Coma Corrector Skywatcher SW-5417 2" — aplanatic 2-inch optical accessory

The Coma Corrector Skywatcher SW-5417 2" is an aplanatic optical accessory designed for telescopes with 2-inch focuser systems. It reduces coma and other off-axis aberrations to deliver flatter fields and more accurate star shapes toward the edges of the image. Optimized for both astrophotography and visual observing, this corrector improves image quality across the frame while preserving native focal ratio and maintaining straightforward mechanical integration with standard 2" focusers.

Advantages

This coma corrector provides aplanatic correction that reduces star elongation and improves edge sharpness across a wide field, making it easier to capture usable data from the full sensor area. It is compatible with typical 2-inch focuser setups and does not require complex optical reconfiguration. The design keeps central image quality intact while noticeably improving off-axis performance, which benefits long-exposure imaging and wide-field compositions.

Suitable for

• Wide-field astrophotography with refractors and reflectors using a 2" focuser
• Visual observing when improved edge sharpness for star fields is required
• Imaging where uniform point‑source rendering across the frame is important
• Users upgrading their optical train to reduce coma without changing focal ratio

Key specifications

• Format: 2-inch barrel compatible with standard 2" focusers
• Optical correction: aplanatic coma correction for improved off-axis performance
• Application: designed for both photographic and visual use
• Field performance: produces flatter field and reduced star elongation toward frame edges
• Mechanical: straightforward in-line installation between eyepiece or camera adapter and focuser

How to use

Install the SW-5417 coma corrector into the 2" focuser and secure it in the drawtube following your focuser manufacturer's recommendations. Attach the camera adapter or eyepiece to the corrector's rear cell and adjust back focus according to the telescope and detector combination to achieve optimal focus across the field. For imaging, start with the manufacturer-recommended spacing or use small focus adjustments while observing star shapes near the frame edge to fine-tune correction. For visual use, confirm comfortable focusing and parfocality with eyepieces if swapping between eyepiece and camera setups.

Usage recommendations

To obtain the best results, verify the correct spacing between the telescope focus plane and the camera sensor or eyepiece; small adjustments can significantly affect corner star shapes. Perform test exposures at different focus positions and evaluate star roundness toward the edges. Use the corrector with well-collimated optics and stable mounting to maximize the improvement in wide-field image quality.