Toscanoptics Cassegrain-Dall Kirkham 231/2650 OTA

Description

Eliminating primary mirror focal shift during high-magnification lunar video capture, the Toscanoptics Cassegrain-Dall Kirkham 231/2650 OTA is a large-aperture planetary and deep-sky research telescope optical tube assembly. Operating at an f/11.5 focal ratio with a long 2650mm focal length, this 231mm (9.09 in) clear aperture instrument delivers a 0.50 arcseconds theoretical resolving power and reaches magnitude 14.3, resolving delicate planetary nebula structures and tight binary systems.

The optical system features a Dall-Kirkham Cassegrain design comprising an elliptical primary mirror and a spherical secondary mirror, yielding a 30% central obstruction by diameter (9.0% by area) from its 69mm secondary assembly. Built inside an Italian carbon fiber tube measuring 680mm in length with a 275mm outer diameter, the assembly provides 180mm of mechanical back focus from the rear cell. Equipped with an external 2-inch dual-speed linear bearing rack-and-pinion focuser and a 360-degree field rotator, this 9.00 kg (19.84 lbs) telescope illuminates a 35mm image circle optimized for APS-C sensors and high-speed planetary video cameras.

Key Features of Toscanoptics Cassegrain-Dall Kirkham 231/2650 OTA

Engineered for high-resolution planetary video astronomy and double-star auditing, this 231mm Dall-Kirkham combines low-expansion mirrors with an external linear bearing focuser. Its lightweight carbon fiber optical tube, CNC-machined aluminum support rings, and 75mm Losmandy-style dovetail bar ensure structural stiffness during long imaging sessions.

• 231mm (9.09 in) clear aperture with long 2650mm focal length and f/11.5 focal ratio
• Dall-Kirkham Cassegrain optics with elliptical primary and spherical secondary mirrors
• Precision annealed Schott BK7 and Suprax glass substrates rated at 1/5 lambda minimum
• Enhanced aluminum optical coatings with 96% reflectivity and quartz protective overcoat
• External 2-inch dual-speed linear bearing rack-and-pinion focuser 1:10 with 360-degree rotator
• Generous 180mm back focus distance measured directly from the rear mechanical cell
• Optimized 35mm image circle tailored for planetary video cameras and APS-C format sensors
• CNC aluminum support rings, 75mm Losmandy-style dovetail bar, and 1.25-inch adapter included

Schott BK7 & Suprax Low-Expansion Optical Train

Utilizing precision annealed Schott BK7 and Suprax optical glass with a minimum surface accuracy of 1/5 lambda peak-to-valley, the mirror system maintains thermal stability during nocturnal temperature shifts. Enhanced aluminum coatings with 96% reflectivity and a quartz overcoat ensure high throughput across practical magnifications from 33.0x up to 462x.

Linear Bearing Focuser & Carbon Fiber Chassis

Because focusing is achieved externally rather than moving the primary mirror, image shift is prevented when recording planetary video sequences. The 2-inch dual-speed linear bearing focuser features a 1:10 micro-reduction drive and a 360-degree manual rotator, while the 275mm diameter carbon fiber tube maintains focus stability under changing ambient temperatures.

• External 2-inch linear bearing rack-and-pinion focuser with 1:10 micro-tuning to prevent mirror shift
• Integrated 360-degree field rotator for framing planetary orientations and sensor positioning
• Rigid carbon fiber tube construction minimizing thermal focal drift during extended imaging runs

Toscanoptics Carbon Custom Cassegrain Warranty

The Toscanoptics Cassegrain-Dall Kirkham 231/2650 OTA is backed by a 2-year limited warranty against material and manufacturing defects. The complete factory package contains the Carbon Fiber Dall-Kirkham OTA, CNC tube rings, Losmandy dovetail bar, 2-inch dual-speed focuser, and a 1.25-inch adapter.