and ensures the proper optical path for these instruments. The choice of adapter depends on the telescope used, even when the accessories share the same thread diameter.

The CO ring on the FCT-114D and FC-100DZ

The optical path length of the CO 114D is 20 mm. Takahashi notes that the two rings in the FCT-L CO series have different lengths to provide the appropriate spacing and correction for each optical system. The CO 114D should therefore be used with both versions of the FCT-114D as well as the FC-100DZ. The FC-100DF, on the other hand, uses the CO 100DF ring.

Both sides of the ring feature an M72 female thread with a 1 mm pitch. In the assembly diagrams, it is positioned between the FCT-L reducer or corrector and the camera connection adapter. The FCT-L converters have an M72 male thread on each side; the CO ring thus serves as the connecting element in this part of the camera assembly.

Two Documented Photographic Journeys

With a CMOS camera, the assembly continues with the M72-to-M48 or M72-to-M54 adapter, selected based on the camera’s thread. The specified distance is 55 mm between the base of the camera-side thread on this adapter and the sensor plane. This measurement therefore has its own reference point; the 20 mm optical path of the CO ring does not replace this mounting specification.

For a Canon EF or Nikon F camera body, the diagrams call for the M72 WR adapter and the corresponding DX-WR wide-field ring. The CO 114D ring remains in place in the assembly with these cameras. The M camera rotator is also used on the eyepiece side. The diagram for the FCT-L field corrector additionally shows the M72 L52 extension tube; be sure to check which parts are already installed on the instrument.

The CO 114D measures 76 mm in diameter and 20 mm in length, and weighs 32 g. It is sold separately from the FCT-L converters. To assemble the system, you must distinguish between this ring, which is designed for the telescope, and the adapter designed for the camera. Referring to the diagram corresponding to the reducer or corrector ensures that you follow the specified connection order and use the appropriate ring for each instrument.

Technical specifications

Compatible glasses in the catalog

• Takahashi FCT-114DS – 114 mm fluorite telescope, tube only
• Takahashi FCT-114DF – 114 mm fluorite telescope, tube only
• Takahashi FC-100DZ – 100 mm fluorite telescope with finder scope and mount
• Takahashi FC-100DZ – 100 mm fluorite telescope, tube only

Technical Documentation

• Takahashi Installation Diagram for the FCT-L Gearhead (PDF)
• Takahashi Installation Diagram for the FCT-L Corrector (PDF)
• Takahashi Technical Presentation on the FCT-L Reducer and Corrector (PDF)

Takahashi's Official Presentation of FCT-L Accessories

Selecting the elements for the montage

• FCT-L 0.8x Focal Length Reducer, sold separately.
• FCT-L 0.99x Field Corrector, sold separately.
• M72 Male to M48 Male Adapter for M48 CMOS Camera, sold separately.