Triband SCT – Multi-purpose telescopes for professional applications
The Triband-SCs with Triband-ERF-coated Schmidt-corrector were designed on the base of the time-tested Celestron Schmidt-Cassegrain (SC) telescopes. They are the ideal basis for detailed views of the Sun in H-alpha with a large aperture. These telescopes also remain nice instruments for Deep-Sky observations.
Size matters - even for solar observation!
It is a common misconception that small telescopes are sufficient for observing the Sun as high magnifications can rarely be used at daytime. The nice little H-alpha and CaK telescopes which are quite common nowadays are great for a quick look at the Sun and to see the complete solar disk – but if you want to see fine details, you need aperture and focal length to make use of those moments when the seeing is perfect.
The groundbreaking Baader Triband-SCTs have got an Energy Rejection Filter (ERF) – which is necessary for the SolarSpectrum CaK and H-alpha filters – already integrated into the Schmidt corrector plate. You don't have to pay the additional costs for an Energy Rejection Filter (ERF), which would be "astronomical" for telescopes between 8 and 11 inches. With its Triband-coating, the telescope is still perfectly fitted for narrowband Deep-Sky-photography, although it was made for solar observing!
Triband-coating is an Energy Rejection Filter for observing the Sun, which does not interfere with narrowband Deep-Sky observations. Heat shields avoid heating of the telescope.
The special Triband-ERF Schmidt corrector plate of the Triband-SCT has got transmission windows in the following parts of the spectrum: 380 to 400 nm, 480 to 515nm and 630 to 680 nm. In addition, it is blocked in the UV range (below 380nm) and in the IR range (above 680nm) in order to prevent both – short-wave radiation and heat development.
The groundbreaking Baader Triband-SCTs have got the energy rejection filter (ERF) – which is necessary for the SolarSpectrum CaK and H-alpha filters – already integrated into the Schmidt corrector plate. Especially in IR, the Triband Schmidt corrector is blocked down to 1450nm, so that the telescope will not heat up. So, you do not need an additional large and precisely polished ERF, and you can use the full optical quality of the Schmidt corrector. Additional rear-ventilated heat shields in front of tube and secondary mirror also keep the tube from heating up by the Sun's radiation. This way, you can use the full resolution which is available at your location. With videography it is possible to achieve extremely high-resolution detail images of the Sun. And you can do this at three wavelengths – not only in H-alpha! You can observe the Sun in H-alpha as well as in CaK with a Baader Planetarium and SolarSpectrum filter, or in in continuum (white light) with a Herschel wedge or an ASTF filter. The system is also great for visual observations – the sun will impress you more than ever in those moments when the seeing is good.
TriBand-frontfilter for narrowband observations
With a Triband-SCT, you get a Schmidt-Cassegrain optical tube assembly with a Triband-ERF-coated Schmidt corrector plate and rear ventilated heat shields for tube and secondary mirror (with Neodymium-magnetic holders). The transmission windows are designed for Calcium-K, Continuum (incl H-beta and O III), H-alpha, S II and let you use additional narrowband filters.
For the following uses, you need further equipment:
- H-alpha: Solar Spectrum H-alpha filter, TZ-3 telecentric system and telecompressor TK0.4 or TK0.7. An additional D-ERF filter is not required.
- CaK: Solar Spectrum CaK-filter, Calcium CaK filter plus additional frontfilter for observing the Sun in CaK
- White light: Safety Cool-Ceramic Herschel prism plus optional narrowband filters
- Deep-Sky (not for solar observations!): Deep-sky filters according to your field of interest (RGB / H-beta / O-III / H-alpha / S-II)
SolarSpectrum-Filter for H-alpha or CaK can be connected directly
Observing the Sun in H-alpha
The Triband-SC were developed for the SolarSpectrum H-alpha filters. The Energy Rejection Filter which is integrated into the Schmidt corrector plate eliminates the need for an additional D-ERF. The SolarSpectrum filters require the TZ-3 Telecentric System 2" – Research Grade (3x focal length) (#2459257 , € 445,- ) , to perform at its best at f/30; with the Telecompressor 2" H-alpha 0.4x – Research Grade, for Solar Spectrum (#2459260 , € 366,- ) with 16mm corrected field of view, you almost regain the original focal length of the telescope and can work both visually and photographically at lower magnifications.
Observing the Sun in CaK
In addition to the transmission window between 630 and 680 nm for H-alpha observation, the Energy Rejection Filter has a second window between 380 and 400 nm, in the dark blue/UV. It is made for using SolarSpectrum CaK filters without an additional Energy Rejection Filter.
In addition, the filter can be used, but only behind another filter such as a Cool-Ceramic Safety Herschel Prism 2" Mark II – Photographic (#2956510P , € 645,- ) or AstroSolar photo film ND 3.8 (also available as BDSF: OD 3.8 Baader Digital Solar Filter 200mm (#2459376 , € 157.91 ) in matching mount).
Observing the Sun in continuum (white light)
Solar observation in white light can be done with a Cool-Ceramic Safety Herschel Prism 2" Mark II – Photographic (#2956510P , € 645,- ) or a temperature-compensating ASTF front filter made of astrosolar film.
Depending on each model these are:
- 8" SCT = ASTF 200 – AstroSolar Telescope Filter OD 5.0 (#2459316 , € 176,- )
- 9.25" SCT = ASTF 240 – AstroSolar Telescope Filter OD 5.0 (#2459317 , € 201,- )
- 11" SCT = ASTF 280 – AstroSolar Telescope Filter OD 5.0 (#2459318 , € 215,- )
The Sun appears slightly light green. For increased contrast, we recommend a red filter like H-alpha 2" Bandpass filter (20nm) (#2961853 , € 165,- ) to reduce the influence of seeing, or the O-III 2" Super-G Filter (9nm) - CMOS optimiert (#2961551 , € 165,- ) .
A note about solar observing
Please note that a Triband SCT is no grab-and-go-telescope: Smaller telescope with less magnification will show nice images even at poorer seeing conditions, but a high-end telescope which pushes everything to its limits also requires a proper location. Make sure that your surroundings don't cause bad local seeing – only then you can take the telescope to its limits!
Use a Herschel Wedge or an ASTF front filter to see the sun in white light with large apertures and high resolution.
Deep-Sky narrowband observation and narrowband photography
The Triband-SCTs are based on Celestron's Schmidt-Cassegrains, a well-tried and reliable no-frills telescope system. That's why they are also compatible with a multitude of accessories which were developed for regular Schmidt-Cassegrains – starting with filter drawers like the UFC or focusers like the Baader Diamond SteelTrack with optional motor focuser or the Celestron Fokussiermotor #821160 up to reducers. In contrast to pure H-alpha telescopes, the triband SCT can also be used at night: The filter coating allows CaK, H-Beta, O-III, H-alpha and S-II to pass through. The telescopes therefore harmonize very well with UHC-L, O-III and H-Beta filters - that is all filters used for visual observations. At night, you only need to replace the H-alpha filter or Herschel wedge by a normal prism and eyepieces. Narrow-band photography is also possible. However, the Celestron EdgeHD and RASA telescopes with their reducers/field flatteners designed for modern cameras are better suited for Deep-Sky photography.
Triband-SCT - Schmidt-Cassegrain-based Multi-Purpose-Telescope for Sun in H-alpha, CaK and Continuum
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