Takahashi SD Tube for FS‑60C Flattener (TKA20583)

Takahashi SD Tube for FS‑60C Flattener (TKA20583)

This SD (short-distance) extension tube is engineered to fine-tune the back-focus when using the dedicated FS‑60C flattener. With approximately 6 mm of added optical length, the TKA20583 allows true prime-focus sharpness from close-in terrestrial imaging to the night sky, maintaining exact parfocality across the full field.

Machined from black-anodized aluminum with precise internal threading, it aligns the flattener and camera train without inducing tilt or misalignment. It’s the essential missing link when pairing the FS‑60C flattener to a DSLR or modern color CMOS camera on the compact FS‑60C or FS‑60CB refractor.

Cloudy Nights Community Insight

Among users discussing the FS‑60 series imaging train, many emphasize the importance of the SD tube’s exact length. One observer noted that it is “essential for getting the flattener to focus to infinity” and “ensures flat stars across the corner, even on APS‑C sensors.” This consensus underscores its role in achieving crisp, well-corrected wide-field images.

Observing Tip

Install the SD tube between the flattener and camera adapter—ideally before adding the camera—to ensure that all components align snugly without having to adjust focuser drawtube each time. It’s a small part that saves big headaches: consistent focus, best corner stars, and avoidance of flange lock-ups during intense imaging sessions.