Baader T-2 extension tubes enable you to securely add space between T-2 components. This T-2 #25B 1508153 T-thread extension (spacer tube) provides 40mm of extension. It features an internal T-2 thread (M42x0.75) at one end and an external T-2 thread at the opposite end. Full internal threading and blackening kills any stray light reflections.
40mm optical path length
Telescope side T-2 internal thread
Focus side T-2 external thread
For eyepiece projection with shift/sliding focuser
For over 30 years Baader have focused on the Astro T-2 thread system (M 42 x 0.75 mm); virtually every telescope manufacturer must offer this thread far ahead of the focal point of his instrument, such a universal T-ring (for DSLR cameras) can be connected.
The only exceptions are (still) Russian equipment, there the thread diameter is the same, but the pitch is still 1mm per revolution - rather than 0.75mm! Therefore, Baader offers among other things a "Russians adapter". At only 7mm additional optical length it can allow so many Russian lenses or telescopes to be compatible with an international Astro T-2 (M 42 x 0.75mm) connector!
For the sake of better recognition mostly are marked. See marking small 'a' or small 'i' in the respective indication! "a"; identifies an external thread (male); or, if Ø sign which a diameter, "i"; - a female is always (female) or - Ø character - an inner diameter.