Telecentric systems are mainly used in H-alpha filters for solar observation, in which the 1/100 lambda plane-parallel Etalon in the H-alpha filter requires a perfectly parallelised beam path across the entire image.
This achromatic 3x telecentric lens is designed for the entire visible spectrum and can therefore not only be used with H-alpha filters, but also as an alternative to a Barlow lens.
Thanks to its parallel beam path, it is very forgiving in terms of working distance: While with a Barlow lens the magnification factor changes with the distance to the eyepiece or camera (zoom eyepieces are also based on this principle), the magnification factor and image quality of the TZ-3 do not change, even if the camera/eyepiece deviates significantly from the designed working distance (96 mm behind the thread base of the T-2 thread). The working distance can also be reduced, but then, especially with H-alpha approaches, you will not only observe the sun, but also structures within the etalon that are invisible at the correct working distance.
The achromatic TZ-3S illuminates an image field of 27.5 mm at a distance of 96 mm from the base, ideal for the small sensors of modern, fast planet cameras, which require high magnifications for photographing the moon and planets. The contrast is better than with simple Barlows or the eyepiece projection often used for high magnifications. With the 3x telecentric, the necessary high visual magnifications can also be achieved in combination with long-focus orthoscopic eyepieces. The eye relief of the eyepieces used also remains unchanged.
When using the 2" plug connection, the focus position is only shifted 3 mm outwards compared to a 2" eyepiece, so that the TZ-3S can also be used on binocular heads with a T2 connection instead of a 2.6x glass path corrector, e.g. to focus on planets with Newtonian telescopes.
The connection to the telescope is made via a dual 1.25"/2" plug-in sleeve with safety kerfs (these prevent tilting due to an incorrectly seated locking groove and also ensure a secure hold). On the camera side, the T2 thread provides a tilt-proof, secure connection even to heavy cameras or T2 eyepiece clamps. Extension rings for the T2 thread are available for almost all common connection systems (e.g. M48 / 2" / M68).
