TZ-3 Telecentric System 2" – Research Grade (3x focal length)

This is a little bit complicated way of explaining how to find the perfect distance between TZ and camera/eyepiece, if the optical length of the H-alpha-filter is unknown. If you put a paper screen at the working distance of the TZ behind the extension tube (the "poster tubes"), it acts as a projection screen. This way, you can safely point the telescope at the sun and see where the image is sharp. The ERF doesn't block enough sunlight to do this with an eyepiece or camera, that's why the paper as screen is used. When you see the image of the sun, then you focus as usual with the telescope's focuser - of course, this has to be done with every telescope, and also, when you have used the telescope at night or with a Herschel wegde at day. This method makes sure that you get the perfect position for the TZ in relation to the telescope and can later place camera/eyepiece in the perfect distance to the telecentric system. If you then remove the poster tube and add the H-alpha-filter directly behind the TZ and focus it by moving the eyepiece (which is basically looking at the sharp image "floating" in the air, where the paper was), then all the distances are perfect. If you remember the setup (TZ, H-alpha-filter, star diagonal, eyepiece clamp, extension tubes if necessary), you only need to do this once. Then you can take the whole setup and put it into your telescope (or any other telescope) and simply focus it with the telescope's focuser - just like with every camera/eypiece. This whole procedure is simply to bring eyepiece/camera into the perfect working distand behind the TZ, when the optical length of the H-alpha-filter is unknown. Fortunately, in real life, these distance doesn't have to be exact. Usually, you get pretty good results if you simply place the eyepiece in a star diagonal, so that the complete setup of H-alpha-filter (which is now connected directly to the TZ), star diagonal (BBHS-prism is recommended) eyepiece clamp and field stop of the eyepiece (which is located at the distance from the TZ where the paper screen was) is as long as the working distance of the TZ (250mm for the research grade TZ3). Usually, there isn't much change in image quality even if you are some 5 cm closer or farther away due to the parallel beam of light behind the TZ, and you can simply focus the whole system with your telescope's focuser. But for best results, you can determine the perfect distance between the back of the TZ and the eyepiece or camera with the method mentioned above. It safes you the problem that the optical length of the H-alpha-filter is usually not known exactly.

Unfortunately you will not reach focus if the backfocus distance is too short and the focal point will not be in the right place

The main difference between TZ-3 and the older constructions TZ-2 and TZ-4 is that TZ-3 has 46mm clear aperture at the H-alpha-filter entrance side. This is suitable for research grade SolarSpectrum H-alpha filters. Another difference is the longer working distance of 250mm for optimized focal length reduction with a telecompressor and suitable room for adapting a binocular viewer. Optically the image quality is as good as you know it from your TZ-2.

Its very easy: There is the name of the item written on it. When you are behind the telescope, were the camera/eyepiece is, you must be able to read the text (text is not upside down) Means the big lens points to the filter/camera/eyepiece, the smaller one to the telescope

1. The TZ-3 is a new design with larger lenses to fully cover the 46 mm aperture of the Solar Spectrum Research grade H-alpha Filters. It is not only designed for H-alpha but for CaK as well. 2. No it is a more elaborate optical design to cover both wavelengths 3. Yes - if you only intend to use it on H-alpha and if the entrance window of your H-alpha filter is not larger than 36 mm 4. No - the TZ-3 has another shape owing to it´s larger lenses. Also it does feature 2" SC-threads as well as reducers for T-2 (M42x0,75 mm). Only the TZ-3 can be mounted straight onto the back end of Celestron Schmidt-Cassegrain telescopes to - also - work with our new generation of Triband-SCTs: https://www.baader-planetarium.com/en/telescopes/baader-planetarium/triband-sct-schmidt-cassegrain-based-multi-purpose-telescope-for-sun-and-deep-sky.html

This definitely is not the case. Neither the TZ-3 nor any other TZ-system can retain its designed optical performance, when the distance between the internal lens groups is being altered. Answers for individual questions: 1) The middle intersection roughly marks the position of the initial instrument focal length. The middle section cannot be removed. 2) The middle intersection bears a mask (straylight shield). No part of this product is being "reused" on any other product. 3) A large deviation from the designed 250 mm focal lenght is not advisable. Noticeable deterioration of the image contrast would be inevitable.