90 thread8" f/8 RC Astrograph - 203 mm aperture / 1624 mm focal lengthRitchey Crétien telescope for demanding astro imaging and observing.
Most large professional telescope are constructed according to the RC principle. Until recently, these telescopes were unaffordable for amateurs. RC telescopes from Teleskop Service are primarily aimed to amateur astronomers with photographic interest. These telescopes are perfectly suited for high-resolution astrophotography. Of course, an RC can also be used for visual observing. Here, the large corrected field of view is noticeable, too. In total, the stars are sharper than, for example, in a Schmidt-Cassegrain.
The advantages of the TS-Optics RC Telescopes at a glance
Astrophotography with the RC telescope
Hyperbolic primary and secondary mirror for a large fully illuminated field of view.
- Astrophotography with camera sensors up to 30 mm diameter possible without corrector. For larger sensors, like full-frame size, Teleskop-Service offers ready-to-use corrector solutions.
- 99% dielectric high-reflectivy coating on main and secondary mirror for an even brighter image.
- Significantly shorter cooling down time through open construction and active primary mirror ventilation.
- Internal baffles in the tube for even more contrast.
- High back focus for correctors, reducers and also binoviewers.
Due to the large corrected field of view, you can, for example, use a DSLR up to APS-C format without corrector. Thus the RC is a pure mirror system for astrophotography. The images become ultrasharp. For imaging dirctly in the focus, you will need the M90x1 extension tubes which are supplied. They are threaded between telescope and focuser, thus reducing back-focus.
The generous back-focus also allows attaching correctors which we recommend when using sensors of at least full-frame size. You can also attach a focal reducer, thus further increasing the speed of the RC.
You can connect the camera directly via 2" receptacle.
The advantages of a carbon tube over a metal tube
The weight reduction is minimal - only about 300 grams - the main advantage ist the focus stability when temperature changes. That is important for astrophotography. When temperatures drop, metal contracts and the focus moves. Refocusing is necessary. A carbon tube does not change, the combination of quartz glass mirror and carbon composite tube makes a readjustment of the sharpness obsolete, even for long time exposures.Choose your focuser
We recommend especially two focusers fitting directly to the M90 thread of the tube.MonorailM90
- the reasonably priced standard focuser. We recommend the focuser for visual observation and for lighter photo equipment, like e.g. DSLR cameras.
The focuser already provides all the prerequisites, such as micro-reduction and support superior to simple Crayford focusers. We recommend the focuser for accessories up to approx. 3 kg
V-Power focuser for heavy accessories We recommend the focuser to all astrophotographers who use heavier equipment.
The focuser carries accessories up to 6kg without tilting. Optional motor focus, 360 ° rotation and screw thread at the camera side are a matter of course.
Primary and secondary mirror of quartz glass
Quartz glass does not change its dimensions if temperature changes. When the temperature changes slowly during an exposure, other mirror substrates, like Pyrex, tend to a deformation of the mirror and thus to a shift of the focus. This problem does not exist for mirrors of quartz glass. Thus the focus is better maintained which is very important for long exposures. Both mirrors are coated with 99% reflectivity. The image is obviously brighter than the one of telescopes with only 90% or 94% reflection layer.
The advantages for astrophotography
The TS RC astrographa are true Ritchey-Chrétien telescopes. Maksutovs and Schmidt-Cassegrains have spherical mirrors and need correctors for making a large field usable. With Schmidt-Cassegrains, you can see the aberrations in the field even when working visually. Most times, Maksutov-Cassegrains are so slow that they are not suitable for astrophotography. RC telescopes have hyperbolical primary and secondary mirrors. They are more difficult to manufacture, but offer a significantly sharper field with less aberrations throughout the field.
Advantagesr to Schmidt-Cassegrain telescopes with correctors
Celestron EHD or Meade ACF telescopes need a corrector. Additionally, these telescopes have a Schmidt plate at the front side which is prone to dew. The RC is a pure reflection system without lenses in the light path. Thus you can use the complete light even in the infrared range. The image is brighter and the exposure times get shorter. The field of an RC telescope is coma-free by design and relatively flat.
No shifting problem
Telescopes with focusing via movable primary mirror often suffer from the "shifting problem". The image shifts while focusing or even jumps. By now, Meade and Celestron have the problem under control, but the effect is noticable nonetheless. TS RC telescopes do not have this problem, as their primary mirror is fixed. Focusing is done via a high-quality focuser. An additional advantage is the optimal distance from primary to secondary mirror. This gives you the guarantee of the best possible image. If the primary mirror moves relatively to the secondary, you will practically never have the optimal distance.
- 8" f/8 RC Astrograph (Carbon Fibre)
- 2x Dovetails - 1x Losmandy / 1x GP style
- M90 extension tubes for easy reaching of the focus
Powerful and lightweight 8" Ritchey Crétien with Quarz Optics and Carbon Fibre Tube.