Extender-Q 1.6x is a specific accessory suitable for the FSQ-106ED, whose role is not limited to a simple Barlow lens. Indeed, it makes it possible the refractor to keep optical properties closed to the traditional Takahashi refractors equipped with more general-purpose Fluorite doublet or ED triplet : more focal length, reduction of the under-correction for astrophotography and visual contrast enhancement. The accessory is screwed at the refractor prime focus and it is delivered with several extension tubes.