Baader Planetarium TZ-3S Telecentric System T-2 for SunDancer II and more

The 3x Telecentric Advantage: Parallel Light and Stable Magnification

Unlike a Barlow lens, which creates a diverging light cone and whose magnification changes with distance, a telecentric system produces parallel light rays. This core design principle ensures the magnification factor of the TZ-3S remains a constant 3x, regardless of where your camera or eyepiece is placed relative to its 96 mm optimal working distance. The result is a stable image scale and superior image quality, free from the optical compromises inherent in extending a Barlow's magnification with extension tubes.

Achieving the Mandatory f/30 for H-alpha Etalons

For sub-Angstrom H-alpha filters like the Baader SunDancer II, a telecentric system is not an optional accessory—it is an essential prerequisite. These filters rely on an internal etalon that only performs to specification when fed a perfectly parallel beam of light at f/30 or slower. Simply using a Barlow to increase a telescope's focal ratio to f/30 does not create a parallel beam and will severely degrade the filter's contrast. The TZ-3S correctly converts a standard f/10 telescope into an f/30 instrument, ensuring the etalon performs at its maximum theoretical contrast.

Achromatic Imaging: Illuminating a 27.5mm Image Circle

While designed for H-alpha, the TZ-3S is a fully achromatic system, corrected across the visible spectrum. This makes it a powerful tool for high-magnification lunar and planetary imaging, delivering higher contrast than simple Barlows or eyepiece projection. The system illuminates a 27.5mm image circle, making it an ideal match for the smaller sensors found in modern, high-speed planetary cameras that thrive at the high magnifications needed to resolve fine detail on Jupiter's cloud bands or the Cassini Division in Saturn's rings.

Mechanical Interface: Dual 1.25"/2" Nosepiece and T-2 Threading

The TZ-3S is built for secure, flex-free integration into any imaging train. On the telescope side, a dual-purpose nosepiece fits both 1.25" and 2" focusers and features safety kerfs instead of a simple groove, preventing tilts and ensuring a solid lock. On the camera side, a standard T-2 (M42x0.75) male thread provides a rigid, direct connection to cameras, filter wheels, and T-2 eyepiece holders, eliminating the potential for sag that can occur with simple thumbscrew connections.

TZ-3S vs. TZ-4S: Matching f/10 vs. f/7.5 Telescopes

Choosing the correct telecentric depends on your telescope's native focal ratio. While the TZ-4S offers a larger 36mm clear aperture, its primary purpose is different.

• TZ-3S (Gold Label): This 3x telecentric is optimized for telescopes with a focal ratio of f/10, converting them to the target f/30 for H-alpha filters.
• TZ-4S (Violet Label): The 4x telecentric is designed for faster telescopes around f/7.5, providing the necessary magnification to reach the same f/30 target.

This standalone TZ-3S does not include the 2nm blocking filter required for the SunDancer II system; that component is only integrated into the red-ring version sold with the filter itself.