Eyepiece Skywatcher SWA-58 9 mm 1.25 inch 58° apparent field

Skywatcher SWA-58 9 mm eyepiece with a 1.25" barrel and a 58° apparent field is designed for visual astronomy with compatible telescopes. It provides a moderate level of magnification suitable for detailed views of the Moon and planets while maintaining a relatively wide apparent field that helps track objects and frame extended deep-sky targets. The eyepiece fits standard 1.25" focusers and is intended for observers who need a balance between magnification and usable field of view.

Advantages

The 9 mm focal length delivers increased magnification compared with low-power eyepieces while the 58° apparent field provides a comfortable viewing circle without excessive eye positioning constraints. The 1.25" barrel format ensures broad compatibility with most amateur telescopes and accessories. Optical correction in the SWA-58 design reduces coma and edge aberrations typical in simple eyepieces, offering improved sharpness across much of the field.

Suitable for

• Planetary observation (Moon, Mars, Jupiter, Saturn)
• Lunar detail studies and crater observation
• Medium magnification views of smaller deep-sky objects (compact nebulae, globular clusters)
• Visual observing sessions with 1.25" focusers

Key specifications

• Focal length: 9 mm
• Apparent field of view: 58°
• Barrel diameter: 1.25 inches
• Optical design: multi-element SWA configuration for improved edge performance
• Typical use: visual astronomy with refractors, reflectors, and catadioptric telescopes that accept 1.25" eyepieces

How to use

Insert the eyepiece into a clean 1.25" focuser and secure it using the focuser’s set-screw or compression ring. Start with low magnification to locate the target, then switch to the 9 mm eyepiece for increased detail. Allow your eyes a minute to adapt to darkness for best contrast. For highest image quality, ensure the telescope is collimated and cooled to ambient temperature; if using a Barlow lens or diagonal, confirm backfocus compatibility before observing.

Recommendations

Use the SWA-58 9 mm eyepiece under steady atmospheric conditions for best planetary detail. For extended deep-sky objects, pair it with a lower-power eyepiece to frame the target, then return to the 9 mm for focused study. Store the eyepiece in a protective case and clean optical surfaces with appropriate tools only when necessary.