TS-Optics 15 mm Extension Adapter for M90x1 thread

TS-Optics M90 Extension Tube for the M90x1 thread - length 15 mm

Many telescopes, for example Ritchey-Chrétien telescopes, have much backfocus. This generous distance of the focus allows using a focal reducer or accessories like off-axis guiders. But if you want to attach only a camera or possibly just to do direct-vision observations, than the focuser has to be completely extended and additional 2" extension tubes have to be used. That reduces stability.

This M90 extension solves the problem. It is threaded between focuser and telescope and increases the distance betweeen telescope and focuser - see image at left.

The focal plane or focal point moves closer to the focuser and you don´t need to extend the drawtube that much. For attaining precise matching, you can also thread several M90 extension tubes together. A further advantage is the better illumination. The clear aperture of the extension tube is clearly larger than the clear aperture of a 2" extension tube.

The external thread is 5 mm long. This is sufficient for all focusers and adapters that are screwed directly onto the extension. The thread is too short for focusers with a counter ring.

Safety informations: PDF Download