Orion Optics UK ODK10Tr Truss Optical Tube Assembly

Corrected Dall-Kirkham: 50mm Flat Field with 3.5μm Spot Sizes

The heart of the ODK10Tr is its optical system, which pairs an elliptical primary mirror with a spherical secondary and a dedicated 3-lens corrector. This design produces a 50mm diameter, fully illuminated and corrected image circle, free of coma and field curvature. You can confidently use full-frame (35mm format) sensors and even larger medium-format chips without vignetting or distorted stars at the corners.

The optical correction delivers incredibly tight star images, with a measured spot size of only 3.5μm at the center of the field and 6.2μm at the very edge. This level of correction ensures that the telescope's resolution, not the optics, is the limiting factor, resolving fine detail in galaxies and nebulae even with small-pixel CMOS cameras.

Carbon Fiber Truss: 12kg of Rigid, Stable Construction

The ODK10Tr's open truss structure, built from a carbon fiber sandwich material, provides a superior stiffness-to-weight ratio. At just 12kg, this 10-inch astrograph is manageable for a wide range of equatorial mounts while remaining exceptionally rigid to prevent flexure as it moves across the sky. Carbon fiber's low thermal expansion coefficient also ensures the 1700mm focal length remains stable during temperature drops, minimizing focus shift throughout an imaging session.

• Active Cooling: Three integrated, controllable fans are mounted behind the primary mirror to accelerate thermal acclimation, allowing you to start imaging faster.
• CNC Machined Components: Key mechanical parts, including the honeycomb mirror cell and dovetail plate supports, are CNC machined from aluminum for precise, repeatable alignment and durability.
• Stray Light Control: While the open truss design promotes rapid cooling, it is susceptible to stray light. Using a simple fabric shroud (not included) is recommended to maximize image contrast, especially from light-polluted locations.

Imaging-Ready Mechanics: 3" Focuser and 213mm Back Focus

Engineered for demanding imaging setups, the ODK10Tr features a robust 3" Crayford focuser with a 10:1 reduction ratio for precise fine adjustments. The large-diameter drawtube eliminates vignetting with large sensors and can support heavy camera packages without slipping or tilting. With a generous 213mm of back focus measured from the rear of the mirror cell, you have ample room to install complex imaging trains, including off-axis guiders, large filter wheels, and camera rotators, without concern for reaching focus.

ODK10Tr vs. Ritchey-Chrétien: Collimation, Field Correction, and Spot Size

For imagers seeking a flat-field instrument, the main alternative to an ODK is a Ritchey-Chrétien (RC). While both are excellent designs, the ODK presents several practical advantages.

• Competitor's Advantage (RC): A pure RC design is naturally free from coma, an optical aberration that elongates stars away from the center. However, it suffers from significant astigmatism and field curvature, requiring a separate corrector for serious imaging.
• ODK10Tr Advantage: The ODK's integrated 3-lens corrector fully addresses coma, astigmatism, and field curvature across its 50mm image circle. More importantly, the ODK's spherical secondary mirror makes collimation far more forgiving than the hyperbolic secondary of an RC, which requires extremely precise alignment. For most users, the ODK delivers superior edge-of-field star shapes and is significantly easier to maintain in perfect adjustment.