Type:	RC Optical Systems Carbon Fiber Ritchey-Chrétien
Objective Diameter:	12.5 inches, 317.5mm
Focal Length:	112.5 inches, 2857.5mm
Focal Ratio:	F/9

The RCOS is a used, 2000 model. I purchased it to replace the 14" Meade LX200 mainly because I wanted to start using a CCD with a larger chip than the ST10MXE and the LX200 would have too much coma and field curvature to cover a larger CCD chip.

The RCOS has a carbon fiber tube which is both a blessing and a curse. The blessing is that it the focus stays constant with temperature changes (and at my elevation of 8600 feet, the temperature changes quite a bit during the night). The curse is that it takes longer to reach the ambient temperature. Fortunately, the RCOS has built in fans that allow it to maintain the ambient temperature once it is initially reached. The fans also maintain a laminar air flow near the tube, reducing the turbulance inside the tube which would normally degrade the image quality. Tube currents were a constant problem with the LX200.

Because my ST10MXE has very small (6.8u) pixels, the image scale the ST10MXE and RCOS at F/9 is very oversampled* most of the time. Because of this, I often use an AP 0.67 focal reducer when using the ST10MXE with the RCOS. This yields a focal length of about 81 inches (2057mm) and a focal ratio of about 6.5. The new STL11000 has larger pixels (9u) so I don't anticipate using a focal reducer with it.

* Note - just what constitutes oversampling and it's effects is a much debated topic.