Baader SunDancer II Telecentric System TZ-3S

Baader SunDancer II 3x Telecentric TZ-3S

Telecentric systems are mainly used with H-alpha filters for solar observation, where the etalon in the H-alpha filter, which is plane-parallel to 1/100 lambda, requires a perfectly parallelized beam path over the entire image. These telecentrics provide very sharp images, but are mostly optimized for the H-alpha wavelength only.

This achromatic SunDancer 3x telecentric is calculated for the entire visible spectrum and can therefore not only be used on H-alpha systems, but also replace a Barlow lens. Due to the parallel beam path it is very good-natured regarding the working distance: While the magnification factor of a Barlow lens changes with the distance to eyepiece or camera (zoom eyepieces are also based on this principle), the magnification factor and imaging quality of the TZ-3 do not change, even if the new focal point deviates very significantly from the design working distance (65 mm).

The achromatic SunDancer II TZ-3S illuminates a field of view of 35 mm at 65 mm distance from the base body, ideal for the small sensors of modern, fast planetary cameras that require high magnifications for photographing the moon and planets. 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 together with long focal length orthoscopic eyepieces. Also the eyerelief of the used eyepieces does not change.

The telescope-side connection is made via a dual 1.25"/2" Barrel with Safety Kerfs (these prevent tilting due to an incorrectly seated safety groove and at the same time provide a secure hold). On the camera side, the T2 thread provides a tilt-proof, tight connection even to heavy cameras or to T2 eyepiece clamps. For the T2 thread, extension rings are available for almost all common connection systems (e.g. M48 / 2"/ M68).

Comparison of telecentric system versus Barlow lens
A telecentric system extends the focal length similar to a Barlow lens, but with a parallel beam path. This makes the working distance almost indifferent, and the quality and image scale remain the same. At the same time, the TZ-3S provides a high-contrast image. For the following comparison shot, a church steeple was photographed with an APS-C DSLR with the same camera settings; once with a Baader Q-Barlow, which was brought to a threefold magnification factor with extension rings (more about this can be found in this PDF), and once with the TZ-3S. On cameras with less than 35 mm image circle, edge shading is no longer a problem, and you benefit from higher contrast of the telecentric.