Baader TZ-3S telecentric system for SunDancer II

Baader TZ-3S telecentric system for SunDancer II

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

This SunDancer 3x achromatic telecentric is designed for the entire visible spectrum and can therefore not only be used in H-alpha systems, but can also replace a Barlow lens. Due to the parallel beam, it is very good with respect to the working distance: While the magnification factor of a Barlow lens 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 does not change, even though the new focal point deviates very significantly from the working distance of the optical design (96 mm).

The achromatic SunDancer II TZ-3S illuminates a 35 mm image circle at a distance of 96 mm from the base body, ideal for the small sensors of modern, fast planetary cameras that require high magnification to photograph the moon and planets. Contrast is better than with simple barlows or ocular projection typically used for high magnification. With the 3x telecentric system, the high magnifications needed for visual observations can also be achieved with long focal length orthoscopic eyepieces. The interpupillary distance of the eyepieces used does not change either.

The connection on the telescope side is made via a 1.25"/2" double nosepiece with safety slots (these prevent tilting due to an incorrectly positioned safety slot and, at the same time, provide a secure hold). On the camera side, the T-2 thread provides a fixed, tilt-proof connection even with heavy cameras or T-2 eyepiece clips. Adapter rings for almost all common connection systems (e.g. M48 / 2"/ M68) are available for the T-2 thread.

Comparison of telecentric systems with Barlow lenses
A telecentric system extends the focal length similar to a Barlow lens, but with parallel light beams. This means that the working distance is almost the same, and the image quality and scale remain the same. At the same time, the TZ-3S offers 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 triple magnification factor with spacer sleeves (more on this can be found in this PDF), and once with the TZ-3S. For cameras with an image circle smaller than 35 mm, edge shading is no longer an issue and benefits from the higher contrast of the telecentric.

Comparison of Baader SunDancer II H-alpha Filter and Baader SunDancer II TZ-3S

The telecentric system of the Baader SunDancer II H-alpha Filter (#1363056) is the same as the Baader SunDancer II 3x telecentric TZ-3S, but additionally contains a 2nm blocking filter (FWHM). This filter glows gold when looking at the SunDancer from the side of the telescope. This blocking filter is absolutely necessary to protect the actual H-alpha filter from solar radiation. The 3x telecentric system is available as Baader SunDancer II 3x Telecentric TZ-3S without a blocking filter, e.g. for use with other H-alpha filters. The blocking filter, however, is not available separately.

The blocking filter reflects the sunlight just before the etalon and the telecentric system. This protects the etalon from excessive heat. In addition, an etalon also transmits wavelengths that are a multiple of the desired transmission line; these are also blocked by the blocking filter.

Technical specifications:

• MANUFACTURER Baader Planetarium
• SKU (#) 1363070
• EAN CODE 4047825042903
• FOCAL EXTENSION 3x
• USAGE for H-alpha observation with SolarSpectrum filters
• EXTERNAL CONNECTION (LENS SIDE) Barrel, 1¼", 2" (50.8mm)
• EXTERNAL CONNECTION (EYE/CAMERA SIDE) Thread, T-2 (M42 x 0.75), 1.4" (35mm)

Baader TZ-3S Telecentric System for SunDancer II