Baader Telecentric System TZ-4 (4x focal length)

Telecentric with 2" outer diameter and with T2 thread on both sides
    Aplanatic, with 4x focal length extension and free of field curvature - delivers f/30 to telescopes with f/7.5
    Specially calculated and manufactured for the H-alpha wavelength, with the highest Strehl value (definition brightness at 656.3 nm)

 
Baader telecentric systems for focal length extension
To create a parallel beam path and sufficient back focus when used with SolarSpectrum H-alpha filters

Starting from an aperture ratio of f/15 (2x telecentric), f/10 (3x telecentric) or f/7.5 (4x telecentric), a parallel beam path with f/30 is created with the telescope aperture at full aperture using a TZS Opening ratio. With brighter telescopes, the aperture should be dimmed to such an extent that the end product results in 1/30 again. The distance to the camera sensor from the lens apex is 200mm for the TZ-2, 230mm for the TZ-4 and 250mm for the TZ-3. This leaves enough space behind the TZS for the H-alpha filter and any accessories, e.g. a 2″ diagonal mirror or any camera device imaginable. The optical calculation and the compensation are calculated for the H-alpha wavelength.

Please see the PDFs under the "Downloads" tab for further information
IMPORTANT NOTE

TZ systems are essential for the function of solar spectrum filters.

Please note that for H-alpha observation below 1 Ang full width at half maximum (FWHM) one absolutely needs a telecentric approach to achieve the recommended aperture ratio of f/30 to (preferably) f/40! Only with a telecentric approach can you create this perfectly parallel beam path, which is essential for the unrestricted function of such a complicated etalon.

This is a MANDATORY requirement. You could also set a telescope to an aperture ratio of f/30 optically - or using a Barlow lens - but that by no means means that this creates a parallel beam path. However, a slightly conical beam path with f/30 would only provide the contrast with an etalon with 0.5 Ang FWHM as if the filter had a pass width (FWHM) of 0.7 Ang or much worse.

It doesn't necessarily have to be a TZ-4. The new 2" Research Grade TZ-3 Telecentric System (3x focal length) (#2459257, € 445) is significantly better in terms of optics than the TZ-4, which is 20 years older. So it makes sense that you could go with one, for example TZ-3 RG starts and prefers to stop down the telescope aperture to f/30. This means that the contrast remains much better than with a poorly adapted system, where, for example, the older TZ-4 has a smaller free aperture than the Solar Spectrum-Etalon In the longer term, a newly calculated, large RG TZ-4 is in preparation - it is worth waiting for it and getting used to H-alpha observation later. TZ-3 and RG-TZ-4) and dim the telescope opening accordingly as required.

Only AFTER the H-alpha etalon can you expand the image field size using the new ResearchGrade Telecompressor 0.4

Basically - a Barlow lens has no place in an H-alpha system!

MANUFACTURER Baader Planetarium
ITEM NUMBER (#) 2459256
EAN CODE 4047825008695
NET WEIGHT (KG) 0.31
FOCAL LENGTH EXTENSION 4x
INTENDED USE Can be used for H-alpha observation with SolarSpectrum filters
INTERNAL CONNECTION (TELESCOPIC SIDE) thread, T-2 (M42 x 0.75)
EXTERNAL CONNECTION (TELESCOPIC SIDE) Socket, 2" (50.8mm)
EXTERNAL CONNECTION (EYECULAR/CAMERA SIDE) thread, T-2 (M42 x 0.75)