Secondary Mirror Skywatcher SW-5510 for 305/1500 Newtonian reflector

Secondary Mirror Skywatcher SW-5510 for 305/1500 Newtonian reflector is a replacement elliptical secondary mirror sized to fit a 305 mm aperture, 1500 mm focal length Newtonian optical tube. It redirects the converging light cone from the primary mirror toward the focuser and eyepiece, restoring correct optical alignment and image formation in compatible Skywatcher Newtonian reflectors. This spare part is intended for maintenance, repair, or upgrade of the telescope’s secondary assembly and supports standard collimation procedures used with Newtonian designs.

Advantages

The secondary mirror is manufactured to match the geometry and optical layout of a 305/1500 Newtonian system, providing a reflective surface and shape necessary for correct light redirection and minimal vignetting. It offers a practical option for replacing a worn, damaged, or misaligned secondary without modifying the primary mirror or focuser. Installation restores the intended focal path and allows routine collimation to achieve accurate star images and efficient light throughput.

Suitable for

• Repairing a Skywatcher 305 mm (12") Newtonian reflector with 1500 mm focal length
• Replacing a damaged or degraded secondary mirror in compatible Newtonian tubes
• Keeping as a spare part for field maintenance or observatory use
• Upgrading or restoring optical alignment after tube servicing

Key specifications

• Designed for Newtonian reflectors with 305 mm aperture and 1500 mm focal length
• Elliptical secondary mirror geometry matched to the optical layout
• Reflective surface suitable for visible-light astronomy
• Form and size intended to minimize vignetting and preserve focal ratio
• Compatible with standard secondary holders and spider assemblies used on Skywatcher Newtonians

How to use

Remove the existing secondary mirror assembly from the secondary holder or spider according to the telescope manufacturer’s instructions, taking care to note the current rotation and tilt orientation. Mount the replacement secondary mirror in the holder and secure it without overtightening. Perform an initial rough alignment by centering the secondary under the focuser and adjusting the tilt so the primary mirror is visible and centered. Complete the process with a standard collimation routine—using a laser collimator, Cheshire eyepiece, or star test—to fine-tune the alignment for optimal image quality.

Recommendations

Handle the mirror by the edges and avoid touching the reflective surface. Keep the mirror covered or stored in protective padding when not installed. After installation, check collimation before each observing session and perform cleaning only when necessary, using appropriate optical cleaning materials to avoid damaging coatings.