121 mm Extension Tube for 3" FT Focuser (STE-M109-121)

Name: 121 mm Extension Tube for 3" FT Focuser (STE-M109-121)
Brand: Stellarvue
SKU: STE-M109-121
Price: 96.75 USD
Availability: InStock
Rating: 5.0 (5 reviews)

121 mm Extension Tube for 3" FT Focuser (STE-M109-121) - Main image

$96.75 ~~$129~~ In stock

Category: Astrophotography Accessories

Description

The Stellarvue STE-M109-121 is a 121 mm threaded extension for the 3" Feather Touch Focuser. The focuser and rotator thread into this to provide 121 mm of additional distance between the objective and the focuser. Threads are M109X1.

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Customer Reviews (5.0 / 5 · 5 reviews)

Sofia ★★★★★ Oct 21, 2026

The threads on this extension are incredibly smooth—it screwed right onto my 3" focuser without any binding. It’s exactly the 121mm I needed to fix my back focus issues for my imaging setup.

John ★★★★★ Oct 20, 2026

This 121mm extension gave my imaging train exactly the spacing it needed without any wobble. The threads are smooth and precise, making it straightforward to attach to the focuser. It’s a solid, well-made piece that solved my back focus issues instantly.

Grace ★★★★★ Oct 19, 2026

The threads on this extension tube are buttery smooth and mated perfectly with my 3" focuser, giving me the exact 121mm of back focus I needed for my imaging train. No wobble or play at all once tightened down.