TS-Optics 203 mm f/12 classical Cassegrain This 203 mm classical Cassegrain combines a parabolic primary and hyperbolic secondary to give a 2436 mm focal length at f/12. The all-reflective optical train is suited to high-magnification observing and lunar/planetary imaging.
Manufacturer model: TS-Optics 203 mm f/12 classical Cassegrain · Specifications checked against manufacturer data on 2026-11-04
This 203 mm classical Cassegrain combines a parabolic primary and hyperbolic secondary to give a 2436 mm focal length at f/12. The all-reflective optical train is suited to high-magnification observing and lunar/planetary imaging.
A separate 2-inch dual-speed Crayford focuser adjusts the camera or eyepiece. The manufacturer specifies roughly 150 mm backfocus from the 2-inch socket and an M90 × 1 focuser connection on the tube.
The 203 mm version’s table provides its own reflectivity, secondary obstruction, tube dimensions, mass and dovetail arrangement. These values are not borrowed from the other aperture. Suitable adapters and optical extensions depend on the eyepiece or camera train.
TS-Optics manufacturer documentation
Classical Cassegrain, not Ritchey–Chrétien or Schmidt-Cassegrain. Manufacturer’s aperture-specific reflectivity and linear-obstruction values retained.
| F ratio | f/12 |
|---|---|
| Colimation aid | central marks on the secondary mirror for easier collimation |
| Suitable for infrared photography | yes |
| Backfokus | roughly 150 mm from the 2" receptacle |
| Secondary mirror obstruction | 33% (linear) |
| Connection thread of the focuser | M90x1 on the tube |
Data sheet
Specific References
TS-Optics 203 mm f/12 classical Cassegrain This 203 mm classical Cassegrain combines a parabolic primary and hyperbolic secondary to give a 2436 mm focal length at f/12. The all-reflective optical train is suited to high-magnification observing and lunar/planetary imaging.
Manufacturer model: TS-Optics 203 mm f/12 classical Cassegrain · Specifications checked against manufacturer data on 2026-11-04
