Orion Optics UK AG10 Optical Tube Assembly

Fast f/3.8 Optics with a 50mm Corrected Field

The core of the AG10 is its optical speed. At f/3.8, you can capture deep signal on faint targets in a fraction of the time required by f/8 or f/10 systems. This speed is made usable by a sophisticated 4-lens ED corrector integrated into the optical path. This design delivers a 50mm diameter, fully-corrected image circle, ensuring your images are free of coma and field curvature even on full-frame and larger sensors.

The optical correction is engineered to produce incredibly tight stars, with a measured spot size of only 3.0µm on-axis and 7.2µm at the field edge. This level of correction allows you to take full advantage of the resolving power of modern, small-pixel CMOS and CCD cameras, capturing fine details in distant galaxies and nebulae.

Carbon Fibre Sandwich Tube: 12kg of Thermal Stability

To maintain precise focus through changing temperatures, the AG10 is built with a carbon fibre sandwich tube. This material exhibits a near-zero coefficient of thermal expansion, preventing the 950mm focal length from shifting as the night air cools. The entire optical tube assembly weighs approximately 12kg, placing it within the capacity of many mid-range equatorial mounts.

The tube measures 810mm in length with a 300mm diameter, providing ample rigidity to support the optical components without flexure. All mechanical components, including the mirror cell and mounting hardware, are CNC machined from aluminum for a precise, stable fit.

3-inch Ceres Focuser and 9-Point Mirror Cell

The AG10 is equipped with a robust 3-inch Ceres rack and pinion focuser. This large-aperture focuser is designed to carry heavy imaging trains, including large cameras, filter wheels, and off-axis guiders, without sagging or shifting. The 10:1 dual-speed reduction allows for extremely fine focus adjustments, which is critical for achieving sharp stars at such a fast focal ratio.

The 250mm primary mirror is supported by a 9-point suspension mirror cell, also CNC machined. This cell distributes the weight of the mirror evenly to prevent astigmatism and other optical distortions, preserving the hand-figured quality of the primary optic regardless of the telescope's orientation.

Active Thermal Management: 3 Integrated Cooling Fans

A large primary mirror must reach thermal equilibrium with the ambient air to deliver sharp images. The AG10 accelerates this process with three controllable cooling fans built directly into the rear mirror cell. This active cooling system dramatically reduces the time it takes for the 250mm mirror to acclimate, letting you start imaging sooner and minimizing the effects of tube currents.

Orion Optics AG10 vs. a 10-inch Ritchey-Chrétien Astrograph

Imagers considering a 10-inch astrograph often compare the AG10 Newtonian to a similarly-sized Ritchey-Chrétien (RC). While both are excellent instruments, they serve different priorities.

• Advantage RC: A well-collimated RC offers excellent correction across a large field without a corrector in the optical train and is inherently free of coma. They typically have longer focal lengths, making them well-suited for smaller targets like planetary nebulae and galaxies.
• Advantage AG10: The primary advantage is speed. At f/3.8, the AG10 gathers light over four times faster than a typical f/8 RC, meaning a 5-minute exposure on the AG10 is equivalent to a 20-minute exposure on the RC. The AG10's built-in 4-lens corrector delivers a 50mm flat field out of the box, whereas an RC often requires an additional, costly field flattener or reducer to achieve similar performance.

Comparing the Optical Grades

The images below show the same view of Saturn captured through the included Professional grade and the optional Ultra (Lambda/10 PV) upgrade, under identical conditions -- a visual illustration of the difference in contrast and fine detail the upgrade delivers.

1/6 PV (Professional)

Lambda/10 PV (Ultra)