An extension tube is very useful when the focal plane is far out. The focuser remains in the optimal position.
Areas of application:
- Straight-view observation with refractors (extension is necessary because the instruments are always designed for use with zenith prisms)
- Observation with Newtonian reflectors with long back focus (most Newtonians are already designed for photography, so an extension is often necessary for observation)
The extension tube is longer than the purely optical path, as the plug-in tube is not included in the measurement. It has a brass ring clamp that protects the eyepieces and a thread for attaching filters.
TS Optics is a brand of Teleskop-Service.
