The 8" Astro-Tech RC differs from the 6" version in the following ways:

• Aperture: 8" 1928mm focal length, f/9 focal ratio.
• Primary mirror: Made of low thermal expansion quartz. Polished to 1/12th wave or better surface accuracy. Unlike designs that move the primary mirror fore and aft in the optical tube to focus (which can lead to image shift as the mirror position changes) the AT8RC primary mirror is fixed to eliminate image shift and focus changes.
• Secondary mirror: Made of low thermal expansion quartz. Polished to 1/12th wave or better surface accuracy. Mounted in a four-vane spider and fully collimatable using simple standard Schmidt-Cassegrain collimating techniques. Unlike complicated R-C designs that use motors to move the secondary mirror fore and aft to focus, the AT8RC secondary mirror is fixed, and focusing is done externally.
• Dielectric coated optics: Both primary and secondary mirrors have non-tarnishing state-of-the-art dielectric mirror coatings. These have a full 99% reflectivity for the brightest possible images. This is substantially higher than the 88% reflectivity of conventional aluminium coatings or the 94-96% reflectivity of enhanced aluminium coatings.

• Carbon Fibre Optical tube: Made of light high strength woven carbon fibre-reinforced composite with extremely low thermal expansion characteristics to reduce the possibility of temperature-related focus changes. Die-cast and machined aluminium front and rear cells. The 9" OD x 20.25" long carbon fibre tube is virtually indestructible. The use of a carbon fibre composite reduces the weight of the optical tube with no loss of strength or rigidity compared to an aluminium tube. Because of the use of a carbon fibre optical tube, the weight of this 8" R-C is only a little more than two pounds heavier than the aluminium tube 6" Astro-Tech RC.
• Internal light baffles: Computer optimized primary and secondary baffling. Eight contrast-enhancing glare-stop baffles in the optical tube, multiple glare-stop micro baffles in the secondary mirror light shield, and four baffles in the primary mirror baffle tube provide truly dark sky backgrounds during imaging.
• Dual-speed micro fine Feather Touch Crayford focuser: The precision-made non-Vignetting focuser is a genuine Starlight Instruments Feather Touch focuser which is the finest and most reliable focuser available to the amateur astronomer. The focuser has dual-speed focusing. There are two coarse focusing knobs. The right knob also has a smaller concentric knob with a 10:1 reduction gear micro fine focusing ratio. This provides exceptionally precise image control during critical 35mm or CCD imaging. All focus knobs are ribbed, so they are easy to operate, even while wearing gloves or mittens in cold weather. Multiple internal baffles in the focuser drawtube assure high contrast.