Orion Optics UK CT12L Optical Tube Assembly
- 300mm (12") Aperture
- 1590mm Focal Length, f/5.3 Focal Ratio
- Standard 1/10 PV Wavefront Optics
- Carbon Fibre Sandwich Tube Construction
- 2" Focuser with Reduction Gearing
- 9-Point CNC Machined Mirror Cell
Simulate the exact field of view of the Orion Optics UK CT12L Optical Tube Assembly with your specific telescope.
Launch Visual Assistant
Simulate the exact field of view of the Orion Optics UK CT12L Optical Tube Assembly with your specific telescope.
Launch Imaging AssistantThe Orion Optics UK CT12L is an imaging-first Newtonian built around a 300mm primary mirror hand-figured to a 1/10 PV wavefront standard. Its 1590mm focal length delivers an f/5.3 ratio, ideal for resolving fine detail on planets and capturing faint structures in deep-sky objects. The entire optical system is housed in a 1450mm carbon fibre sandwich tube weighing approximately 20kg, ensuring thermal stability and maintaining a precise focal plane through long imaging sessions.
The heart of the CT12L is its 300mm Suprax primary mirror, which comes standard with Orion Optics UK's highest optical certification: a 1/10 PV wavefront accuracy. This is not an optional upgrade but the baseline for the CT series, ensuring the highest possible contrast and sharpness. The mirror features Enhanced Hilux coatings for maximum reflectivity, and its performance is documented by an included Zygo interferometry report, providing empirical proof of its quality.
To maintain the performance of its elite optics, the CT12L employs a carbon fibre sandwich tube. This advanced material has a near-zero coefficient of thermal expansion, preventing the 1590mm focal length from shifting as ambient temperature changes. The 350mm diameter tube is finished with a gloss exterior and a matte black interior to suppress stray light, providing a high-contrast backdrop for both visual observation and astrophotography.
The CT12L's optical performance is supported by a robust mechanical framework. The primary mirror rests on a CNC machined 9-point flotation cell that prevents flexure and is aided by a fan for rapid thermal equalization. Up front, the 63mm secondary mirror is held by a fully adjustable, stainless steel 4-vane spider, while the 2-inch focuser with reduction gearing allows for the precise, repeatable focus adjustments necessary at an f/5.3 focal ratio.
Orion Optics UK offers several grades of optical accuracy, but the CT12L includes their finest 1/10 PV grade as standard. Compared to a common 1/4 PV "diffraction-limited" mirror, a 1/10 PV surface delivers a wavefront that is significantly closer to a perfect parabola. In practice, this translates to visibly higher contrast on planetary details like Jupiter's cloud bands, tighter star points, and the ability to resolve fainter, more subtle nebulosity that would be lost in the noise of a less accurate system.
The 1/10 Peak-to-Valley (PV) wavefront rating means the surface of the 300mm primary mirror deviates from a perfect parabola by no more than 1/10th of a wavelength of light. This is an extremely high standard of accuracy that results in superior image contrast and sharpness. For you, the observer, this means seeing finer details on planets, resolving tighter double stars, and capturing more delicate structures in nebulae.
The carbon fiber tube has a near-zero thermal expansion coefficient. During a long imaging session, as temperatures drop overnight, a metal tube will contract and slightly change the focal length, causing images to lose focus. The CT12L's 1450mm carbon fiber tube remains dimensionally stable, keeping the focal plane locked and ensuring your images remain sharp from the beginning of the night to the end without constant refocusing.
At approximately 20kg for the tube and 2kg for the rings, the CT12L is a substantial instrument. While it can be transported to a dark sky site, it is not a grab-and-go telescope. It requires a robust equatorial mount and is best suited for a semi-permanent or observatory setup where its weight can be managed safely.
With a combined weight of over 22kg (48.5 lbs) for the OTA and rings, plus the added weight of a camera, guide scope, and other accessories, you will need a heavy-duty equatorial mount. A mount with a rated payload capacity of at least 60-70 lbs is recommended to ensure stability for long-exposure astrophotography with the CT12L's 1590mm focal length.
The CT12L's combination of a large 300mm aperture and a fast f/5.3 focal ratio is excellent for galaxy clusters. The large aperture gathers significant light to reveal faint extensions and dust lanes in galaxies like M65 and M66, while the 1/10 PV optics ensure that the faint signal is rendered with maximum contrast against the sky background, making subtle details more visible.
Under steady seeing conditions, the 300mm aperture and 1/10 PV optics of the CT12L will provide exceptional planetary views. On Saturn, you can expect to clearly resolve the Cassini Division, subtle cloud banding on the planet's disk, and potentially the Encke Gap with excellent seeing. The high-contrast optics will also make it easier to pick out Saturn's fainter moons against the glare of the rings.
| Optics Grade | 1/10 PV wavefront |
| Aperture | 300mm |
| Focal Length | 1590mm |
| Focal Ratio | f/5.3 |
| Primary Mirror | Suprax with Enhanced Hilux Coatings |
| Secondary Mirror Size | 63mm |
| Focuser | 2" with reduction gearing |
| Finder Scope | 8x50 |
| Tube Material | Carbon fibre sandwich |
| Tube Diameter | 350mm |
| Tube Length | 1450mm |
| Tube Weight | 20kg (approx) |
| Mirror Cell | 9-point suspension, CNC machined aluminum |
| Spider | 4-vane, stainless steel, fully adjustable |
| Secondary Holder | Machined aluminum, rotatable |
| Rings | CNC machined tube rings, anodised black |
| Rings Weight | 2kg |
| Extension Tubes | 40mm long, screw threaded |
| Boxed Dimensions | Box 1: 172x58x58mm, Box 2: 58x58x34mm |
| Boxed Weight | Box 1: 18.5kg, Box 2: 12kg |
CT12L Optical Tube Assembly
× 1
8x50 Finder Scope
× 1
CNC Machined Tube Rings
× 1 Pair
40mm Extension Tube
× 1
Zygo Interferometry Test Report
× 1