40mm dovetail extension tube for refractor Crayford focusers

40mm extension tube for many 2" Crayford focusers for refractors

The extension is placed between the focuser and its base in order to avoid vignetting and for maximum stability.

40mm extension for refractor focuser

Refractors with 2" focusers are typically designed for use with 2" star diagonals. For astro imaging, where no diagonal is used, this can mean that you won´t reach focus because you will hit the limit of the focuser´s outward travel. Normally you will need to use a 2" extension tube to fix the problem.

Problems with 2" extension tubes or with focusers in their most outward position

Mechanical stability suffers when using a 2" extension or when moving the focuser to its most outward position. The camera might be tilted slightly out of alignment, resulting in lower image quality.

Some vignetting might occur because of the long length of the focuser drawtube and extension tube combined. The fully illuminated field gets smaller.

The TS 40mm dovetail extension tube is the solution

The TS extension tube is not placed in the 2" clamp of the focuser, but instead it is placed between the focuser´s body and its base. The extension fits for many focusers available today.

Mechanical stability is much better than a classic 2" extension. Overall stability gets even better by the fact that the focuser´s drawtube does not need to be extended as much.

The fully illuminated field is larger because of the shorter length of the 2" barrel.

The extension adapts to, among others:

TSFOCR2M

MonorailR2

Baader Steeltrack 2" Refractor version